RESERVE DETERMINATION OF PRIORITY WATER RESOURCES IN …€¦ · The natural, present day and seven...

Information Brochure 2 August 2015

RESERVE DETERMINATION OF PRIORITY WATER RESOURCES IN THE USUTU, PONGOLA, LAKE SIBAYI, MKUZE, MFOLOZI AND MHLATUZE CATCHMENTS

BACKGROUND INFORMATION DOCUMENT

Aim of this Document

This Background Information Document (BID) is to inform water users and other stakeholders in the Usutu Mhlatuze Water Management Area (WMA) of the Reserve Determination studies that are being done for selected surface and groundwater resources in the Usutu Mhlatuze WMA

Stakeholders are invited to raise issues and concerns about the project to ensure that all relevant issues are investigated and included in the Reserve Determination process. Your comments will be considered during the study process and submitted to the Department of Water and Sanitation (DWS).

Please direct comments to: Adhishri Singh, Tlou Consulting (Pty) Ltd

Tel. (012) 336 9800, Email: [email protected]

INTRODUCTION

The National Water Act of 1998 (Act No. 36 of 1998) (NWA) (Chapter 3, Part 3) provides for the protection of significant water resources by means of the Reserve. As the custodian of the nation’s water resources, DWS has the responsibility to ensure the adequate protection, the effective management and the sustainable utilisation of these resources. The Chief Directorate: Water Ecosystems within the DWS is tasked with ensuring that Reserve Requirements, which take priority over other uses in terms of the NWA, are determined before licensing applications can be processed, particularly in water-stressed catchments.

DWS appointed Tlou Consulting (Pty) Ltd to manage and coordinate the Usutu Mhlatuze Reserve Determination Study (UMRDS). They are supported by a number of specialist subcontractors to provide technical inputs for the Reserve determination studies.

The study is funded by the Water Ecosystems Chief Directorate of DWS.

The Usutu Mhlatuze WMA is situated in the northern portion of KwaZulu-Natal Province where it borders Swaziland and Mozambique. The Usutu and Pongola Rivers are shared with these countries. It comprises a number of surface-water basins: Mhlatuze, Mfolozi, Mkuze, Pongola, Upper Usutu and Lake Sibaya and Kosi (Figure 1).

Figure 1. Map of Usutu Mhlatuze WMA, showing basin boundaries

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BACKGROUND The study was necessitated by the high conservation status and importance of several water-resources in the basin and the significant development pressures in the area, which are likely to impact on both the availability of water and the condition of the ecosystems that provide it.

There are a number of important conservation areas in the WMA, including the priority Isimangaliso wetland complex (St Lucia and Kosi Bay) complex, a World Heritage Site. Competing water demands in the WMA include forestry, irrigation and industrial users (such as water intensive industries in Richards Bay). In addition, the need to supply domestic water to largely rural populations place additional requirements on the available water resources.

Reserve determinations are therefore required to assist the DWS to make informed decisions on the authorisation of future water use.

• the Pongola floodplain; St Lucia/Mfolozi Estuary; and Lake Sibaya at an intermediate level of detail; and

• the Amatikulu Estuary, Mlalazi Estuary, and Kosi Lake and Estuary at a rapid level of detail.

Additional specific tasks include: • classifying the causal links between water

supply and condition of key wetlands; • include results of EWR assessments of

Mhlatuze (river and estuary) and Nhlabane (lake and estuary);

• determine groundwater contributions; • determine Basic Human Needs Reserve for

the catchment and socioeconomic needs; and

• build stakeholder capacity in EWR and reserve determinations.

The Reserve determination study is following the 8 step process outlined in the National Water Act (1998) and its subsequent refinements including ecoclassification (2007) and water resource classification system amendments (2008), as summarised in Figure 2.

