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Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) Bachelor of Science with Honours (Aquatic Resource Science and Management) 2016

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Water Quality at Bakun HEP Reservoir Belaga Sarawak

WiUieKoh

(44620)

Bachelor of Science with Honours (Aquatic Resource Science and Management)

2016

Pusat 1 UNM

1111111111111111111111111 1000272665

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Willie Koh (44620)

This dissertation is submitted in partial fulfilment of the requirements for the degree of

Bachelor of Science with Honours in Aquatic Resource Science and Management

Faculty of Resource Science and Technology

Universiti Malaysia Sarawak

2016

DECLARATION OF AUTHORSHIP

I Willie Koh declare that the final year project report entitled

Water Quality at Bakun HEP Reservoir Belaga Sarawak

and the work presented in the report are both my own and have been generated by me as

the result of my own original research I confirm that

bull this work was done wholly or mainly while in candidature for a research degree at

bull this University

bull where I have made corrections based on suggestion by supervisor and examiners

bull this has been clearly stated

bull where I have consulted the published work of others this IS always clearly

attributed

bull where I have quoted from the work of others the source is always given With the

bull exception of such quotations this report is entirely my own work

bull I have acknowledged all main sources of help

bull where the thesis is based on work done by myself jointly with others I have made

bull clear exactly what was done by others and what I have contributed myself

bull none of this work has been published before submission

Signed

Aquatic Resource Science and Management Department of Aquatic Science Faculty of Resource Science and Technology Universiti Malaysia Sarawak (UNIMAS)

I

ACKNOWLEDGMENT

My utmost gratitude and thanks to my supervisor Professor Dr Lee Nyanti Janti

ak Chukong for his valuable advice suggestions guidance constructive criticisms and

commitment from the start of this research until the final submission of this thesis

Besides that a special thanks to my co-supervisor Associate Professor Dr Ling Teck Vee

on the guidance and support

I would also like to express my appreciation to the staff of the Department of

Aquatic Science Mr Benedict ak Samling and Mr Richard Toh for their friendly help

and facilitation during the field work and laboratory work Not forgetting my fellow peers

who helped me and for their valuable support Also special thanks to my seniors Angie

Sapis and Ahmad Aklunal Atan for the precious advice Without their kind support and

technical assistance it would not be an easy task to complete this study Also warmest

regards and thanks to Mr Laing and his family for providing us a comfortable

accommodation during our field work in Bakun

Special thanks also goes to Sarawak Energy Berhand for the financial assistance in

this study through the research grant no GL (F07)SEB4A12013 (24)

Finally my family members are highly acknowledged for their understanding and

never ending support To those who indirectly contribute to this research your kindness is

greatly appreciated All praises to God for the strength and opportunity for completing this

thesis Without his mercy I may not be able to go through the tough times in the course of

this study

II

i

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Abstract

Since the water supply at Bakun Hydroelectric Dam reached its full supply level only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started At each station water in triplicate samples were collected at 6 levels which is the subsurface at 10m 20m 30m 40m and 50m depth Results showed that thermocline occurred at 3m to 10m depth at all stations DO at the subsurface (499 - 610 mgL) dropped drastically to anoxic level starting from 2m to 10m depth at all stations Water conductivity and turbidity increases while pH decreased as depth increased The highest chlorophyll-a (1168 J-lgL) was recorded at 10m depth with positive correlation with turbidity Increasing levels of ammonia-nitrogen (00533 - 06400 mgL) total suspended solids (330 - 6306 mgL) and five-day biochemical oxygen demand (186 - 430 mgL) were observed while depth increases Nitrate (001 - 022 mgL) nitrite (00020 - 01170 mgL) silica (039 - 154 mgL) and orthophosphate (00900 - 17067 mgL) showed different variations with depth This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started

Keywords hydroelectric dam turbidity water quality nutrients

Abstrak

Sejak bekalan air di Empangan Hidroelektrik Bakun mencapai tahap penuh hanya satu kajian telah dijalankan semasa fasa pengisian iaitu 3 tahun dan 10 bulan lebih awal daripada kajian ini Disebabkan air di dalam empangan adalah sangat penting untuk organisma akuatik di dalam empangan dan bawah empangan satu kajian telah dijalankan di 3 stesen untuk mengenalpasti parameter kualiti air 5 tahun selepas penakungan bermula Di setiap stesen air telah diambil sebanyak tiga kali daripada 6 tahap iaitu subpermukaan 10m 20m 30m 40m dan 50m Hasil kajian menunjuk perbentukan termoklin pada kedalaman dari 3m ke 10m di semua stesen DO di subpermukaan (499shy610 mglL) menurun dengan drastik kepada tahap anoksik bermula pada kedalaman 2m ke 10m di semua stesen Konduktiviti air dan kekeruhan meningkat dan pH menurun dengan kedalaman Klorofil-a paling tinggi (1168 pgIL) adalah pada kedalaman 10m dan berkorelasi positijdengan kekeruhan air Peningkatan tahap ammonia-nitrogen (00533 shy06400 mgIL) jumlah pepejal terampai (330 - 6306 mgIL) dan keperluan oksigen biokimia selepas lima hari (186 - 430 mglL) meningkat apabila kedalaman meningkat Nitrat (001 - 022 mgIL) nitrit (00020 - 01170 mgIL) silika (039 - 154 mglL) dan ortofosfat (00900 - 17067 mglL) menunjukkan variasi yang berbeza dengan kedalaman Kajian ini menunjukkan bahawa kualiti air di Empangan Hidroelektrik Bakun bertambah baik dan masih berubah berbanding dengan kajian semasa fasa pengisian dan belum lagi staNI selepas 5 tahun dan 6 bulan sejak penakungan bermula

Kata kunci empangan hidroelektrik kekeruhan air kualiti air nutrien

III

Pusat Khidmat Maklumal Akadtmi UNIVEftSm MALAYSIA SAKAWA

TABLE OF CONTENTS

Declaration of Authorship

Acknowledgement

Abstract

Abstrak

Table of Contents

List of Figures

List of Tables

List of Abbreviations

10 Introduction

20 Literature Review

21 Reservoir

22 Water Quality

221 Temperature

222 Dissolved Oxygen (DO)

223 pH

224 Nutrients

23 Impact of Hydroelectric Dams on Water Quality

30 Materials and Methods

31 Study Site

32 Water Samples

33 Water Quality Parameters Measured In-situ

34 Water Quality Parameters Analysed Ex-situ

341 Biological Oxygen Demand (BODs)

342 Total Suspended Solids (TSS)

343 Chlorophyll-a

344 Ammonia-Nitrogen (NH3-N)

345 Nitrate (N03-)

346 Nitrite (N02-)

347 Orthophosphate (P043-)

348 Silica (Si04)

35 Statistical Analyses

Page

I

II

III

III

IV

VI

VII

VIII

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IV

18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

v

I

Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

-

LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 2: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Pusat 1 UNM

