Overview of Recent Mekong River Basin Floods

11

Overview of Recent Mekong Overview of Recent Mekong River Basin FloodsRiver Basin Floods

Overview of Recent Mekong Overview of Recent Mekong River Basin FloodsRiver Basin Floods

Third Annual Flood ForumVientiane, Lao PDR

7-8 April 2005

22

1.1. To provide a preliminary overview on To provide a preliminary overview on thethe recent floods recent floods based on limited based on limited data and information received so fardata and information received so far

2.2. To initiate the invitation for To initiate the invitation for increasing increasing timely data and timely data and information sharinginformation sharing among the among the countries in the region for a better countries in the region for a better understanding of floods occurrence understanding of floods occurrence and their impacts in the regionand their impacts in the region

Main ObjectivesMain Objectives

33

Today’s TopicsToday’s Topics

1. Data Used and Analytical 1. Data Used and Analytical toolstools

2.Wet season and flood analysis2.Wet season and flood analysis

3. Rainfall conditions3. Rainfall conditions

4. Conclusion and 4. Conclusion and RecommendationsRecommendations

44

1. Data Used and Analytical 1. Data Used and Analytical ToolTool

Archiving and operational data Daily data up to Mar 05 Rainfall from 16 sta. Flows and water level from 8

sta.

Data UsedData Used

Decision Support Framework (DSF)

Analytical Analytical ToolTool

55

2.Wet season and flood 2.Wet season and flood analysisanalysis

Vientiane City Centre. September. 1966.Vientiane City Centre. September. 1966.

Central Business Area under water for 5 weeks. Central Business Area under water for 5 weeks.

Floodpeak = 26 000 cumecs. (approximately a 1 in 100 year event.)Floodpeak = 26 000 cumecs. (approximately a 1 in 100 year event.)

o Hydrographso Wet season duration

o End date and start dateo Annual flood peak

o Flood frequency analysiso Flow volume

Adamson/03/05

66

Water level of Mekong at Nong Khai

0

2

4

6

8

10

12

14

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

Alarm Flood 1992 1998 2000

2002 2003 2004 Av.80-04Water level of Mekong at Pakse

0.002.004.006.008.00

10.0012.0014.0016.00

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

Alarm Flood 1992 1998 2000

2002 2003 2004 Av.80-04

Water level of Mekong at Chiang Saen

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

Alarm Flood 1992 1998 2000

2002 2003 2004 Av.80-04

Water level of Mekong at Mukdahan

0

2

4

6

8

10

12

14

01-Jun 16-Jun 01-Jul 16-Jul 31-Jul 15-Aug 30-Aug 14-Sep 29-Sep 14-Oct 29-Oct

Time in days

Gau

ge h

eigh

t in

met

res

2004 1992 1998 2000 2002

2003 Av.80-04 Alarm Flood

Chiang Saen-PakseChiang Saen Nongkhai

Mukdahan

HydrographHydrograph

June-October

Pakse

20032003

2004 20032003

2004

20032003

2004

200320032004

average

2000

average

2000

average

2000

average

2000

77

Water level of Mekong at Kompong Cham

0.002.004.006.008.00

10.0012.0014.0016.0018.00

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

Alarm Flood 1992 1998 2000

2002 2003 2004 Av.80-04

Water level of Mekong at Tan Chau

0.00

1.00

2.00

3.00

4.00

5.00

6.00

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

Alarm Flood 1992 1998 2000

2002 2003 2004 Av.80-04

Water level of Bassac at Phnom Penh

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

1992 1998 2000

2002 2003 Av.80-04

Alarm Flood 2004

Water level of Mekong at Kratie

0.00

5.00

10.00

15.00

20.00

25.00

01-Jun

16-Jun

01-Jul

16-Jul

31-Jul

15-Aug

30-Aug

14-Sep

29-Sep

14-Oct

29-Oct

Time in days

Gauge h

eig

ht in

metr

es

Alarm Flood 1992 1998 2000

2002 2003 2004 Av.80-04

Kg. Cham

Tan Chau

June-OctoberKratie-Tan ChauKratie

Phnom Penh


20032003 200420032003

2004

20032003

2004

200320032004

average2000

average

2000

average2000

average

2000

Jun-Oct 2003: Mekong water levels are lower than the normal level

Jun-Oct 2004: Mekong water levels fluctuate around the normal level

88

Wet Season DurationWet Season Duration

Average_AllD_Var1gfedcb 2004_Var1gfedcb 2003_Var1gfedcb 2002_Var1gfedcb 2001_Var1gfedcb2000_Var1gfedcb 1966_Var1gfedc 1992_Var1gfedcb

