1) The document assesses how existing and future hydropower development in the Sekong, Sesan and Srepok rivers of the Mekong Basin could change river flow regimes. 2) It compares the impacts of dams built in tributaries versus the mainstream Mekong on flows and water levels, and examines different scenarios of dam development and operation. 3) The results indicate that future dam development could significantly reduce seasonal flows in the Mekong River, with potential downstream impacts on areas like Tonle Sap and the Mekong Delta.

1. Assessment of Flow Changes from
LOGO
Operations of 41 Dams in the Sekong, Sesan
and Srepok Rivers of the Mekong Basin
Dr. Thanapon Piman and Dr. Tom Cochrane
University of Canterbury
Department of Civil and Natural Resources Engineering
Asia 2012: Water Resources and Renewable Energy Development in Asia
27 Mar 2012, Chiang Mai, Thailand
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2. 3S Basin within the Mekong Basin
 A transboundary river basin in
Lao PDR, Cambodia and Viet Nam
 Hydropower development is
accelerating: Energy demands
 Significant flow contribution to
the Mekong river (17-20%)
 An important contribution of
aquatic biodiversity and
ecosystem services: fish,
habitats, and migration routes
 About 500,000 people are highly
depend on natural resources and
ecosystem services
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3. Objectives
 To assess how existing and future hydropower
development and operation in the 3S rivers can
change flow regimes
 To compare changes in flows and water levels in
the Mekong River
 Mekong tributaries vs. Mainstream dams: which will
cause greater impact?
 To provide strategic options for dam development
and operations in the 3S basin
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4. Simulated scenarios
 Levels of hydropower development
2) Baseline scenario (BL)
 No dams
5) Definite future scenario (DF)
 Existing and under construction dams
8) Development in main tributaries scenario (DMT)
 DF plus proposed dams in main tributaries
• Development in main and sub tributaries scenario (DMST)
 DMT plus proposed dams in sub tributaries or All dams
4

5. Simulated scenarios
Lao PDR Lao PDR Lao PDR
DF DMT DMST
5

6. Simulated scenarios
6

7. Simulated Dam Operation Scenarios
1. Seasonal Variation: Max. energy
2. Full supply: Ecologically friendly
3. Low Supply: Flood control
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8. Hydrologic modelling
 SWAT model (ARCSWAT and
SWAT 2005)
 Set up and calibration by
MRC (2010)
 Simulation period 1986-2006
 Divided into 118 subbasins
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9. Reservoir operation modelling
 Hec Ressim model
(Version 3.0)
 Set up by UC (2011)
 Simulation period 1986-2006
 41 dams are modelled
 Muskingum Cunge 8 points
routing
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10. Seasonal flow changes
10

11. Flow duration curves
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12. Impact of operation rules
12

13. Mekong mainstream dams
Manwan 1995
Xiaowan 2010 Dochushan 2003
Jinghong 2007
Source: MRC 2010
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14. 3S dams vs. mainstream dams
14

15. Changes in flows and WL on mainstream
“Potential downstream
impact on Tonle Sap
and Mekong delta”
Stung Treng
Kratie
15

16. Changes in Mekong mainstream WL
16

17. Changes in Mekong mainstream flows
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18. Conclusions
7,000
6,000 Present
5,000
1) and Future
Flow
4,000
3,000
2,000
m
w
F
3
o
s
)
(
/
l
1,000
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2) 3S dams Chinese dams LMB mainstream dams
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19. Conclusions
3) Site selection, dam operation and
cooperation/coordination are important
4) Further study needs;
 Intra-daily flow fluctuation
 Sediment flows and dam trapping
 Ecosystem and biodiversity impacts
 Social and economic impacts
 Climate change
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20. Conclusions
Maximize Maximize
Hydropower Basin
Benefits Benefits
???
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21. Acknowledgements
 Mekong River Commission: data and information
 The Critical Ecosystem Partnership Fund: a joint
initiative of Conservation International, l’Agence
Française de Développement, the Global Environment
Facility, the Government of Japan, the MacArthur
Foundation and the World Bank. A fundamental goal is
to ensure civil society is engaged in biodiversity
conservation.
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