1111111111111111111111111 1000272665

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Willie Koh (44620)

This dissertation is submitted in partial fulfilment of the requirements for the degree of

Bachelor of Science with Honours in Aquatic Resource Science and Management

Faculty of Resource Science and Technology

Universiti Malaysia Sarawak

2016

DECLARATION OF AUTHORSHIP

I Willie Koh declare that the final year project report entitled

Water Quality at Bakun HEP Reservoir Belaga Sarawak

and the work presented in the report are both my own and have been generated by me as

the result of my own original research I confirm that

bull this work was done wholly or mainly while in candidature for a research degree at

bull this University

bull where I have made corrections based on suggestion by supervisor and examiners

bull this has been clearly stated

bull where I have consulted the published work of others this IS always clearly

attributed

bull where I have quoted from the work of others the source is always given With the

bull exception of such quotations this report is entirely my own work

bull I have acknowledged all main sources of help

bull where the thesis is based on work done by myself jointly with others I have made

bull clear exactly what was done by others and what I have contributed myself

bull none of this work has been published before submission

Signed

Aquatic Resource Science and Management Department of Aquatic Science Faculty of Resource Science and Technology Universiti Malaysia Sarawak (UNIMAS)

I

ACKNOWLEDGMENT

My utmost gratitude and thanks to my supervisor Professor Dr Lee Nyanti Janti

ak Chukong for his valuable advice suggestions guidance constructive criticisms and

commitment from the start of this research until the final submission of this thesis

Besides that a special thanks to my co-supervisor Associate Professor Dr Ling Teck Vee

on the guidance and support

I would also like to express my appreciation to the staff of the Department of

Aquatic Science Mr Benedict ak Samling and Mr Richard Toh for their friendly help

and facilitation during the field work and laboratory work Not forgetting my fellow peers

who helped me and for their valuable support Also special thanks to my seniors Angie

Sapis and Ahmad Aklunal Atan for the precious advice Without their kind support and

technical assistance it would not be an easy task to complete this study Also warmest

regards and thanks to Mr Laing and his family for providing us a comfortable

accommodation during our field work in Bakun

Special thanks also goes to Sarawak Energy Berhand for the financial assistance in

this study through the research grant no GL (F07)SEB4A12013 (24)

Finally my family members are highly acknowledged for their understanding and

never ending support To those who indirectly contribute to this research your kindness is

greatly appreciated All praises to God for the strength and opportunity for completing this

thesis Without his mercy I may not be able to go through the tough times in the course of

this study

II

i

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Abstract

Since the water supply at Bakun Hydroelectric Dam reached its full supply level only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started At each station water in triplicate samples were collected at 6 levels which is the subsurface at 10m 20m 30m 40m and 50m depth Results showed that thermocline occurred at 3m to 10m depth at all stations DO at the subsurface (499 - 610 mgL) dropped drastically to anoxic level starting from 2m to 10m depth at all stations Water conductivity and turbidity increases while pH decreased as depth increased The highest chlorophyll-a (1168 J-lgL) was recorded at 10m depth with positive correlation with turbidity Increasing levels of ammonia-nitrogen (00533 - 06400 mgL) total suspended solids (330 - 6306 mgL) and five-day biochemical oxygen demand (186 - 430 mgL) were observed while depth increases Nitrate (001 - 022 mgL) nitrite (00020 - 01170 mgL) silica (039 - 154 mgL) and orthophosphate (00900 - 17067 mgL) showed different variations with depth This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started

Keywords hydroelectric dam turbidity water quality nutrients

Abstrak

Sejak bekalan air di Empangan Hidroelektrik Bakun mencapai tahap penuh hanya satu kajian telah dijalankan semasa fasa pengisian iaitu 3 tahun dan 10 bulan lebih awal daripada kajian ini Disebabkan air di dalam empangan adalah sangat penting untuk organisma akuatik di dalam empangan dan bawah empangan satu kajian telah dijalankan di 3 stesen untuk mengenalpasti parameter kualiti air 5 tahun selepas penakungan bermula Di setiap stesen air telah diambil sebanyak tiga kali daripada 6 tahap iaitu subpermukaan 10m 20m 30m 40m dan 50m Hasil kajian menunjuk perbentukan termoklin pada kedalaman dari 3m ke 10m di semua stesen DO di subpermukaan (499shy610 mglL) menurun dengan drastik kepada tahap anoksik bermula pada kedalaman 2m ke 10m di semua stesen Konduktiviti air dan kekeruhan meningkat dan pH menurun dengan kedalaman Klorofil-a paling tinggi (1168 pgIL) adalah pada kedalaman 10m dan berkorelasi positijdengan kekeruhan air Peningkatan tahap ammonia-nitrogen (00533 shy06400 mgIL) jumlah pepejal terampai (330 - 6306 mgIL) dan keperluan oksigen biokimia selepas lima hari (186 - 430 mglL) meningkat apabila kedalaman meningkat Nitrat (001 - 022 mgIL) nitrit (00020 - 01170 mgIL) silika (039 - 154 mglL) dan ortofosfat (00900 - 17067 mglL) menunjukkan variasi yang berbeza dengan kedalaman Kajian ini menunjukkan bahawa kualiti air di Empangan Hidroelektrik Bakun bertambah baik dan masih berubah berbanding dengan kajian semasa fasa pengisian dan belum lagi staNI selepas 5 tahun dan 6 bulan sejak penakungan bermula