STUDY SCOPE AND PROCESS


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The study scope included determination of the Ecological Reserve for:

• the Nyoni, Matigulu, Mlalazi, Mhlatuze, Mfolozi, Nyalazi, Hluhluwe, Mzinene, Mkuze, Assegaai and Pongola Rivers at various levels of detail;

Preliminary*implementation*action*plan

Initiate*and*define*study*area

Decide*on*Reserve*components*(groundwater,*estuaries,*rivers)

Define*Resource*Units

Select*EWR*Sites

Ecoclassification

Set*objectives*of*each*EC*and*establish*REC

Quantify*EWR*requirements

Define*operational*scenarios

Model*impact*of*EWR*on*

availability

Determine*ecological*

consequences

Determine*social*

consequences

Define*ecological*monitoring*protocol

Define*Ecospecsand*TPCs*for*REC

1.*DEFINE*STUDY 2.*RESOURCE*UNITS

3.*ECOLOGICAL*CLASSIFICATION

DWA*decision*on*operational*scenarios

6.*DECISION*MAKING

4.*EWR*QUANTIFICATION

5.*OPERATIONAL*SCENARIOS*AND*CONSEQUENCES

8.*IMPLEMENTATION*PLAN 7.*ECOSPECS*AND*MONITORING

Figure 2. DWS 8-step process for Ecological Reserve Determination

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August 2015 Information Brochure 2

The study tasks and status of work completion is summarized in Table 1.

Table 1. Record of Work completion

Task Status 1 Project Management Ongoing 2 Project Inception Complete 3 Hydrology Partial 4 Intermediate river EWRs Complete 5 Rapid river EWRs Complete 6 Pongola floodplain Intermediate EWR Complete 7 Wetlands and groundwater Partial

8 St Lucia/Mfolozi Estuarine System Intermediate EWR

Partial

9 Mlalazi Estuary Rapid EWR Complete 10 Amatikulu Estuary Rapid EWR Complete 11 Kosi Estuary Rapid EWR Partial 12 Mhlatuze, Nhlabane and other existing

estuary review EWRs Complete

13 Lake Sibaya Intermediate EWR Partial 14 Socio-economic profile of the WMA Complete 15 Basic Human Needs Reserve Partial 16 Study Closure -

STUDY TASKS INTERMEDIATE EWRS FOR RIVERS

Step 1: Define Study Area & Reserve Components

The inception phase of the study confirmed the study area and the reserve components, as summarised in Table 1.

Step 2: Define Resource Units and Select EWR sites

This step involved:

• Delineation of river reaches based on the National Water Resource Classification System (NWRCS) methods, which resulted in 49 river nodes, plus 104 507 ha of wetlands and 9 estuaries.

• Selection of eight Intermediate EWR sites, representing seven river groupings: Assegaai (1); Upper Pongola (1); Black Mfolozi (2), White Mfolozi (1), Mkuze (1), Nseleni (1) and Matigulu Rivers (1), from a shortlist of 30 potential locations selected in ten rivers. These sites are shown in Figure 3.

Matigulu River

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Figure 3. Location of Intermediate River EWR Sites and nodes

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Step 3: Ecological Classification

This step involves two key activities: i) Ecoclassification of each EWR site (i.e. the categorisation of Present Ecological Status (PES) and Ecological Importance and Sensitivity (EIS) of the ecosystems, based on various biophysical attributes relative to the natural and/or reference condition), and ii) using these to identify Recommended Ecological Category (REC) for each.

PES and RECs for each site are summarised in Table 2.

Table 2: RECs for the intermediate river sites

River Site PES REC AEC1 AEC2 Assegaai AS1 C C B D Upper Pongola UP1 C C B D Mkuse MK1 C C B D Black Mfolozi BM1 C C B D Black Mfolozi BM2 C C B D White Mfolozi WM1 B/C B/C B C Nseleni NS1 C C B D Matigulu MA1 B/C B/C B C

Steps 4-7: Quantify EWR Scenarios; Operational Scenarios

DRIFT was used to assess the EWR and operational scenarios.

Table 3: EWRs for the REC at each intermediate river sites (in MCM)

River Site Maint. Lowflow

High Flows

MAR

Assegaai AS1 69.287 23.363 278.073 Upper Pongola UP1 102.922 45.272 288.704 Mkuze MK1 61.948 60.736 275.487 Black Mfolozi BM1 2.910 6.658 31.784 Black Mfolozi BM2 12.570 16.381 96.141 White Mfolozi WM1 76.663 74.255 300.210 Nseleni NS1 11.242 3.577 32.111 Matigulu MA1 22.037 14.767 85.236

Steps 8: Ecospecs

Ecospecs and Thresholds of Potential Concern for the REC have been identified for Hydrology, Water Quality, Geomorphology, Vegetation, Macroinvertebrates and Fish.

