The 6th Scientific PhD Seminar of

the WISDOM project

WATER BALANCE AND

TRANSBOUNDARY IMPACTS

IN THE MEKONG DELTA

SOUTHERN INSTITUTE OF WATER RESOURCES RESEARCH

658 Vo Van Kiet Blvd, District 5, HCM City, Vietnam Tel: +84 8 38380989 Fax: +84 8 39235028

Website: www.siwrr.org.vn

Contents

Overview the Mekong River basin

Water balance in the Mekong Delta

Transboundary Impacts

Impacts to Water requirements

Impacts to hydrology regime in Kratie

Impacts to salinity Intrusion in Mekong Delta

Impact assessment

Considerations

Overview of the Mekong River Basin

No Country Area in the

MK river

basin (km2)

% of the

MK river

basin

% of the

country area

% of water

flow

1

2

China

Myanmar

165.000

24.000

21

3

-

-

16

2

3

4

5

6

Laos

Thailand

Cambodia

Vietnam (MD

& CH)

202.000

184.000

155.000

65.000

25

22

20

9

97

36

86

20

35

18

18

11

Total area

(km2)

795.000 100 Total

annual flow

475 km3

% contribution of water flow in MRB

Dry season

Wet season

The Mekong Delta

Total area of 39,700 km2 or 12.% of

area of Vietnam with 700 km sea lines,

Cultivated area is about 2.4 million

hectares with 7 crops per 2 years,

The population is about 18 million

peoples,

The Mekong Delta contributes 20%

of GDP,

Rice production is at 24.3 millions

tons (55% of country).

Month

Issues

1

2

3

4

5

6

7

8

9

10

11

12

Flood

Salinity intrusion

Acid sulfate soil

and acid water

Drought

Bank Erosion

Sediment

Pollution

Water-related problems in Mekong Delta

Addition threat: upstream development, CC & SWLR

Rainfalls in the Mekong Delta

Rainfalls isoline in the Mekong Delta

River network in the MD

• The Mekong and Bassac rivers flow to the

East Sea via nine river mouths as Tieu, Dai,

Ba Lai, Ham Luong, Co Chien , Cung Hau,

Dinh An, Ba Thac and Tran De.

• Vaico River system runs parallel to the east

of the Mekong River.

• Cai River, My Thanh, Ganh Hao, Ong Doc,

Bay Hap are tidal rivers flow to the West

and East Sea.

• The canal systems have a high density, with

a total of 30,000 - 40,000km of primary and

secondary canals in the Mekong Delta.

Hydrology regime in the MD

Seasonal flooding in the Mekong Delta begins

in months Jun-Jul and ends in months Nov -

Dec, with an average peak flow entering the

delta of around 28,000-30,000 m3/s. The

seasonal average dry flow is about 3,000-5,000

m3/s. Both high and low flood regimes prevail

for about 6 months.

Total average annual river flow in the MD is

~408 billion m3 (2000 - 2008 at Tan Chau and

Chau Doc stations). Flooding over the border

region accounts for 14-18% of the total flood

into the territory of Vietnam (estimated 57

billion m3) and surface water by rain on the

plains accounts for 11% of the whole water

volume (estimated 45 billion m3).

Month Q-Tan Chau

(m3/s)

Q-Chau Doc

(m3/s)

Jan 6.258 1.325

Feb 4.028 741

Mar 2.580 478

Apr 2.244 410

May 3.032 567

Jun 7.391 1.344

Jul 12.756 2.826

Aug 17.849 4.673

Sep 19.907 5.862

Oct 18.234 5.534

Nov 13.358 3.720

Dec 9.212 2.228

Qmax 19.907 5.862

Qtb 9.737 2.476

Qmin 2.244 410

Qavg dry season 4.559 958

Qavg wet season 14.916 3.993

Year Tan Chau Chau Doc

1998 7,184 1,819

2000 12,093 3,323

2001 11,540 3,134

2003 8,905 2,047

2004 9,166 2,183

2005 9,435 2,422

2006 10,055 2,463

Max 12,093 3,323

Mean 9,768 2,484

Min 7,184 1,819

Water level & Discharge of high floods at Tan Chau and Chau Doc

Year Tan Chau Chau Doc

Hmax (m) Qmax (m3/s) Hmax (m) Qmax (m3/s)

1961 5,11 28.800 4,94 7.840

1978 4,94 25.600 4,50 7.160

1991 4,80 24.300 4,31 7.660

1994 4,67 23.920 4,27 7.290

1996 5,03 23.200 4,60 8.560

2000 5,06 25.500 4,90 7.660

2011 4,86 26.200 4,23 8.170

Using IQQM model to analyze the water requirements in the

Mekong Delta

• Time series of hydrological data from 1985-2007

• Irrigated areas of 2000, 2030 and 2060

Water requirements

Industry and domestic use

Irrigation

Water demands in Mekong Delta

Min

Tbinh Max

0

200

400

600

800

1000

1200

1400

1 2 3 4 5 6 7 8 9 10 11

12

(m3/s

)