Kata kunci empangan hidroelektrik kekeruhan air kualiti air nutrien

III

Pusat Khidmat Maklumal Akadtmi UNIVEftSm MALAYSIA SAKAWA

TABLE OF CONTENTS

Declaration of Authorship

Acknowledgement

Abstract

Abstrak

Table of Contents

List of Figures

List of Tables

List of Abbreviations

10 Introduction

20 Literature Review

21 Reservoir

22 Water Quality

221 Temperature

222 Dissolved Oxygen (DO)

223 pH

224 Nutrients

23 Impact of Hydroelectric Dams on Water Quality

30 Materials and Methods

31 Study Site

32 Water Samples

33 Water Quality Parameters Measured In-situ

34 Water Quality Parameters Analysed Ex-situ

341 Biological Oxygen Demand (BODs)

342 Total Suspended Solids (TSS)

343 Chlorophyll-a

344 Ammonia-Nitrogen (NH3-N)

345 Nitrate (N03-)

346 Nitrite (N02-)

347 Orthophosphate (P043-)

348 Silica (Si04)

35 Statistical Analyses

Page

I

II

III

III

IV

VI

VII

VIII

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4

5

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6

7

9

9

11

11

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12

13

14

14

15

16

16

17

IV

18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

v

I

Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

-

LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 3: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

DECLARATION OF AUTHORSHIP

I Willie Koh declare that the final year project report entitled

Water Quality at Bakun HEP Reservoir Belaga Sarawak

and the work presented in the report are both my own and have been generated by me as

the result of my own original research I confirm that

bull this work was done wholly or mainly while in candidature for a research degree at

bull this University

bull where I have made corrections based on suggestion by supervisor and examiners

bull this has been clearly stated

bull where I have consulted the published work of others this IS always clearly

attributed

bull where I have quoted from the work of others the source is always given With the

bull exception of such quotations this report is entirely my own work

bull I have acknowledged all main sources of help

bull where the thesis is based on work done by myself jointly with others I have made

bull clear exactly what was done by others and what I have contributed myself

bull none of this work has been published before submission

Signed

Aquatic Resource Science and Management Department of Aquatic Science Faculty of Resource Science and Technology Universiti Malaysia Sarawak (UNIMAS)

I

ACKNOWLEDGMENT

My utmost gratitude and thanks to my supervisor Professor Dr Lee Nyanti Janti

ak Chukong for his valuable advice suggestions guidance constructive criticisms and

commitment from the start of this research until the final submission of this thesis

Besides that a special thanks to my co-supervisor Associate Professor Dr Ling Teck Vee

on the guidance and support

I would also like to express my appreciation to the staff of the Department of

Aquatic Science Mr Benedict ak Samling and Mr Richard Toh for their friendly help

and facilitation during the field work and laboratory work Not forgetting my fellow peers

who helped me and for their valuable support Also special thanks to my seniors Angie

Sapis and Ahmad Aklunal Atan for the precious advice Without their kind support and

technical assistance it would not be an easy task to complete this study Also warmest

regards and thanks to Mr Laing and his family for providing us a comfortable

accommodation during our field work in Bakun

Special thanks also goes to Sarawak Energy Berhand for the financial assistance in

this study through the research grant no GL (F07)SEB4A12013 (24)

Finally my family members are highly acknowledged for their understanding and

never ending support To those who indirectly contribute to this research your kindness is

greatly appreciated All praises to God for the strength and opportunity for completing this

thesis Without his mercy I may not be able to go through the tough times in the course of

this study

II

i

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Abstract

Since the water supply at Bakun Hydroelectric Dam reached its full supply level only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started At each station water in triplicate samples were collected at 6 levels which is the subsurface at 10m 20m 30m 40m and 50m depth Results showed that thermocline occurred at 3m to 10m depth at all stations DO at the subsurface (499 - 610 mgL) dropped drastically to anoxic level starting from 2m to 10m depth at all stations Water conductivity and turbidity increases while pH decreased as depth increased The highest chlorophyll-a (1168 J-lgL) was recorded at 10m depth with positive correlation with turbidity Increasing levels of ammonia-nitrogen (00533 - 06400 mgL) total suspended solids (330 - 6306 mgL) and five-day biochemical oxygen demand (186 - 430 mgL) were observed while depth increases Nitrate (001 - 022 mgL) nitrite (00020 - 01170 mgL) silica (039 - 154 mgL) and orthophosphate (00900 - 17067 mgL) showed different variations with depth This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started

Keywords hydroelectric dam turbidity water quality nutrients

Abstrak

Sejak bekalan air di Empangan Hidroelektrik Bakun mencapai tahap penuh hanya satu kajian telah dijalankan semasa fasa pengisian iaitu 3 tahun dan 10 bulan lebih awal daripada kajian ini Disebabkan air di dalam empangan adalah sangat penting untuk organisma akuatik di dalam empangan dan bawah empangan satu kajian telah dijalankan di 3 stesen untuk mengenalpasti parameter kualiti air 5 tahun selepas penakungan bermula Di setiap stesen air telah diambil sebanyak tiga kali daripada 6 tahap iaitu subpermukaan 10m 20m 30m 40m dan 50m Hasil kajian menunjuk perbentukan termoklin pada kedalaman dari 3m ke 10m di semua stesen DO di subpermukaan (499shy610 mglL) menurun dengan drastik kepada tahap anoksik bermula pada kedalaman 2m ke 10m di semua stesen Konduktiviti air dan kekeruhan meningkat dan pH menurun dengan kedalaman Klorofil-a paling tinggi (1168 pgIL) adalah pada kedalaman 10m dan berkorelasi positijdengan kekeruhan air Peningkatan tahap ammonia-nitrogen (00533 shy06400 mgIL) jumlah pepejal terampai (330 - 6306 mgIL) dan keperluan oksigen biokimia selepas lima hari (186 - 430 mglL) meningkat apabila kedalaman meningkat Nitrat (001 - 022 mgIL) nitrit (00020 - 01170 mgIL) silika (039 - 154 mglL) dan ortofosfat (00900 - 17067 mglL) menunjukkan variasi yang berbeza dengan kedalaman Kajian ini menunjukkan bahawa kualiti air di Empangan Hidroelektrik Bakun bertambah baik dan masih berubah berbanding dengan kajian semasa fasa pengisian dan belum lagi staNI selepas 5 tahun dan 6 bulan sejak penakungan bermula

Kata kunci empangan hidroelektrik kekeruhan air kualiti air nutrien

III

Pusat Khidmat Maklumal Akadtmi UNIVEftSm MALAYSIA SAKAWA

TABLE OF CONTENTS

Declaration of Authorship

Acknowledgement

Abstract

Abstrak

Table of Contents

List of Figures

List of Tables

List of Abbreviations

10 Introduction

20 Literature Review

21 Reservoir

22 Water Quality

221 Temperature

222 Dissolved Oxygen (DO)

223 pH

224 Nutrients

23 Impact of Hydroelectric Dams on Water Quality

30 Materials and Methods

31 Study Site

32 Water Samples

33 Water Quality Parameters Measured In-situ

34 Water Quality Parameters Analysed Ex-situ

341 Biological Oxygen Demand (BODs)

342 Total Suspended Solids (TSS)

343 Chlorophyll-a

344 Ammonia-Nitrogen (NH3-N)

345 Nitrate (N03-)

346 Nitrite (N02-)

347 Orthophosphate (P043-)

348 Silica (Si04)

35 Statistical Analyses

Page

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III

IV

VI

VII

VIII

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IV

18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

v

I

Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

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LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 4: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

