Trading off hydropower potential forirrigated agriculture – an examplefrom the Sesan riverTimo A. Räsänen, Olivier Joffre,...
Background• Sesan River• Hydropower development   • 6 existing and 5 planned large hydropower     projects• Agriculture an...
Aims, focus & approachAim: To assess the impacts of A) irrigation water abstractionfrom reservoir on hydropower generation...
Assessment methodology•   Hydrological modelling (VMod)•   Hydropower modelling (CSUDP)•   Assessment of land use suitabil...
Assessment of land use suitability for irrigated rice• Land suitability was  estimated for 5 km  distance from the Sesan  ...
Assessment of crop water requirement• Crop water requirement was  defined using for                                       ...
Irrigation potential and scenarios• Irrigation potential of each reservoir was based on   • Land suitability   • Crop wate...
Reservoirs with irrigation andassessment scales                                 Catchment                                 ...
Case study reservoir with highirrigation potential• Sesan 3A with high  downstream irrigation  potential• An example where...
Case study: Yali-Sesan 3-Sesan 3A cascade• Simulated annual average  hydropwer generation of  Sesan 3A   • 425-428 GWh• Re...
Catchment scale irrigation scenario for seven  reservoirs: Hydropower • Catchment scale reduction in annual hydropower gen...
Catchment scale irrigation scenario for sevenreservoirs: Hydrology• The hydropower operations increased dry season flows a...
Catchment scale irrigationscenario for sevenreservoirs: Land cover• Hydropower reservoirs inundate land    • Existing rese...
Conclusions and final remarks• Main finding: Irrigation from reservoirs contributed  to minor losses in hydropower generat...
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Trading Off Hydropower Potential for Irrigated Agriculture-An Example from the Sesan River

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Mekong Forum on Water, Food and Energy. 2012. Presentation from Session 4: Food, Water and Energy in Catchments

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Trading Off Hydropower Potential for Irrigated Agriculture-An Example from the Sesan River

