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1 Hessari, B.; Abbasi, F.; Akbari, M.; Bruggeman, A.; Oweis, T.; De Pauw, E. 2009. Assessment of potential supplemental irrigation impacts on downstream flows in the Karkheh River Basin of Iran. In Humphreys, E.; Bayot, R. S. (Eds.). Increasing the productivity and sustainability of rainfed cropping systems of poor smallholder farmers: proceedings of the CGIAR Challenge Program on Water and Food, International Workshop on Rainfed Cropping Systems, Tamale, Ghana, 22-25 September 2008. Colombo, Sri Lanka: CGIAR Challenge Program on Water and Food. pp.233-241.
(Location: IWMI HQ Call no: 631 G000 HUM Record No: H042443)
(8.92MB)
Supplemental irrigation (SI) is applied in rainfed systems to alleviate soil moisture stress for improved crop yields and water productivity. However, SI developments upstream impact on the amount and quality of water flowing downstream. Runoff in the upper Karkheh River Basin in Iran was assessed using a simple water balance in a GIS framework. The potential flow changes under SI strategies were assessed at the upstream sub-basin scale. Water demand and runoff maps were then simulated for a range of rainfall and irrigation scenarios. Three runoff/flow scenarios were considered: average rainfall, average rainfall with an environmental flow allocation (15% of the mean annual runoff) and low rainfall. The water requirement for SI was assessed under two irrigation scenarios: a single irrigation for early sowing (75 mm in autumn); two irrigations in spring (150 mm total). A FORTRAN program was prepared to calculate the water allocations for the upstream sub-basins. The impacts of the different scenarios on stream-flow were evaluated for each sub-basin and subsequently at the basin scale by comparing the flow with and without the SI scenarios, for the three flow/runoff situations,. The results indicated that early sowing SI allocation in an average rainfall year will decrease downstream flow by about 15% annually, while full spring SI under dry conditions will reduce the amount by about 10%, if all potential areas for SI are developed.
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