ACKNOWLEDGMENT

My utmost gratitude and thanks to my supervisor Professor Dr Lee Nyanti Janti

ak Chukong for his valuable advice suggestions guidance constructive criticisms and

commitment from the start of this research until the final submission of this thesis

Besides that a special thanks to my co-supervisor Associate Professor Dr Ling Teck Vee

on the guidance and support

I would also like to express my appreciation to the staff of the Department of

Aquatic Science Mr Benedict ak Samling and Mr Richard Toh for their friendly help

and facilitation during the field work and laboratory work Not forgetting my fellow peers

who helped me and for their valuable support Also special thanks to my seniors Angie

Sapis and Ahmad Aklunal Atan for the precious advice Without their kind support and

technical assistance it would not be an easy task to complete this study Also warmest

regards and thanks to Mr Laing and his family for providing us a comfortable

accommodation during our field work in Bakun

Special thanks also goes to Sarawak Energy Berhand for the financial assistance in

this study through the research grant no GL (F07)SEB4A12013 (24)

Finally my family members are highly acknowledged for their understanding and

never ending support To those who indirectly contribute to this research your kindness is

greatly appreciated All praises to God for the strength and opportunity for completing this

thesis Without his mercy I may not be able to go through the tough times in the course of

this study

II

i

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Abstract

Since the water supply at Bakun Hydroelectric Dam reached its full supply level only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started At each station water in triplicate samples were collected at 6 levels which is the subsurface at 10m 20m 30m 40m and 50m depth Results showed that thermocline occurred at 3m to 10m depth at all stations DO at the subsurface (499 - 610 mgL) dropped drastically to anoxic level starting from 2m to 10m depth at all stations Water conductivity and turbidity increases while pH decreased as depth increased The highest chlorophyll-a (1168 J-lgL) was recorded at 10m depth with positive correlation with turbidity Increasing levels of ammonia-nitrogen (00533 - 06400 mgL) total suspended solids (330 - 6306 mgL) and five-day biochemical oxygen demand (186 - 430 mgL) were observed while depth increases Nitrate (001 - 022 mgL) nitrite (00020 - 01170 mgL) silica (039 - 154 mgL) and orthophosphate (00900 - 17067 mgL) showed different variations with depth This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started

Keywords hydroelectric dam turbidity water quality nutrients

Abstrak

Sejak bekalan air di Empangan Hidroelektrik Bakun mencapai tahap penuh hanya satu kajian telah dijalankan semasa fasa pengisian iaitu 3 tahun dan 10 bulan lebih awal daripada kajian ini Disebabkan air di dalam empangan adalah sangat penting untuk organisma akuatik di dalam empangan dan bawah empangan satu kajian telah dijalankan di 3 stesen untuk mengenalpasti parameter kualiti air 5 tahun selepas penakungan bermula Di setiap stesen air telah diambil sebanyak tiga kali daripada 6 tahap iaitu subpermukaan 10m 20m 30m 40m dan 50m Hasil kajian menunjuk perbentukan termoklin pada kedalaman dari 3m ke 10m di semua stesen DO di subpermukaan (499shy610 mglL) menurun dengan drastik kepada tahap anoksik bermula pada kedalaman 2m ke 10m di semua stesen Konduktiviti air dan kekeruhan meningkat dan pH menurun dengan kedalaman Klorofil-a paling tinggi (1168 pgIL) adalah pada kedalaman 10m dan berkorelasi positijdengan kekeruhan air Peningkatan tahap ammonia-nitrogen (00533 shy06400 mgIL) jumlah pepejal terampai (330 - 6306 mgIL) dan keperluan oksigen biokimia selepas lima hari (186 - 430 mglL) meningkat apabila kedalaman meningkat Nitrat (001 - 022 mgIL) nitrit (00020 - 01170 mgIL) silika (039 - 154 mglL) dan ortofosfat (00900 - 17067 mglL) menunjukkan variasi yang berbeza dengan kedalaman Kajian ini menunjukkan bahawa kualiti air di Empangan Hidroelektrik Bakun bertambah baik dan masih berubah berbanding dengan kajian semasa fasa pengisian dan belum lagi staNI selepas 5 tahun dan 6 bulan sejak penakungan bermula

Kata kunci empangan hidroelektrik kekeruhan air kualiti air nutrien

III

Pusat Khidmat Maklumal Akadtmi UNIVEftSm MALAYSIA SAKAWA

TABLE OF CONTENTS

Declaration of Authorship

Acknowledgement

Abstract

Abstrak

Table of Contents

List of Figures

List of Tables

List of Abbreviations

10 Introduction

20 Literature Review

21 Reservoir

22 Water Quality

221 Temperature

222 Dissolved Oxygen (DO)

223 pH

224 Nutrients

23 Impact of Hydroelectric Dams on Water Quality

30 Materials and Methods

31 Study Site

32 Water Samples

33 Water Quality Parameters Measured In-situ

34 Water Quality Parameters Analysed Ex-situ

341 Biological Oxygen Demand (BODs)

342 Total Suspended Solids (TSS)

343 Chlorophyll-a

344 Ammonia-Nitrogen (NH3-N)

345 Nitrate (N03-)

346 Nitrite (N02-)

347 Orthophosphate (P043-)

348 Silica (Si04)

35 Statistical Analyses

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18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

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Figure

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LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

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20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

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Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

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EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 5: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Water Quality at Bakun HEP Reservoir Belaga Sarawak

