geographic and seasonal distribution of water availability in the sesan central highlands
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Mekong Forum on Water, Food and Energy. 2012. Presentation from Session 2: The Values of Multiple UsesTRANSCRIPT
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GEOGRAPHIC AND SEASONAL DISTRIBUTION OF WATER AVAILABILITY IN THE SESAN CENTRAL HIGHLANDSTarek Ketelsen, Mai Ky Vinh, Jorma Koponen
MK2: Valuing Multiple uses of reservoir waters: WorldFish – ICEM –IFPRI – CIEM – DLOF - CEPA
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Sesan Vietnam: land use2005-2009• forested areas rapidly converted
into agricultural land with the expansion of industrial crops– cassava, rubber and coffee
• cashew, rubber, cassava and black pepper are the fastest growing crops (growth of 8-12% p.a.)
• Irrigated rice growing at 3.9%p.a.• Rainfed rice & maize shrinking at
5-7% p.a.
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Sesan Vietnam: catchment characteristics
• 3S catchments are highly productive catchments
• 10% of the total Mekong Basin area but contribute 20.5% of the total flow
• Strong monsoon climate => water availability is a question of timing rather than quantity
• Sesan catcment:18,684km2• Sesan Mean annual outflow:
651m3/s (20.5 billion m3/yr)
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Purpose of the water balanceAssess:• Surface water resource availability in the
Sesan Vietnam• Contribution of reservoirs (Yali) to surface
water availability• Identify which areas of agricultural land could
benefit from reservoir irrigation
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Modelling methodology• VMod model (Koponen et al, 2010)• area-based distribution of hydro-
meteorological impacts of climate change• Computes water balance for grid cells
(5x5km)• Baseline:1981 – 2005• Can predict changes in:
– Rainfall– Runoff– Flows– Infiltration– evapotranspiration
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water balance components
Precipitation
Transpiration
Evaporation
Surface run-off
Infiltration
Surface layer water availability
Subsurface layer water availability
Groundwater availability
• Moisture budget– Surface water
availability– Relationship between
precipitation and PET
• Soil water availability– Moisture stored in
the surface and subsurface layers
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Sesan Vietnam: Rainfall
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Sesan Vietnam: moisture budgetsprecip. - PET
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Sesan Vietnam: Water availability
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Sesan Vietnam: Soil moisture availability
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Sesan Vietnam: “Agricultural drought”Precipitation < 0.5* PET
• Districts surrounding Sesan hydropower are ‘hotspots’ for agricultural drought during the dry and transition seasons– Sathay– Ia Grai– Kon Tum– Chu Pah
• Agricultural land in these areas could benefit from reservoir irrigation to:– Expand agriculture into new areas– Reduce rising demand for
groundwater irrigation in the Sesan
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Catchment water availability• Northern mountainous districts
in Kon Tum are wettest (e.g. Dak Glei)
• Southern districts in Gia Lai are driest (e.g. Chu Se)
• Central districts of Sesan Vietnam are more prone to water stress or extreme dry periods
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Reservoir contribution to water availability• Reservoirs regulate the
seasonal availability of water increasing productivity for electricity generation
• Can they also improve agricultural productivity?
• Which contribution is more valuable?
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Yali Buffer zone• Within 2km of the
reservoir• Sa Thay, Kon Tum
and Chu Pah districts
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Yali buffer zone
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Yali: inflow hydrology• Contributing catchment:
3,878km2• Mean annual flow:
262m3/s (40-950m3/s)• Annual inflow volume:
47,327 – 175,434 m3 (average: 98,724m3)
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Yali reservoir storage• Drawdown :25m (515-490masl)• Drawdown area: 30.2km2• FSL Vol: 981.5mcm• LSL Vol: 215.5mcm• Live storage: 766mcm• Evaporation losses: ~50mcm/yr• => ~700mcm of ”productive water”
Source: (Räsänen et al, 2012
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Reservoir water productivity
• ~700 mcm of productive water• => 3,600-3,800GWh• => USD ?• How much water could be used in surrounding agricultural
land?• How productive would this water be compared to hydro-
electric generation?
Source: (Räsänen et al, 2012
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Thank you!