15Dec

01Dec

15Nov

01Nov

15Oct

01Oct

15Sep

01Sep

15Aug

01Aug

15Jul

01Jul

15Jun

01Jun

15May

01May

15Apr

01Apr

15Mar

01Mar

15Feb

01Feb

15Jan

01Jan

12,500

12,000

11,500

11,000

10,500

10,000

9,500

9,000

8,500

8,000

7,500

7,000

6,500

6,000

5,500

5,000

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

Flow Hydrograph of Selected years

Tentative Threshold=1,730m3/s

Average

Wet Season

Flood Event Analysis Tool used to define tentative threshold value and wet season

Threshold value= e.g. 50% of flow values over a period of 01/01/1960-28/03/2005

99

Chiang Saen

Wet Season DurationWet Season Duration

: Time Series Chart

[Th=1730cumecs, MinEvLen=1, MinIntLen=0]

Chiangsen_obs (11/Jun/1960)gfedcb Chiangsen_obs (22/Jun/1960)gfedcb Chiangsen_obs (02/Dec/1960)gfedcbChiangsen_obs (09/Jun/1965)gfedcb Chiangsen_obs (07/Jun/1966)gfedcb Chiangsen_obs (11/Jun/1970)gfedcbChiangsen_obs (26/May/1971)gfedcb Chiangsen_obs (13/Jun/1980)gfedcb Chiangsen_obs (16/Jun/1993)gfedcbChiangsen_obs (26/Jun/1993)gfedcb Chiangsen_obs (16/Dec/1993)gfedcb Chiangsen_obs (15/May/2000)gfedcbChiangsen_obs (13/May/2001)gfedcb Chiangsen_obs (28/May/2001)gfedcb Chiangsen_obs (08/Dec/2001)gfedcbChiangsen_obs (31/Dec/2001)gfedcb Chiangsen_obs (14/May/2002)gfedcb Chiangsen_obs (12/Jun/2002)gfedcbChiangsen_obs (22/Nov/2002)gfedcb Chiangsen_obs (26/Nov/2002)gfedcb Chiangsen_obs (10/Dec/2002)gfedcbChiangsen_obs (06/Jan/2003)gfedc Chiangsen_obs (07/Jun/2003)gfedcb Chiangsen_obs (15/Jun/2003)gfedcbChiangsen_obs (20/May/2004)gfedcb Chiangsen_obs (18/Jun/2004)gfedcb

Day in Year25/Dec10/Dec25/Nov10/Nov26/Oct11/Oct26/Sep11/Sep27/Aug12/Aug28/Jul13/Jul28/Jun13/Jun29/May14/May

(cum

ecs)

22,000

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

Flow event over threshold Wet Season Duration Analysis_ Chiangsen

Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:

Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcb

Cumulative Exceedence Percentile %10095908580757065605550454035302520151050

Even

t Dura

tion (

days

)

240

235

230

225

220

215

210

205

200

195

190

185

180

175

170

165

160

155

150

195 days

Average: 195 Days

------------------------Y2000: 207 Days

Y2001: 237 Days

Y2003: 148 Days

Y2004: 179 Days

Wet Season Duration Analysis

1010

: Event Start Date AnalysisChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution: Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:

Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcbChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (99-04)gfedcb

Day in Year25/Dec25/Nov26/Oct26/Sep27/Aug28/Jul28/Jun29/May29/Apr30/Mar28/Feb29/Jan

Cum

ula

tive E

xceedence P

erc

entil

e %

100

95

9085

80

75

70

6560

55

50

45

4035

30

25

20

1510

5Start Date: 30May

Chiang Saen

Start Date and End DateStart Date and End Date

: Event End Date AnalysisChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution: Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:

Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcbChiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (99-04)gfedcb

Day in Year25/Dec25/Nov26/Oct26/Sep27/Aug28/Jul28/Jun29/May29/Apr30/Mar28/Feb29/Jan

Cum

ula

tive E

xceedence P

erc

entil

e %

100

95

9085

80

75

70

6560

55

50

45

4035

30

25

20

1510

5

End Date: 5 Dec

1111

Chiang Saen

Annual Flood PeakAnnual Flood Peak

: Peak Value Data

Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: Freq. Distribution:

