Water Supply and Demand in Major Irrigation Systems in the Zayendeh Rud Basin.
2006
Ma`man Push, Ali Reza | Miran Zadeh, Mokhtar | Kaka`i, Maid
The purpose of this paper is to study the water supply and demand for major irrigation systems in the Zayandeh Rud Basin. Both temporal (monthly) and spatial (between systems) differences are analyzed. Estimating water supply is fairly straightforward, using the precipitation and water release data collected by the relevant government agencies. But the estimation of water demand is far more difficult due to the absence of reliable data on irrigated areas and cropping patterns. An empirical interpolation procedure was therefore devised to derive this information from the available district-level agricultural statistics for Esfahan Province. The monthly water demands of each of the five irrigation systems and for the year of 1381-82 being studied are computed by applying the crop water requirements obtained through the FAO-CROPWAT program to the irrigated areas and cropping patterns thus obtained. Water supply and water demand in the irrigation systems are then compared, and spatial and temporal in regard to water surplus and deficit are analyzed. It appears that groundwater plays a crucial role in maintaining high levels of cropping intensitiesthe conjunctive use of surface and ground water merits further study in order to get a more comprehensive picture of the overall water supply and demand in the Zayandeh Rud Basin. The importance of systematic, regular monitoring to provide reliable data on irrigated areas, crops, water deliveries and operational practices to help assess and improve irrigation system performance is also highlighted.
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