Abstract

Since the water supply at Bakun Hydroelectric Dam reached its full supply level only one previous study has been done during the filling phase of the dam which was 3 years and 10 months earlier than this study As water in the reservoir is very important for the aquatic organisms in the reservoir and downstream of the dam a study was conducted at 3 stations to determine the selected water quality parameters 5 years 6 months after impoundment started At each station water in triplicate samples were collected at 6 levels which is the subsurface at 10m 20m 30m 40m and 50m depth Results showed that thermocline occurred at 3m to 10m depth at all stations DO at the subsurface (499 - 610 mgL) dropped drastically to anoxic level starting from 2m to 10m depth at all stations Water conductivity and turbidity increases while pH decreased as depth increased The highest chlorophyll-a (1168 J-lgL) was recorded at 10m depth with positive correlation with turbidity Increasing levels of ammonia-nitrogen (00533 - 06400 mgL) total suspended solids (330 - 6306 mgL) and five-day biochemical oxygen demand (186 - 430 mgL) were observed while depth increases Nitrate (001 - 022 mgL) nitrite (00020 - 01170 mgL) silica (039 - 154 mgL) and orthophosphate (00900 - 17067 mgL) showed different variations with depth This present study showed that the water quality at Bakun Hydroelectric Dam was improving and still changing compared to the previous study during the filling phase and has not stabilize even after 5 years 6 months after impoundment started

Keywords hydroelectric dam turbidity water quality nutrients

Abstrak

Sejak bekalan air di Empangan Hidroelektrik Bakun mencapai tahap penuh hanya satu kajian telah dijalankan semasa fasa pengisian iaitu 3 tahun dan 10 bulan lebih awal daripada kajian ini Disebabkan air di dalam empangan adalah sangat penting untuk organisma akuatik di dalam empangan dan bawah empangan satu kajian telah dijalankan di 3 stesen untuk mengenalpasti parameter kualiti air 5 tahun selepas penakungan bermula Di setiap stesen air telah diambil sebanyak tiga kali daripada 6 tahap iaitu subpermukaan 10m 20m 30m 40m dan 50m Hasil kajian menunjuk perbentukan termoklin pada kedalaman dari 3m ke 10m di semua stesen DO di subpermukaan (499shy610 mglL) menurun dengan drastik kepada tahap anoksik bermula pada kedalaman 2m ke 10m di semua stesen Konduktiviti air dan kekeruhan meningkat dan pH menurun dengan kedalaman Klorofil-a paling tinggi (1168 pgIL) adalah pada kedalaman 10m dan berkorelasi positijdengan kekeruhan air Peningkatan tahap ammonia-nitrogen (00533 shy06400 mgIL) jumlah pepejal terampai (330 - 6306 mgIL) dan keperluan oksigen biokimia selepas lima hari (186 - 430 mglL) meningkat apabila kedalaman meningkat Nitrat (001 - 022 mgIL) nitrit (00020 - 01170 mgIL) silika (039 - 154 mglL) dan ortofosfat (00900 - 17067 mglL) menunjukkan variasi yang berbeza dengan kedalaman Kajian ini menunjukkan bahawa kualiti air di Empangan Hidroelektrik Bakun bertambah baik dan masih berubah berbanding dengan kajian semasa fasa pengisian dan belum lagi staNI selepas 5 tahun dan 6 bulan sejak penakungan bermula

Kata kunci empangan hidroelektrik kekeruhan air kualiti air nutrien

III

Pusat Khidmat Maklumal Akadtmi UNIVEftSm MALAYSIA SAKAWA

TABLE OF CONTENTS

Declaration of Authorship

Acknowledgement

Abstract

Abstrak

Table of Contents

List of Figures

List of Tables

List of Abbreviations

10 Introduction

20 Literature Review

21 Reservoir

22 Water Quality

221 Temperature

222 Dissolved Oxygen (DO)

223 pH

224 Nutrients

23 Impact of Hydroelectric Dams on Water Quality

30 Materials and Methods

31 Study Site

32 Water Samples

33 Water Quality Parameters Measured In-situ

34 Water Quality Parameters Analysed Ex-situ

341 Biological Oxygen Demand (BODs)

342 Total Suspended Solids (TSS)

343 Chlorophyll-a

344 Ammonia-Nitrogen (NH3-N)

345 Nitrate (N03-)

346 Nitrite (N02-)

347 Orthophosphate (P043-)

348 Silica (Si04)

35 Statistical Analyses

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IV

18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

v

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Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

-

LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 6: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Pusat Khidmat Maklumal Akadtmi UNIVEftSm MALAYSIA SAKAWA

TABLE OF CONTENTS

Declaration of Authorship

Acknowledgement

Abstract

Abstrak

Table of Contents

List of Figures

List of Tables

List of Abbreviations

10 Introduction

20 Literature Review

21 Reservoir

22 Water Quality

221 Temperature

222 Dissolved Oxygen (DO)

223 pH

224 Nutrients

23 Impact of Hydroelectric Dams on Water Quality

30 Materials and Methods

31 Study Site

32 Water Samples

33 Water Quality Parameters Measured In-situ

34 Water Quality Parameters Analysed Ex-situ

341 Biological Oxygen Demand (BODs)

342 Total Suspended Solids (TSS)

343 Chlorophyll-a

344 Ammonia-Nitrogen (NH3-N)

345 Nitrate (N03-)

346 Nitrite (N02-)

347 Orthophosphate (P043-)

348 Silica (Si04)

35 Statistical Analyses

Page

I

II

III

III

IV

VI

VII

VIII

3

3

3

4

5

5

6

7

9

9

11

11

11

11

12

13

14

14

15

16

16

17

IV

18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

v

I

Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

-

LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 7: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

18 40 Results

41 Water Quality Parameters Measured In-situ 18

411 Water Depth and Transparency 18

412 Temperature 18

413 Ph 23

414 Water Turbidity 26

415 Water Conductivity 28

416 Dissolved Oxygen (DO) 31

42 Water Quality Parameters Measured Ex-situ 35

421 Chlorophyll-a 35

422 Biochemical Oxygen Demand in Five Days (BOD5) 37

423 Nitrate (NOf) 39

424 Nitrite (N02-) 42

425 Ammonia-Nitrogen (NH3-N) 44

426 Silica (Si04) 46

427 Orthophosphate (P043-) 48

428 Total Suspended Solids (TSS) 50

50 Discussion 52

51 Water Parameters Measured In-situ 52

52 Water Parameters Measured Ex-situ 57

60 Summary 63

70 Conclusion 65

80 References 66

90 Appendices 71

v

I

Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

-

LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 8: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