Chiangsen_obs:[Th=1730cumecs, MinEvLen=30, MinIntLen=30],Period: (60-04)gfedcb

Date05/Dec/200307/Dec/199509/Dec/198711/Dec/197913/Dec/197115/Dec/1963

Flo

w (

cum

ecs)

23,000

22,000

21,000

20,000

19,000

18,000

17,000

16,000

15,000

14,000

13,000

12,000

11,000

10,000

9,000

8,000

7,000

6,000

Average Flood Peak: 10,522 m3/s2004

2003

1212

Chiang Saen

Flood Frequency AnalysisFlood Frequency Analysis

Annual Flood Frequency AnalysisChiangsen_obs - Freq. Distribution: Gumbel (EV1) & GEV

Chiangsen_obs - Hazen (1960-2004)gfedcb EV1 Chiangsen_obs - HazengfedcbGEV Chiangsen_obs - Hazengfedcb

Return Period (years)1 2 4 5 10 20 25 50 100 200 500

(cum

ecs)

34,000

32,000

30,000

28,000

26,000

24,000

22,000

20,000

18,000

16,000

14,000

12,000

10,000

8,000

6,000

4,000

2,000

0

20042003

1313

Chiang Saen

Flow VolumeFlow Volume

6.839E+106.956E+10

8.554E+10 8.554E+10

7.305E+10

4.725E+10

6.997E+10

0.000E+00

1.000E+10

2.000E+10

3.000E+10

4.000E+10

5.000E+10

6.000E+10

7.000E+10

8.000E+10

9.000E+10

Avge_1960_2004

19992000

20012002

20032004

Flo

od

_V

olu

me

Flood_Volume

Comparison Wet Season flow Volume at Chaingsen

Year

1414

SummarySummaryStation Indicators Avg. 1978 2000 2001 2002 2003 2004

Chiang Saen

Duration (Days) 196 189 207 237 242 148 179

Start Date 30-May 15-May 15-May 13-May 14-May 07-Jun 20-May

End Date 05-Dec 20-Nov 08-Dec 05-Jan-02 11-Jan-03 02-Nov 15-Nov

Peak (cms)

Tr (yr)

10,522 11,400

3

10,700

2

10,700

2

12,700

4

6,880

<2

10,715

2

Volume(m3) 6.84E+10 8.58E+10 8.55E+10 8.54E+10 7.31E+10 4.73E+10 7.00E+10

Pakse Duration (Days) 187 188 202 203 207 161 170

Start Date 04-Jun 28-May 14-May 26-May 23-May 03-Jun 29-May

End Date 05-Dec 02-Dec 02-Dec 15-Dec 16-Dec 11-Nov 15-Nov

Peak (cms) 36,807 56,000 45,148 42,318 39,343 34,159 38,556

Volume(m3) 3.20E+11 4.02E+11 4.01E+11 3.88E+11 3.97E+11 2.59E+11 3.09E+11

Kratie Duration(Days) 183 216 206 213 174 162

Max. WL (m) 21.45 23.08 23.37 22.97 20.98 21.19

Phnom Penh

Duration(Days)

Max. WL (m) 8.6 11.21 10.77 10.09

1515

Seasonal Flood Hydrograph Seasonal Flood Hydrograph VolumeVolumeYear

Chiang Saen

Luang Prabang

Chiang Khan

VTE Nakhon Phanom

Mukd’an Khong Chiam

Pakse Stung Treng

Kratie

1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Seasonal flood hydrograph volume (SFHV)

SFHV below “normal”, less than the 1:2 yr ARI

SFHV> 2 and < 5 yr ARI



SFHV> 20 yr ARI

Figure 5.1 The flood history of the Lower Mekong Basin 1960 to 2003. The analysis is based on a statistical analysis of the annual volumes of flow during the six flood months (June to November).

Overview Mekong Hydrology, November 2004, p.35

1616

3.Rainfall 3.Rainfall conditionsconditions

1717

Chiang Saen

0

400

800

1200

1600

2000

2400

Jun Jul Aug Sep Oct Nov Dec. Jan Feb

Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-93 1998-992000-01 2003-04 2004-05

Luang Prabang

0

400

800

1200

1600

2000

2400


Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-93 1998-992000-01 2003-04 2004-05

Average Annual Rainfall by Sub-basin

Rainfall ConditionsRainfall ConditionsJun-Feb

average

2004

average2004

Mukdahan

0

400

800

1200

1600

2000

2400


Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-03 1998-992000-01 2003-04 2004-05

Pakse

0

400

800

1200

1600

2000

2400


Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-93 1998-992000-01 2003-04 2004-05

average

2004

average

2004

Stung Treng

0

400

800

1200

1600

2000

2400


Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-93 1998-992000-01 2003-04 2004-05

Phnom Penh

0

400

800

1200

1600

2000

2400


Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-93 1998-992000-01 2003-04 2004-05

average

2004

average

2004

Chau Doc

0

400

800

1200

1600

2000

2400


Acc

um

ula

tive

Ra

infa

ll (m

m).

