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Mekong Forum on Water, Food and Energy. 2012. Presentation from Session 7: Dams, Livelihoods and Flows
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Water for a food-secure world
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-SEAJustin Baker, RTI InternationalChu Thai Hoanh, IWMI-SEAChanseng Phongpachith, MoNRE
The Mekong Forum on Water, Food and Energy Hanoi, Vietnam, November 13-14, 2012
Water for a food-secure worldWater for a food-secure world
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 worldWater for a food-secure world
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 worldWater for a food-secure world
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 worldWater for a food-secure world
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
Water for a food-secure worldWater for a food-secure world
Methodology cont
Assessed irrigation water demand (WD)
where
Water for a food-secure worldWater for a food-secure world
Methodology cont
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Time periods:NN1 stages:
Hydrological years:
4 TURBINES1 DIVERSION 2 DIVERSIONS
5 TURBINESTP2
NO WATER DIVERSION
TP1NO DAM 2 TURBINES
Nam Song diversion
Na LuangTha Ngon
Pak KanhoungThalat
HinheupNN1 spillwayNN1 Turbine
Nam Leuk diversion
Analyzed flow data recorded since 1962-2008
Water for a food-secure worldWater for a food-secure world
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
Water for a food-secure worldWater for a food-secure world
Results Seasonal variability flow at Tha Ngon gauging. (a) no dams_1962-1971; (b) existing dams; (c) full hydropower dev_2030
a b
c
Water for a food-secure worldWater for a food-secure world
Results cont Water availability and water supply at the Tha Ngon gauging station in the Vientian Plain
WD2
203m3.s-1
227m3.s-1 155m3.s-1
WD3L
WD3H
a b
c
Water for a food-secure worldWater for a food-secure world
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 worldWater for a food-secure world
Thank you