I

Figure

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

-

LIST OF FIGURES

Title Page

The location of sampling stations at Bakun Dam Sarawak 10

19

Temperature values in November 2015

Temperature values in August 2015

21

Temperature profile in August 2015 22

Temperature profile in November 2015 23

PH values in August 2015 24

PH values in November 2015 25

Turbidity values in August 2015 27

Turbidity values in November 2015 28

Water conductivity values in August 2015 29

Water conductivity values in November 2015 30

Dissolved oxygen (DO) values in August 2015 32

Dissolved oxygen (DO) values in November 2015 33

Dissolved oxygen (DO) profile in August 2015 34

Dissolved oxygen (DO) profile in November 2015 34

Chlorophyll-a values in August 2015 36

Chlorophyll-a values in November 2015 37

BODs values in August 2015 38

BODs values in November 2015 39

Nitrate-N values in August 2015 41

Nitrate-N values in November 2015 41

Nitrite-N values in August 2015 43

Nitrite-N values in November 2015 43

Ammonia-N values in August 2015 45

Ammonia-N values in November 2015 45

Silica values in August 2015 47

Silica values in November 2015 47

Orthophosphate values in August 2015 49

Orthophosphate values in November 2015 49

TSS values in August 2015 51

TSS values in November 2015 51

VI

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 9: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

LIST OF TABLES

Table Title Page

Table 1 Coordinates and locations of sampling stations 10

Table 2 Water depth and transparency values in August 2015 18

Table 3 Classification of water quality parameters according to NWQS 64

VII

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 10: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

LIST OF ABBREVIATIONS

degC Degree Celsius

lm Micrometre

BOD Biological Oxygen Demand

DO Dissolved Oxygen

km2 Kilometre Square

3m Cubic Metre

mgL Milligram per litre

mL Millilitre

L Litre

nm Nanometre

mm Millimetre

pH Potential of Hydrogen

N Nitrogen

N02- Nitrite

N03- Nitrate

P04 3- Orthophosphate

Si04 Silica

NH3-N Ammonia-Nitrogen

TSS Total Suspended Solids

TDS Total Dissolved Solids

GPS Global Positioning System

VIII

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 11: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

10 Introduction

Hydroelectric dams have been constructed worldwide to provide an alternative

energy source as petroleum in the world is depleting and is not renewable Hence

impoundment started around the world to collect water bodies to act as a reservoir

Reservoirs formed by impoundment they will undergo great changes in water

quality (Chapman 1996) This was observed in tropical reservoirs such as Feitsui

Reservoir in Taiwan (Chang and Wen 1997) and Lake Brokopondo in Surinam (Van der

Heide 1978) and also temperate reservoirs such as Butgenbuch Reservoir in Belgium

(Lourantou et aI 2007) and Bureye Reservoir in Russia (Shesterkin 2008) This happens

because of the impact of inundated soil and vegetation including the standing forest on the

water quality such as pH level and dissolved oxygen concentration (Van der Heide 1978

Shesterkin 2008) which is essential for aquatic life

In Malaysia hydroelectric dams have been constructed to meet the energy needs

and security Among the hydroelectric dams that have been built in Sarawak is the Bakun

Hydroelectric Dam Construction of the dam started in 2002 It is located about sixty

kilometers from the town of Belaga and is situated on the Balui River Bakun

Hydroelectric Dam is the largest hydropower project in Malaysia that can produce up to

2400 MW of electricity (httpwwwsarawakenergycomrny)Itis the second highest

concrete faced rockfill dam in the world with an area of 695 square kilometers and a height

of 207 meters (httpwwwsarawakenergycomrny) Research on the characteristics of

physico-chemical water quality at Bakun Dam has been conducted by Nyanti (2012)

However it was conducted during the filling phase of the hydroelectric dam which is

fifteen months after impoundment has started Since then there has been no publishing

literature on the characteristics of the water quality

1

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 12: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Hence the goal of this study is to obtain detailed information on the physicoshy

chemical water properties of the Bakun Hydroelectric Dam 3 years and 7 months after it

has reached its full supply level Therefore the objectives of this study were

(i) To determine the water quality at six depths at three stations in the

reservOIr

(ii) Compare the characteristics of the water quality among the depths and

stations and

(iii) Determine the changes in water quality characteristics 5 years 6 months

after the dam was impounded

2

jl - - I

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 13: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

20 Literature Review

21 Reservoir

According to Pawar amp Shembekar (2012) water is important and it is the most

abundant resource in the world which man has used for decades Water covers about 70

of the earths surface but only 27 of the total amount is freshwater of which 1 is iceshy

free water in the rivers lakes and atmosphere as biological water It is believed that only

0001 92 of the total water on earth is available for human use (Pawar amp Shembekar

2012) Hence reservoirs are created in order to provide domestic water supply generation

of electricity and aquaculture In Malaysia 63 large reservoirs with a total storage of 25

billion m3 have been constructed (Makhlough 2008)

Water quality in reservoirs is greatly affected by the composition of plant materials

that were submerged during the inundation process In a study done by Ling (2012) water

in the Batang Ai reservoir contains high sulfide concentrations especially at inundated

areas Besides that Nyanti (2012) also reported that the anoxic condition and the acidic

condition in Bakun Dam is due to the decomposition of submerged carbonaceous

materials

Additionally human activities in and around reservoirs and the physical and

chemical properties of water will be affected (Mustapha 2008) Precipitation evaporation

and ground movement can also affect water quality In Batang Ai reservoir the dissolved

oxygen was reported to be lower due to nearby cage aquaculture as it is consumed by

microorganisms in the decomposition of organic matter (Ling 2012)

22 Water quality

Water quality in a reservoir is the physical and chemical limnology of a reservoir

(Sidnei 1992) and includes all physical chemical and biological aspects of water that

3

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 14: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

influence the beneficial usage of water (Mustapha 2008) In reservoirs water quality

deterioration usually comes from excessive nutrient inputs eutrophication acidification

heavy metal contamination organic pollution and obnoxious fishing practices (Mustapha

2008)

Therefore water quality is an important indicator of the ecological status of a

reservoir It is reported that the significant lower dissolved oxygen is recorded due to

higher turbidity and increased suspended solids which affect the dissolution of oxygen

which is brought in by the flood that occurred in Oyun Reservoir (Mustapha 2008)

Additionally in a study done at Bakun Dam turbidity is affected by the suspended solids

from eroded soils from the logging activities in the watershed upstream from the north of

the reservoir (Nyanti 2012)

221 Temperature

Temperature is very important to a reservoir as it affects chemical and biological

activities of aquatic organisms (Sangpal 2011) In a reservoir when the upper layer and

the lower layer have great variation in temperature thermocline will occur Thermal

stratification in deep reservoir is an important natural process which gives significant

effects on water quality The production of ammonia sulphide and algal nutrients are

dependent on the changes in water temperature which subsequently affects the water

quality (Baharim 2011) Besides that vertical distribution and change in water

temperature can affect productivity of the natural organisms in the reservoirs However

the effect varies from reservoir to reservoir According to Li amp Xu (1995) thermocline is

common in reservoirs and usually occurs at the depth of 8m to 23m In a study done by