Average 1992-93 1998-992000-01 2003-04 2004-05

average

2004

1818

0

200

400

600

800

1000

1200

1400

1600

Jun Jul Aug Sep Oct Nov Dec Jan Feb

Acc

umul

ativ

e R

ainf

all (

mm

).

1992-93 1998-99 2000-01

2003-04 2004-05 Average

•Rainfall average from 16 sites across the lower Mekong Basin

Rainfall Conditions Rainfall Conditions (con’t)(con’t)

Over the Basin

• 2004-05 rainfall (averaged from 9 stations)

Average

2003

2004

Jun-Feb

RainfallGenerally lower than normal rainfall esp. during the end wet season 2003 and 2004 after September

1919

1

10

100

1000

2004

2004 2004

2004

average

JanuaryFebruary

March

AprilMayJune

JulyAugust

September

OctoberNovemberDecember

3 month rainfall total

(mm)

Khon Kaen

Regionally during 2004, Regionally during 2004, rainfall during the first rainfall during the first 9 months of the year 9 months of the year was generally above was generally above average average

However, during the 4However, during the 4thth quarter of the year there quarter of the year there was little or no rainfall, was little or no rainfall, indicating an indicating an uncharacteristically uncharacteristically early end to the 2004 wet early end to the 2004 wet season.season.

Taking the year as a Taking the year as a whole, however, total whole, however, total rainfall during 2004 was rainfall during 2004 was average.average.

Rainfall 1Rainfall 1stst quarter 2 quarter 2ndnd quarter 3 quarter 3rdrd quarter 4 quarter 4thth quarter Year quarter Year

(mm) Jan - Mar Apr – Jun Jul – Sep Oct – Dec(mm) Jan - Mar Apr – Jun Jul – Sep Oct – Dec

Average Average

1950 -2004 60 410 620 130 1220 mm1950 -2004 60 410 620 130 1220 mm

2004 80 520 625 2 1227 mm2004 80 520 625 2 1227 mm

% average 133% 127% 100% <2% 100 % % average 133% 127% 100% <2% 100 %

KHON KAEN : Historical context of rainfall in 2004KHON KAEN : Historical context of rainfall in 2004

Adamson/03/05

2020

Seasonal percentage of normal rainfall: Oct 2004-Mar 2005Seasonal percentage of normal rainfall: Oct 2004-Mar 2005

Adamson/03/05

Seasonal % of Seasonal % of normal rainfall normal rainfall

October 1October 1stst 2004 2004

toto

March 30March 30thth 2005 2005

Although the image Although the image indicates less than 50% indicates less than 50% of normal seasonal of normal seasonal rainfall…………….rainfall…………….

… …..over most of NE over most of NE Thailand and Central Thailand and Central Laos the proportion was Laos the proportion was in fact between 0% in fact between 0% and 10% of normaland 10% of normal

Source: USDA Website:www.fas.usda.govSource: USDA Website:www.fas.usda.gov

2121

SE ASIA : INDEX OF CROP SE ASIA : INDEX OF CROP STRESS ON MARCH 20STRESS ON MARCH 20THTH 2005 2005

The early end to the 2004 wet season caused The early end to the 2004 wet season caused extremely low levels of reservoir storage and extremely low levels of reservoir storage and river flows which reduced the irrigation river flows which reduced the irrigation water available and increased pumping costs water available and increased pumping costs from rivers.from rivers.

Crop stress, caused by a lack of water is Crop stress, caused by a lack of water is particularly evident in Bangladesh, Yunnan, particularly evident in Bangladesh, Yunnan, Burma, Laos, Thailand and the southern Burma, Laos, Thailand and the southern provinces of Vietnam provinces of Vietnam

Source: USDA Website:www.fas.usda.govSource: USDA Website:www.fas.usda.gov

Adamson/03/05

http://www.fas.usda.gov/pecad/highlights/2005/03/sedrought/seasiadrought.htm

SPOT-veg NDVI Departure from 4-yr Average (derived from satellite imagery) March 20, 2005

2222


Flood peaks and flow volumes in 2003 and 2004 wet seasons are slightly below or comparable

with the average value.

