CHANGES IN IRRIGATION WATER USE EFFICIENCY INDICES UNDER THE IMPACT OF UNCERTAINTY OF CLIMATE CHANGE IN THE FUTURE PERIODS CASE STUDY: HASHTGERD PLAIN (IRAN)

摘要

In this paper, the risk analysis of water use efficiency of Hashtgerd plain is describedrnconsidering the uncertainty of AOGCM (Atmospheric Ocean General Circulation Model)rnin simulating climate variables in the future period. The output of nine AOGCMs was usedrnunder the A2 scenario. Using Monte Carlo method, weighting approach, and change factorrndownscaling method, 2000 time series of temperature and precipitation were produced forrnthe study area. AEZ / GIS approach was adopted to calculate potential yield of the cropsrnin 2005 (as the baseline year) and future periods in the study area. Hargrive – Samanirnmethod was used to calculate daily potential and reference evapotranspiration. Using soilrnwater balance model net crop-water requirements of each crop of the study area wererncalculated in 2005 and in the 2010-2100 period. Results shows regional temperaturernincrease in the future years on average between 1.7℃ to 3℃. The average precipitationrnchanges in the region would be between -18 and 20 per cent. The range of changes inrnwater use efficiency for alfalfa, barley, maize and wheat, up to year 2100 are 3.8 - 4.5,rn0.11 - 0.28, 4.7 - 5.45 and 0.04 - 0.1 m~3 kg~(-1) potential, respectively.