Investigation of the effect of climate change on evapotranspiration and wheat water requirement in Bojnord region

There is a general consensus among climate scientists about the rise in global temperature due to an increase in the anthropogenic greenhouse gases in the earth's atmosphere. This will undoubtedly change the pattern of evapotranspiration (ET) due to an increase in CO2 concentration of the air with the resultant deerease in the stomata opening. Predication of the wheat plant ET was achieved by entering the minimum and maximum air temperature, precipitation and daily radiation for the 1983-2012 period into the downscaled LARS-WG software and its incorporation into the HadCM3 general circulation model under the A1B, A2 and B1 climate change scenarios for the 2011-2040 , 2041-2070, and 2071-2100 periods. Results of the general circulation model for Bojnourd area indicates that the temperature will increase in all months of the year up to 2100 year. There will also be an increase in precipitation, in December, January, February and March, and its decreases in April, May, August and September. The generated temperature and precipitation date were fed into the SSM-WHEAT as an application for making changing planting date for simulation of wheat growth. Results indicated that the change in the mean maximum and minimum temperature and also that of precipitation reduced rate-fed wheat's ET up to the year 2100. On the contrary, the ET of the late-planted irrigation wheat will be increased and it would be decreased in rainfed farming.