Estimating Agricultural Water Consumption by Analyzing Water Balance

About two-thirds of rivers, lakes and groundwater are applied for agricultural production in the world. Same as other countries, a significant fraction of surface and groundwater resources are used in agricultural sector in Iran. Water balance at country scale is the origin of estimation of applied water as agricultural consumption. The variability of annual precipitation is as the origin of the components of water balance in hydrological cycle, caused changeability in the water consumption of agricultural sector which are important reasons for estimating and re-estimating consumptive water in agricultural sector. Therefore, in this study, consumptive water of agricultural sector was analyzed based on long term (50 years) and short term (current 7 years) measured data for precipitation with the method of water balance in hydrological cycle in the country. Results revealed that average annual precipitation were 249±53 and 206±33 mm for two long and short studied periods, and the consumption water in agricultural sector were 67 ±18 and 83±6 km3 for long (50 years) and short (7 years) periods for non-modified conditions. The modified consumption water for the short period was 75±6 MCM.Results revealed that for the long period, the water consumption in agricultural sector was 0.50 of renewable water in the country. The outstanding of this study was up to date estimating of the water consumption in agricultural sector and its analysis. But applying water balance method for this purpose has some substantial limitations and non-reliable simplifications. Therefore suitable experiments are needed to reliably the results.