Nyanti (2012) water temperature in Bakun reservoir was reported to undergo thermocline

as depth increased from subsurface to 18m

4

l I

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 15: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Pusat Khidmat Maldumat Akadfmil UN nsmMALAYSIA SARAWAI~

222 Dissolved Oxygen (DO)

DO is a very essential environmental factor that affects the entire production of a

reservoir and it is also an important indicator of water quality health of reservoir and also

ecological status as it is used for respiration and in biological and chemical reactions

(Mustapha 2008)

DO fluctuate from reservOIr to reservOIr and it is usually affected by

photosynthesis respiration and diel fluctuation In a study done by Ling (2012) it was

reported that the DO is higher at 05m depth at a11 stations in Batang Ai reservoir ranging

from 47 to 87 mgL due to the high phytoplankton photosynthesis rate An example of

diel fluctuation is shown in Kontagora reservoir where the DO is higher during the dry

season than the rainy season (Ibrahim 2009) This shows that the fluctuation also depends

on temperature depth wind and amount of biological activities such as decomposition In

Bakon Dam DO is high at the subsurface but dropped drastically until anoxic level at

depth 2 - 4m 2 years after impoundment and this is mainly due to the decomposition of

organic matter (Nyanti 2012)

223 pH

pH that is suitable for optimal production for inland waters should be about 65 to

85 (Ibrahim 2009) However changes in pH can affect the transfer of nutrients and affect

the condition ofwater quality (Li amp Xu 1995)

Fluctuations in pH can be caused by the photosynthesis process of phytoplanktons

as was reported in Batang Ai reservoir where all pH value was above 7 (Ling 2012)

Carbon dioxide produced by photosynthesis process will alter the pH of water as carbonic

acid will be formed when carbon dioxide reacts with water (Sangpal 2011)

5

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 16: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Acidic effects in reservoirs can be caused by the transfer of cooler water from other

tributaries where the water is denser and lower in pH Nyanti (2012) reported the pH value

at Bakundam were all acidic ranging from 517-592 and the overall trend of pH in Bakun

dam decreases from upstream towards the dam (Nyanti et aI 2012)

224 Nutrients

Reservoirs are often have higher chances of getting higher element loading

compared to natural lakes as they have greater catchment area and high inflow rates

(Pawar amp Shembekar 2012) The concentration of nutrients varies from reservoir to

reservoir due to the differences in soil and vegetation in the catchment area (Li amp Xu

1995) Nutrients such as nitrates phosphates silicates and iron are important nutrients

required for aquatic growth but may also cause eutrophication and water quality problems

(Li amp Xu 1995) Eutrophication can occur easily in reservoir due to high input of nutrients

into the water and water quality of reservoir will be affected giving rise to unpleasant taste

and odour and affects the dissolution of other gases especially dissolved oxygen

(Mustapha 2008) According to Nyanti (2012) strong rotten egg smell discovered in

Bakun dam indicates high volume of hydrogen sulfide This observation is also supported

by Lourantou (2007) where an irritating odour smell occurs at a reservoir in Belgium

Nutrients input can also be affected by weather and season where nitrate was recorded at

higher values in Ujjani reservoir during post-monsoon season This may be caused by the

oxidation of nitrifying bacteria and biological nitrification Sulphate concentrations in the

dam were very high in both pre and post-monsoon which were probably caused by the

mineral rocks anthropogenically added and also by rain (Sangpal 2011) The phosphate

levels were found to be lower during the pre-monsoon and higher during the postshy

6

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 17: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

monsoon Phosphate leads to eutrophication that can cause unpleasant taste and odour to

the water (Sangpal 2011)

23 Impacts of hydroelectric dams on water quality

Hydroelectric dam has a direct impact to the water quality as it uses the flow rate of

a water course to produce electricity The building of hydroelectric dams has direct impact

towards the chemical thermal and physical parameters of the water body (Bunea 2012)

According to a study done by Bunea (2012) hydroelectric dams have relatively low DO

concentration mostly lower than 50 mglL because of the organic sediments that are left at

the bottom of the reservoir bottom during the initial filing Organic substances left at the

bottom of the reservoir bottom floor will absorb oxygen from the water in order to

decompose producing hydrogen sulphide carbon dioxide and methane (Bunea 2012)

Due to damming for hydroelectric generation water in a reservoir will undergo

stagnation which will lead to thermal stratification (Bunea 2012) According to a study

done by Elci (2008) thermal stratification of the reservoir involves the higher temperature

at the surface and lower temperatures at the bottom which suggests that thermal energy is

very slowly transferred to the bottom layers of the water body Thermal stratification act as

a barrier to re train mixing of the water column This causes an uneven concentration of

nutrients lack of light for photosynthesis at the hypolimnion and the water column may

become anoxic (Elci 2008)

Hydroelectric dams also greatly reduces the water self-purification capacity

According to Wei et al (2009) water self-purification mechanisms are affected by the

physical chemical and biotic processes in a reservoir However dam construction affects

all of the processes as the flow regime water quality and biotic community in the river In

other words dams slow down the river flow capacity block the river continuum and raise

7

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 18: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

water temperature which decreases the water self-purification capacity (Wei et aI 2009)

In a study done in China by Wei et al (2009) it is recorded that the Manwan-Dachaosan

dam has higher ammonia-nitrogen concentration due to the decreased water selfshy

purification capacity as compared to the pre-dam period This suggests that damming has

severely decreased the water self-purification capacity as it blocked the river continuum

8

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 19: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

30 Materials and Methods

31 Study Site

Bakun Hydroelectric Reservoir is a man-made reservoir which is located 60 km

west of Belaga Sarawak Malaysia (Figure 1) The dam was formed after the

impoundment of Balui River The reservoir has a catchment area of 14750 km2 and a total

capacity 43800000 m3 with a surface area of 695 km2 The dam is the second tallest

concrete-faced rockfill dam in the world

Three sampling stations namely stations 1 2 and 3 was selected in the reservoir

Station 1 is at the inundated estuary of the Linau River Station 2 is at the inundated Balui

River and Station 3 is located in the inundated Balui River as well but nearer to the dam