Step 1: Define Study Area & Reserve Components

The inception phase of the study confirmed the study area and the reserve components, as summarised in Table 1.

Step 2: Define Resource Units and Select EWR sites

This step involved:

• Identification of the pans on the Pongola Floodplain.

• Selection of 11 pans for Intermediate EWR assessment. These sites are shown in Figure 4.


INTERMEDIATE EWR FOR PONGOLA FLOODPLAIN

Figure 4. Location of Pongola Floodplain Pans

Mfolozi River

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PES and RECs for the study pans are summarised in Table 4.

Table 4: RECs for the Pongola Floodplain pans

Pan PES REC AEC1 Ntlanyane E/F D/E D/E Mzinyeni D/E C/D D Mthikeni D/E C/D D Tete D/E C/D D Khangazini D/E C/D D Shalala D/E D D Sokunti D/E C D Namanini D/E C/D D Mandlankuzi D/E C/D D Nyamithi D/E B/C D Bakabaka D/E B D

Ecological importance and sensitivity (EIS) were assessed using the draft rapid Reserve approach as a reflection of its role in maintaining ecological diversity and functioning on local and wider scales; and the system’s ability to resist or recover from disturbance, respectively.

Despite PES scores reflecting a modified to largely modified ecosystem (Table 4 above), the EIS assessment indicates that the floodplain system falls within a Very High category because of the range of ecosystem services provided by the floodplain and its pans. The Pongola floodplain is thus considered ecologically important and sensitive on a national or even international level. The biodiversity of wetland systems falling within this category are usually very sensitive to flow and systems modifications. The floodplain is also expected to play a major role in moderating the quantity and quality of water of the Pongola River.

Steps 4-7: Quantify EWR Scenarios; Operational Scenarios

A 2-D, depth-averaged, hydrodynamic model using finite elements, known as RMA, was developed for the entire floodplain.

The EWR assessment focussed on evaluation of the predicted impact on the social and ecological attributes of the floodplain, with consideration of the volume of water required from Jozini Dam. The natural, present day and seven EWR release scenarios were evaluated as summarised in Table 5.

Table 5: Scenarios evaluated for the Pongola Floodplain

# Scenario name Code MAR (MCM)

1 Baseline: 2014 release operations

Base 579.94 2 Naturalised Nat 1121.67

3 Base but with ‘October’ flood in September

Base_Sept 580.68

4 Heeg and Breen (1982) – adjusted to = 250 MCM/a HB_250 588.28

5 HB_250 with the December flood in October

HB_mod 588.85

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Base, with October flood at 600 m3s-1, PLUS December and February floods from Heeg and Breen (1982)

HB_R600 582.82

7 HB_R600 but flood at 400 m3s-1

HB_R400 593.79

8 HB_mod –plus future demands (2040)

HB_modD1

561.16

9 HB_modD1 with water demand management

HB_modD2

581.10

Note: Baseline dam releases are designed to fill the pans in Ndumo Game Reserve, but do not necessarily achieve this target, mainly because the October release does not coincide with the flooding season in the Usuthu River.

The two scenarios that yielded the best overall ecosystem and social outcomes overall are HB_mod and HB_600. Figure 5 shows that HB_mod, HB_600 and HB_modD2 approximate the natural scenario, while HB_400 and HB_modD1 are not significantly lower than the top scoring three scenarios. Scenario HB_600 has the best social outcomes overall (Figure 6).


Nyamithi Pan in Ndumo Game Reserve

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Figure 5: Overall ecosystem integrity scores for

whole floodplain for all scenarios

Figure 6: Overall social well-being scores for

whole floodplain for all scenarios

Scenario HB_600 represents the best outcome for both the ecosystem and social aspects from the range of scenarios evaluated.

Table 6 Translation of Scenario HB_600 into releases from Jozini Dam

Month Release Schedule

October One day at 600 m3s-1 Remaining days at 2.4 m3s-1

December

Three days at 150 m3s-1 Remaining days at 2.4 m3s-1. Two days at 56 m3s-1 Four days at 28 m3s-1 Remaining days at 2.4 m3s-1.