  1. 1. Trading off hydropower potential forirrigated agriculture – an examplefrom the Sesan riverTimo A. Räsänen, Olivier Joffre, Paradis Somethand Matti KummuAalto University, FinlandICEM, VietnamITC, Cambodiatimo.rasanen@aalto.fiwww.wdrg.fi
  2. 2. Background• Sesan River• Hydropower development • 6 existing and 5 planned large hydropower projects• Agriculture and crops • Cultivation of cash crops is increasing: Rubber, Coffee, Cassava, Cashew, Soya • Irrigated rice: 28,500 ha in Kontum and Gia Lai and 4,350 ha in Ratanakiri • In Cambodia rice is largely rainfed• Food security • Cambodia and Vietnam are hot spots for food insecurity (UN ESCAP, 2009; FAO, 2012) • Food demand is estimated to double by 2050 in the region (FAO 2010) • Climate variability has increased -> Challenges for food production • Multipurpose reservoirs could potentially contribute to increased agricultural production
  3. 3. Aims, focus & approachAim: To assess the impacts of A) irrigation water abstractionfrom reservoir on hydropower generation and B)hydrological impacts of irrigation and hydropowerFocus: On 7 existing and 4 planned hydropower reservoirsApproach: A) Detailed assessment with case study reservoirand B) assessment of catchment scale irrigationdevelopment
  4. 4. Assessment methodology• Hydrological modelling (VMod)• Hydropower modelling (CSUDP)• Assessment of land use suitability for irrigated rice (LUSET)• Assessment of crop water requirement (FAO CROPWAT 8.0)• Assessment of irrigation potential of each reservoir• Modelling of the trade off’s (CSUDP)
  5. 5. Assessment of land use suitability for irrigated rice• Land suitability was estimated for 5 km distance from the Sesan River• Results: • Three land suitablity classes • Altogether 86,000 ha indentified as potentially suitable Highly suitable Moderately suitable• Assessment is on coarse Marginally suitable scale and includes areas already under cultivation
  6. 6. Assessment of crop water requirement• Crop water requirement was defined using for Weekly irrigation schedule 2500 • Dry season rice, 105 days Cambodia • Wet season rice, 125 days 2000 Vietnam• Average dry season irrigation [m3/ha] 1500 volumes • Cambodia: 13,200 m3/ha 1000 • Vietnam: 12,000 m3/ha• Average wet season irrigation 500 volumes 0 • Cambodia: 2,700 m3/ha 1 5 9 13 17 21 25 29 33 37 41 45 49 [week] • Vietnam: 2,200 m3/ha
  7. 7. Irrigation potential and scenarios• Irrigation potential of each reservoir was based on • Land suitability • Crop water requirement • Specific dry season water allocations: 3%, 5% and 7% of dry season water budget• Seven reservoirs were selected for further assessment• Three irrigation scenarios for Sesan 3A • B2. 3,894 ha dry and wet season rice • B3. 6,490 ha dry and wet season rice • B4. 9,086 ha dry and wet season rice• One catchment scale irrigation scenario for seven reservoirs • 28,348 ha dry and wet season rice (rate of irrigation corresponds to B3)
  8. 8. Reservoirs with irrigation andassessment scales Catchment scale with seven reservoirs Case study reservoir for more detailed assessment
  9. 9. Case study reservoir with highirrigation potential• Sesan 3A with high downstream irrigation potential• An example where irrigation from reservoir could have been implemented• Dowstream area has already large irrigation projects• Sesan 3A reservoir storage is small, requires co-operation with upstream dams Sesan 3 and Yali
  10. 10. Case study: Yali-Sesan 3-Sesan 3A cascade• Simulated annual average hydropwer generation of Sesan 3A • 425-428 GWh• Reduction in annual hydropower generation: • 3,894 ha: -0.6…-0.7% • 6,490 ha: -1…-1.2% • 9,086 ha: -1.4…-1.7%• Reduction in dry season hydropower generation • -1.8…-5.6%
  11. 11. Catchment scale irrigation scenario for seven reservoirs: Hydropower • Catchment scale reduction in annual hydropower generation • 28,348 ha: -1.6 % (209 GWh) • Most significant impacts were experienced in Lower Sesan 3 • -3.4% (56 Gwh) reduction in annual hydropower generation Baseline annual Irrigated area Change in annual Baseline dry season Change in dry season average hydropower average hydropower average hydropower average hydropower generation generation generation generation [GWh] [ha] [%] [GWh] [%]Upper Kontum 1,057 600 -1.9 398 -4.1Plei Krong 497 2,817 -1.4 149 -3.7Yali 3,850 0 -0.6 1,333 -1.6Sesan 3 1,228 0 -0.6 405 -1.6Sesan 3A 454 6,490 -1.7 148 -5Sesan 4 1,478 3,474 -2 449 -6.1Sesan 4 A - 5,091 - - -Sesan 1 641 0 -3.2 271 -7.5Lower Sesan 3 1,634 7,843 -3.4 636 -8.6Lower Sesan 2 2,218 2,033 -1.3 638 -4.3TOTAL 13,056 28,348 -1.6 4,427 -4.2
  12. 12. Catchment scale irrigation scenario for sevenreservoirs: Hydrology• The hydropower operations increased dry season flows and reduced wet season flows • Lower Sesan 3: dry season +167%, wet season -11%• Irrigation of 28, 348 ha reduced the annual river flow by 0.39 km3 which corresponds to 1.9% of the Sesan’s annual average flow 1800 Lower Sesan 3 1600 1400 1200 1000 [m3/s] 800 600 400 200 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  13. 13. Catchment scale irrigationscenario for sevenreservoirs: Land cover• Hydropower reservoirs inundate land • Existing reservoirs 198 km2 • Planned reservoirs 837 km2 • Lower Sesan 3 will inundate 45 000 ha of land defined in this study as potentially suitable for irrigated rice• Expansion of agriculture has already caused deforestation in Sesan catchment • e.g. in Ratanakiri 40% reduction in forest cover between 1997-2005• Irrigation development from Sesan 4, Lower Sesan 3 and Lower Sesan 2 reservoirs have high likelihood of causing further deforestation
  14. 14. Conclusions and final remarks• Main finding: Irrigation from reservoirs contributed to minor losses in hydropower generation • Sesan 3A: 7.3 GWh (1.2%) were traded to 9,100 ha of irrigated rice • Catchment scale: 208.9 Gwh (1.6%) were traded to 28,400 ha of irrigated rice• Impacts of hydropower on river flow were more significant compared to irrigation and impacts were cumulative downstream• Co-ordination between hydropower projects may be required for successful irrigation• This study focused only on technical and hydrological aspects • Social, livelihood and political issues have a major role in sustainable development• Findings of this study prompt further investigations on multi-purpose reservoirs

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