Mekong Forum on Water, Food and Energy. 2012. Presentation from Session 7: Dams, Livelihoods and Flows

1. A positive effect of hydropower development
on water availability for irrigation. The case of
the Nam Ngum River in the Lower Mekong
Basin
Somphasith Douangsavanh, IWMI-SEA
Guillaume Lacombe, IWMI-SEA
Justin Baker, RTI International
Chu Thai Hoanh, IWMI-SEA
Chanseng Phongpachith, MoNRE
The Mekong Forum on Water, Food and Energy
Hanoi, Vietnam, November 13-14, 2012
Water for a food-secure world

2. Introduction
• Population growth and economic
development in SEA induces increase in food
& energy demand
• Several studies have focused only on negative
impacts of hydropower dams
• In contrast, hydropower development could
compliment irrigation development
Water for a food-secure world

3. Study Area
Nam Ngum Basin: one of the
most important in Lao PDR
(flow, population, food
production & irrigation)
Upstream: hydropower dev
Downstream: irrigation dev in
Vientiane Plain
Water for a food-secure world

4. Research Question
• What are the effects of existing and proposed
hydropower development on water
availability for irrigation in the Nam Ngum
Basin
Water for a food-secure world

5. Methodology
• Assessed current and potential irrigation
water demand from satellite images, cropping
calendar & simple crop water balance
• Analysed flow data recorded over 1962-2009
in combination with an optimized reservoir
system model
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6. Methodology cont
Assessed irrigation water
demand (WD)
where
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7. Methodology
cont
Analyzed flow data recorded
since 1962-2008
1972
1974
1976
1978
1987
1989
1991
1993
2004
2006
2008
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1973
1975
1977
1979
1980
1981
1982
1983
1984
1985
1986
1988
1990
1992
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2005
2007
Hydrological years:
Time periods: TP1 TP2
NN1 stages: NO DAM 2 TURBINES 4 TURBINES 5 TURBINES
NO WATER DIVERSION 1 DIVERSION 2 DIVERSIONS
NN1 Turbine
NN1 spillway
Hinheup
Thalat
Pak Kanhoung
Tha Ngon
Na Luang
Nam Leuk diversion
Nam Song diversion
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8. Structure and functioning of the
model
Each dam represented by a
water balance equation:
Δvolume = Σ inflow – Σ outflow
Power = Turbine flow × Diff
water level × Constant
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9. Results
Seasonal variability flow at Tha Ngon gauging. (a) no dams_1962-1971;
(b) existing dams; (c) full hydropower dev_2030
a b
c
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10. Results cont
Water availability and water supply at the Tha Ngon
gauging station in the Vientian Plain
a b
203m3.s-1
WD2
c
227m3.s-1 155m3.s-1 WD3H
WD3L
Water for a food-secure world

11. Conclusions
• Water demand WD1 would not respect the
environment flow requirement in the dry
years if no dams existed in the Nam Ngum
Basin
• Dry season flow is expected to increase by
>200% and wet season, to decrease by 20%
• Full hydropower development could allow
current irrigation water demand to triple
( 20,824ha-56,376ha)
Water for a food-secure world

12. Thank you
Water for a food-secure world