January Two days at 50 m3s-1. One day at 35 m3s-1; followed by one day at 65 m3s-1. Repeat three times. Remaining days at 2.4 m3s-1.

February Five days at 150 m3s-1. Remaining days at 50 m3s-1.

The HB_600 release scenario is predicted to yield a better overall outcome for the ecosystem and its users than the baseline (2014) scenario 9 (Figure 7). However, further optimisation is possible based on analysis of further release scenarios for Jozini Dam, and adaptive management based on monitoring. The tool to undertake this analysis has been developed under this study.

Figure 7. Comparison of Estimated Ecological Condition for Baseline 2014 Condition and Scenario HB_600

Steps 8: Ecospecs

Not done.

RAPID EWR FOR THE MLALAZI ESTUARY

Step 1 and 2: Define Study Area, Select Resource Units and EWR sites

The mouth of the Mlalazi Estuary is approximately 105 km north east of Durban and 56 km south of Richards Bay. For the purposes of this EWR study, the geographical boundaries of the estuary were defined as shown in Figure 8.

The Mlalazi Estuary is a “temporarily open/closed estuary”, with mouth closure for about 4% of the time.

KEYABB/CC

C/DDD/EEF

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The Present Ecological State of the Mlalazi Estuary is a B Category, estimated to be 80% similar to the Natural condition. The overall current Estuarine Health Score as well as the score with non-flow related pressures removed is given in Table 7 below.

Table 7. Estuarine Health Score for the Mlalazi Estuary

Variable

Estuarine health score

Overall Excluding non-flow related pressures

Estuary Health Score 80 88

Present Ecological Status (PES) B A/B

Estuarine Importance

Estuary Importance was rated at 85, indicating that the estuary is rated as “Highly Important”.

Table 8. Description of flow scenarios

Scenarios Description MAR % RemaiReference Natural Flow 164.31 100

Present Present day 124.57 76

Scenario 1 Present day plus 13 Mm3

additional demand 112.46 68

Scenario 2 Present day reduced by 10% through abstraction from lower reaches of river

111.89 68

Scenario 3 Present day reduced by 20% through abstraction from lower reaches of the river

102.93 63

Scenario 4

Scenario 3 plus additional demand of 10% MAR is taken out the upstream catchment from a dam 86.74 53

The individual Estuarine Health Index (EHI) scores, as well as the corresponding ecological category under different scenarios are provided in the Table 9 below.

Table 9. EHI score and corresponding Ecological Categories under the different runoff scenarios

Pr

esen

t

Scen

ario

1

Scen

ario

2

Scen

ario

3

Scen

ario

4

Estuary Health Score 80 76 64 56 49

Ecological Category B B C D D

The flow requirement meet the recommended ecological category are the same as Present State, but with a 10 to 20% increase in baseflows. The increase in baseflows are to ensure an open mouth state.

Step 8: Ecological Specifications

Ecological specifications for the Present ecological State and the Recommended Ecological Category A/B have been set for the Hydrology, Hydrodynamics, Water Quality, Sediment Dynamics, Microalgae, Macrophytes, Invertebrates, Fish and Birds.

Figure 8. Geographical boundaries of the Mlalazi Estuary based on the Estuary Functional Zone

Based on this study, the National Biodiversity Plan targets and the reversibility of current impacts, the Recommended Ecological Category for the Mlalazi Estuary is an A/B Category

Step 4 – 7: Quantification of EWR Scenarios and Operational Scenarios

The EWR assessment focussed on evaluation of a range of development scenarios that could affect the Mlalazi estuary. The scenarios evaluated are provided in Table 8.


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Step 1 and 2: Define Study Area, Select Resource Units and EWR sites

The mouth of the Amatikulu-Nyoni Estuary is approximately 100 km north east of Durban and 56 km south of Richards Bay. The system comprises two separate estuaries, the Amatikulu and the Nyoni that are at times joined and at times separated. The separation of these two estuaries appears to be driven by extreme flood events. The combined estuary mouth closes from time to time, i.e. it is a “temporarily open/closed” estuary.

The current Rapid EWR Assessment is based on a situation where the two systems are joined.