1 2 3 4 5 6 7 8 9 10 11 12

Min 864 923 454 167 360 283 95 36 19 43 100 469

Tbinh 1142 1111 586 568 714 363 271 71 54 72 284 778

Max 1291 1196 710 778 1214 619 606 130 108 117 500 1000

(Data from 1985 - 2007)

Max water demands in the MD

-

500,00

1.000,00

1.500,00

2.000,00

2.500,00

3.000,00

2007

2030

2060

Max water requirement for Irrigation

Legends

Months in

m3/s

0

10

20

30

40

50

60

70

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2007

2030

2060

Water requirements for domestic use

Legends

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2007

1,568.45

1,818.55 765.84

1,733.89 511.61 220.48 184.24 131.78 66.18 24.78

1,143.09

1,610.43

2030

1,903.65

2,207.37 942.95

1,781.04 529.23 236.13 201.55 148.80 83.69 42.28

1,383.12

1,936.57

2060

1,417.69

1,635.92 720.62

2,789.12 901.93 419.13 354.60 265.51 150.49 77.61

1,010.44

1,466.20

POPULATION INCREASE

IRRIGATED AREA INCREASE

HYDROPOWER DAMS INCREASE

DSF (Decision Support Framework)

SWAT

IQQM

MIKE 11

Tool for analyzing

Timeseries spatial

DA

TA

BA

SE

SWAT and IQQM

SWAT IQQM-

Tonlesap lake

MIKE 11

Models using for assessement

Population development in the LMB

Countries National

population

in 2000

(millions)

Rural

area

(%)

The rate of

population

growth(%)

Population and projected

population in LMB

2000 2010 2020

Cambodia 13.1 84 2.3 9.8 13.0 16.5

Lao PDR 5.3 76 2.6 4.9 5.2 7.6

Thailand 62.8 78 1.0 23.1 24.5 28.2

Vietnam 78.1 80 1.4 16.9 17.3 21.8

Total 159.3 54.7 60 74.1

Irrigated areas in Lower Mekong Basin

Locations Numbers of

Irrigation

systems

Wet

season

areas

(ha)

Dry

season

areas

(ha)

Three crops

- areas (ha)

Irrigated

areas

(ha)

Laos 2.532 224.232 151.940 224.232

Thailand 8.764 (840.425) (100.000) 941.425

Cambodia 1.012 248.842 181.506 392.117

Vietnam MD* 85 1.683.094 1.417.549 351.506 1.683.094

Vietnam CH 76 36.008 7.290 36.008

Total 12.469 3.276.876

Source: MRC 2001

Potential suitability land for agricultural

development in LMB

Countries

Suitability land

(million ha)

Irrigated area in

the dry season

(1,000 ha)

Cultivated

existing

(%)

Irrigated area

in the wet

season (%)

Laos 2.7 131.8 2 17

Vietnam CH 0.4 37.0 10 30

Vietnam

MD*

3.3 3,302.2 100 22

Thailand 12.2 155.9 1 12

Cambodia 11.2 250.0 2 11

Total 29.8 3.976.9 13.4 14

Existing and potential Hydropower in

the Mekong River Basin

Existing Hydropower Potential Hydropower

Existing Hydropower in the entire basin is about 53,000 MW, in

which Upper Mekong Basin (China & Myanmar): 23,000MW;

Lower Mekong Basin: 30,000 MW

Hydropower in main stream: 13,000 MW

Hydropower in tributaries: Laos 13,000 MW, Cambodia 2,200 MW,

Vietnam 2,000 MW

Hydropower dams in China

Projects Designed

Capacity

(MW)

Power

(GWh)

Volume

(Million m3)

Basin Area

(km2)

Qtk

(m3/s)

Planned

Gongguoqiao 750 1,670 510 97,300 985

Xiaowan 4,200 18,540 15,130 113,300 1,220 2010-12

Manwan 1,500 7,780 920 114,500 1,230 1993

Dachaosan 1,350 7,090 880 121,000 1,230 2001

Nuozhadu 5,500 22,670 24,670 144,700 1,750 2013-16

Jinhong 1,500 8,470 1,040 149,100 1,840 2012-13

Ganlanba 150 1,010 151,800 1,880

Mengsong 600 3,740 160,000 2,020

Total 15,550 74,060

Total designed water heights of hydropower

dams in China equal the differences of

normal water level of two reservoirs, more

than 700 Km length of Lancang River (the

Upstream of Mekong River) could not be

natural river