At each station sampling was conducted at 6 levels namely the subsurface 10m 20m

30m 4Om and 50m depths The coordinates of Bakun dam is at longitude 02deg45 23N and

latitude 114deg0347E The coordinates of every sampling station were recorded by the

Global Positioning System (GARMIN GPSMAP 62S) (Table 1) Sampling was carried

out twice the first sampling was from 21 SI August to 27th August 2015 and the second

sampling was 5th November to 11 th November 2015

9

i

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 20: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

EAST MALAYSIA

o

I

-I River I

-I Flooded Area

Station

0 Dam

kill I

Figure 1 Location of the three sampling stations at Bakun Reservoir

Table 1 Coordinates and locations of sampling stations

Station Coordinates Location

N 02deg 39 322 E 114deg 03 295 Estuary of Linau River

2 N 02deg 43 344 E 114deg 01 442 Balui River

3 N 02deg 43 4135 E 114deg 03 340 Further downstream of Balui River

10

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 21: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

32 Water samples

The water samples were taken using Van Dorn water sampler at all three stations

and were taken at 6 different depths which are the subsurface (02m) 10m 20m 30m 40m

and 5Om At each station three replicates of water samples were taken back for laboratory

analysis Water samples were kept in 2 L polyethylene water bottles that has been acid

washed and were stored in cooler box filled with ice All samples were taken to the

laboratory for further analysis

33 Water quality parameters measured in-situ

Temperature dissolved oxygen (DO) pH electrical conductivity total dissolved

solids (TDS) and turbidity were taken using YSI Multiparameter Water Quality 6920 V2

The depths of each station were measured using depth finder Water transparency was also

measured using secchi disc at each station

34 Water quality parameters analysed ex-situ

341 Biochemical oxygen demand in five days (BODs)

BODs were determined by filling water samples into 300 ml BOD bottles DO

readings of the water samples were measured from the bottles All BOD bottles were

wrapped with aluminum foil to prevent light penetration and were kept in a cooler box for

5 days The initial DO value was recorded as DJ and on the 5th day the DO reading was

recorded as Ds The formula that was used for measuring BODs follows the protocol

outlined by APHA (1998)

11

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 22: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

BOD5 (mglL) = DJ - D5

Where DJ = Initial DO of sample immediately after preparation (mglL)

D5 = DO value after 5 days incubation at 25degC (mglL)

342 Total suspended solids (TSS)

Total suspended solids were analyzed using standard method APHA (1998) For

TSS analysis there was pre-fieldtrip sampling method and post-fieldtrip method For preshy

fieldtrip method glass fibre filter paper (GFIC 47 nun diameter 045 Ilm membrane) were

soaked in distilled water Each filter paper is placed on a piece of aluminum foil and was

dried in the oven at 103degC - 105degC overnight Filter paper then was allowed to cool for 10

minutes before weighing it using an analytical balance (ACCULAB ALC - 210) The

initial weight was recorded For post-fieldtrip method the glass fibre paper was placed on

the inter-plate of the filter funnel using a pair of forceps A known volume of water

samples was filtered using a vacuum pump After that filter paper was removed from the

filtration funnel and was placed back into the aluminum foil Filter paper was dried in the

oven at 103degC - 105degC overnight (APHA 1998) Filter paper was then taken out of the

oven and allowed to cool until room temperature before weighing The final reading of the

filtered glass fibre paper was recorded and TSS was calculated using the formula

w -wTSS (mglL) = J I

V

Where W = Initial weight of filter paper

WJ = Final weight of filter paper

V = Volume of water samples filtered (L)

12

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 23: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

4 Chlorophyll-a

The concentration of chlorophyll-a In the water samples were analyzed using

staDdard method APHA (1998) For chlorophyll-a analysis water samples were filtered

using vacuum pump Filter paper containing chlorophyll-a was taken from the vacuum

pump for analysis The samples were grinded by using a grinder and 5 - 6 mL of 90

acetone was added into the mortar Samples were grinded for about 5 minutes and all

materials in the mortar were placed into a capped test tube Ninety percent acetone was

added into the test tube to make up the volume to 10mL Test tube was folded with

aluminum foil and was placed in the refrigerator for 4 - 18 hours to facilitate complete

extraction of the pigments The liquid extracted was transferred into the centrifuge tube

The samples were placed into a centrifuge for about 10 minutes under 3000 rpm Optical

density was determined using spectrophotometer at wavelength of 750 nm 664 run 647

am and 630 nm Each extinctions for small turbidity blank was corrected by subtracting

750 nm from 664 nm and 630 run absorptions

The concentration of chlorophyll-a in the extract of the pigment after correction was

calculated using

Where E = the absorption in the respective wavelength

After determining the concentration of the chlorophyll-a in the extract the amount of

cblorophyll-a in the pigment per unit volume of water filtered was calculated as follows

13

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14

Page 24: Water Quality at Bakun HEP Reservoir, Belaga, Sarawak quality at Bakun HEP reservior... · Water Quality at Bakun HEP Reservoir, Belaga, Sarawak WiUieKoh (44620) ... Water Quality

Ca(v)Chlorophyll-a (Jg IL) = - shyv

Where Co = Chlorophyll-a pigment concentration in JgmL

v = Volume ofacetone in mL

v = Volume of samples in L

344 Ammonia-nitrogen (NH3-N)

For ammonia-nitrogen (NH3-N) the concentration was determined using standard

method 8038 Nessler Method (HACH 2000) A 25 mL prepared sample and 25 mL of

deionized water were filled into a separate 25 mL mixing graduated cylinder Three drops

of Mineral Stabilizer were added to both of the cylinders The cylinders were inverted

several times to mix the content After that 1 mL of Nessler reagent was pipetted into both

of the cylinders and the cylinders were inverted several times to mix the content A one-

minute reaction was started Both the solutions were poured into a square sample cell A

yellow colour formation will indicate the presence of ammonia When the timer expired

the blank was inserted into the square sample cell with the fill line facing the right The

reading at 425 run was zeroed The prepared sample was inserted into the cell holder of

Spectrophotometer DR 2800 (HACH 2000) with the fill line facing right and the reading

displayed was recorded

345 Nitrate (NO)-)

For nitrate analysis the concentration was determined using standard method 8192

Cadmium Reduction Method (HACH 2000) The sample was filled until the 15 mL mark

of a 25 mL graduated measuring cylinder The content of one Nitra Ver6 Nitrate Reagent

Pillow Powder was added into the cylinder and capped with a stopper The cylinder was

14