For the purposes of this EWR study, the geographical boundaries of the estuary were defined as shown in Figure 9.

RAPID EWR FOR THE AMATIKULU/NYONI ESTUARY

Figure 9. Geographical boundary of the Amatikulu-Nyoni Estuary based on the Estuary Functional Zone


The Present Ecological State of the Amatikulu-Nyoni Estuary is a B Category, estimated to be 84% similar to the Natural condition. The overall current Estuarine Health Score as well as the score with non-flow related pressures removed is given in Table 10 below.

Estuarine Importance

The Estuary Importance was rated at 76, indicating that the estuary is “Important”.

Table 10. Estuarine Health Score for the Amatikulu-Nyoni Estuary

Variable

Estuarine health score

Overall Excluding non-flow related pressures

Estuary Health Score 84 89

Present Ecological Status (PES) B A/B

Taking into account, the current conditions (PES = B), the reversibility of some impacts, the ecological importance and the national conservation targets, the Recommended Ecological Category for the Amatikulu-Nyoni Estuary is an A/B Category.

Step 4 – 7: Quantification of EWR Scenarios and Operational Scenarios

The EWR assessment focussed on evaluation of a range of development scenarios that could affect the Amatikulu-Nyoni estuary. The scenarios evaluated are provided in Table 11.

Table 11. Description of flow scenarios

Scenarios Description MAR ( X106 m3)

% Remaining

Reference Natural Flow 192.27 100 Present Present 178.03 93

Scenario 1

Present + additional 10% reduction in MAR (baseflow abstraction) 160.73 84

Scenario 2 Present + additional 20% reduction in MAR (baseflow abstraction) 146.50 76

Scenario 3 Present + An additional 30% reduction in MAR (with dam) 126.87 66


Lower reaches of Nyoni Estuary

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The individual Estuarine Health Index (EHI) scores, as well as the corresponding ecological category under different scenarios are provided in the Table 12 below.

Table 12. EHI score and corresponding Ecological Categories under the different runoff scenarios

Pre

sent

Sce

nario

1

Sce

nario

2

Sce

nario

3

Estuary Health Score 84 72 64 56

Ecological Category B C C D

None of the scenarios achieved the REC of an A/B Category. Therefore the Present Ecological State in conjunction with a number of management interventions is the recommended ecological flow scenario.

Step 8: Ecological Specifications

Ecological specifications for the Present ecological State and the Recommended Ecological Category A/B have been set for the Hydrology, Hydrodynamics, Water Quality, Sediment Dynamics, Microalgae, Macrophytes, Invertebrates, Fish and Birds.

Economic Issues related to extended Mouth Closure

Increased closure will have an impact on the offshore Thukela Banks prawn fishery, which has currently collapsed due to the extended mouth closure of the St Lucia System. There has also been a knock on effect in the fish populations where it has been found that offshore breeding stocks of Rhabdosargus sarba have declined drastically and aged due to the loss of estuarine nursery facilities (Mann & Pradarvand, 2007). Extended closures of other important estuaries, which have an important nursery function, such as Amatikulu-Nyoni, could further impact on the declining stocks.

Increased closure of the mouth also has economic implications due to the fact that some rural ‘block’ sugar farming is taking place on the flood plain within the 5m a.m.s.l. contour. This will result in pressure being placed to breach the mouth once back flooding starts.

THE WAY FORWARD


Lake Sibaya Intermediate EWR

• The workshop to define the Recommended Ecological Category and the Environmental Water Requirements will be held in September 2015.

• The Ecoclassification and EWR reports will be available November 2015

Kosi estuary Rapid EWR

• Will commence in September 2015 • Field surveys during November 2015 – January

2016 • Workshop to define the REC and EWR will be held

in February 2016 • Ecoclassification and EWR report drafted in March

2016

St Lucia / Mfolozi estuary

• Commencement September 2015 • Scenario workshop n October 2015 • Draft report in November 2015

This project is administered by the Chief Directorate: Water Ecosystems.

Project Manager: Yakeen Atwaru

Tel.: 012-336 7500

Email: [email protected]

RESERVE DETERMINATION OF PRIORITY WATER RESOURCES IN …€¦ · The natural, present day and seven...

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