During 2003 wet season, Mekong water levels are lower than the average while fluctuate

around the normal during the wet season in 2004.

Rainfall in basin was found to be lower than the normal esp. during the end of wet season after

September in 2003 and 2004, possibly resulting the lower than normal flows in the consequent

dry seasons.

Timely data and information sharing among the countries in the region is indispensable for

further detailed studies of flood occurrence and their impacts.

2323


For a better understanding in the flood occurrences and their impacts, more

comprehensive studies should be carried out on:o Bivariate distribution of annual flood peak and volume

o Spatial rainfall distribution o Flood duration map, flood depth map, salinity intrusion map

and etc.oStatus of reservoir lake as compared to average, maximum

and minimum levelo etc…

Time series analytical tool in DSF is useful to analyse flood characteristic.

Mekong at Vientiane: Bivariate distribution of annual flood peak and volume. Note the 1966 event compared to the 1: 100 year bivariate relationship between peak & volume

1:100 year envelope

Adamson/03/05

2424

THANK YOU

THANK YOU

2525

4.Dry Season and Low flow 4.Dry Season and Low flow analysisanalysis

o Hydrographso Low flow frequency analysis

2626

Water level of Mekong at Chiang Saen

-1.00

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es

2003-04 Minimum Water Level 2001-02 1992-93Average1980-03 2004-05

Water level of Mekong at Nong Khai

0.00

1.002.00

3.004.00

5.00

6.007.00

8.009.00

10.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es

2003-04 Minimum Water Level2001-02 1992-93Average1980-03 2004-05

Water level of Mekong at Pakse

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es


Water level of Mekong at Mukdahan

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es

2003-04 2004-05 Average1980-031992-93 2001-02 Minimum WL

Chiang Saen-PakseChiang Saen Nongkhai

Mukdahan

November-May

Pakse

2003-20042003-2004

average

2003-20042003-2004

average

2003-20042003-2004

average

2003-20042003-2004

average

2004-2005 2004-2005

2004-2005 2004-2005

Upper PartMekong water levels fluctuate around the normal level, slightly higher than previous year dry season (2003/04) at present


2727

Water level of Mekong at Tan Chau

-1.00

-0.50

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es

2003-04 Minimum Water Level 2001-02

1992-93 Average1980-03 2004-05

Water level of Mekong at Kratie

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es


Water level of Mekong at Kompong Cham

0.00

2.00

4.00

6.00

8.00

10.00

12.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es


Water level of Bassac at Phnom Penh

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

01-N

ov

01-D

ec

31-D

ec

30-J

an

29-F

eb

30-M

ar

29-A

pr

29-M

ay

Time in days

Gauge h

eig

ht in

metr

es

2003-04 2001-021992-93 Average1980-032004-05 Minimum Water Level

Kg. Cham

Tan Chau

November-MayKratie-Tan ChauKratie

Phnom Penh

2003-20042003-2004average2003-20042003-2004

average

2003-20042003-2004

average

2003-20042003-2004

average

2004-20052004-2005

2004-20052004-2005

Lower Part (Kg.Cham downward)

Mekong water levels are very low compared with normal level, comparable or slightly worse than previous year dry season (2003/04)


2828

Return periods for low water levels in February 2005

Frequency AnalysisFrequency Analysis

Station DataWater Level in February

Min Mean

Chiang Saen 1961-2004 < 2 < 2Nongkhai 1960-2004 9 3Mukdahan 1960-2004 4 3Pakse 1960-2004 2 < 2Kratie 1980-2004 < 2 < 2Kg.Cham 1960-2004 8 7Phnom Penh 1960-2004 23 29Tan Chau 1980-2004 49 16

Unit: Year

Water Level

2929

ConclusionConclusion

Comparing with previous year, water level at present is slightly higher in the upper part (Chiang Saen to Kratie) but comparable or

slightly worse in the lower part (from Kompong Cham downward).

Water levels in upper part (from Chiang Saen to Kratie) fluctuate around the normal level while

very low compared with the normal level in lower part (from Kompong Cham downward)

More intensive rainfall data are indispensable for detailed analysis. Low flows are possibly a

result of low rainfall especially during the end of 2004 wet season

3030

Vegetative Index (Vins)-Vegetative Index (Vins)-NDVINDVI

Overview of Recent Mekong River Basin Floods

Documents

Transcript of Overview of Recent Mekong River Basin Floods