Geographic and Seasonal Distribution of Water Availability in the Sesan Central Highlands
GEOGRAPHIC AND SEASONAL DISTRIBUTIONOF WATER AVAILABILITY IN THE SESANCENTRAL HIGHLANDSTarek Ketelsen, Mai Ky Vinh, Jorma Koponen MK2: Valuing Multiple uses of reservoir waters: WorldFish – ICEM –IFPRI – CIEM – DLOF - CEPA
Sesan Vietnam: land use 2005-2009 • 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.
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)
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
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
water balance components • Moisture budget – Surface water availability – Relationship between Precipitation precipitation and PET • Soil water availability Transpiration – Moisture stored in the surface and subsurfaceEvaporation layers Surface run-off Surface layer water availability Subsurface layer water availability Infiltration Groundwater availability
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
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
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?
Yali Buffer zone• Within 2km of the reservoir• Sa Thay, Kon Tum and Chu Pah districts
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