Assessment of Changes in Yield and Agricultural Water Productivity of Hashtgerd Plain Affected by Climate Change in the Future Periods Using AEZ/GIS Approach

In this research the impact of climate change on crop yield، and water requirement of the main crops (wheat، barley، corn and alfalfa) has been evaluated in Hashtgerd plain with respect to the uncertainty of Atmospheric Ocean General Circulation Models (AOGCMs). To produce monthly temperature and precipitation scenarios،، temperature and precipitation were extractedfrom nine AOGCMs under the A2 emission scenario (CCSM3، CGCM3، CSIRO Mk3، GFDL CM2. 1، GISS ER، HadCM3، ECHAM5، MIROC-med، PCM) in the period 2010-2100 AD. Using Monte Carlo and weighting methods، 2000 time series of temperature and precipitation scenarios were produced for each cell (5°×5°) in the whole plain. Afterwards، these scenarios were downscaled by change factor method for the area. Finally، using AEZ/GIS and Hargreeves-samani approach، the potential yield، and the crop evapotranspiration was assessed in the region in the period 2010-2100. The agricultural water productivity was also studied in this plain.، The results were depicted in range of variation in each period. On the whole، variation of the results revealed the enhancement of water requirement and reduction of the yield in the future periods in this area. Water requirement increase in wheat 15-28، maize 9-14،alfalfa 18/6-34/7 and barely 10-21 millimeter in each periods to 2100 year. On the other hand the range of decrease for wheat، barely، alfalfa and maize will be 50-138، 44-136، 327-508 and 17-24 kilogram per hectare respectively. The results also showed decrease in variation of water productivity in all crops in future periods. Furthermore، in this regard، alfalfa has had the biggest (104-156 gram per Cubic Meter) and wheat the smallest (55-93) reduction in productivity.