Investigation of the effect of climate change on net irrigation requirement of main crops of Hamadan-Bahar plain using LARS-WG downscaling model

Climate change and its impacts on water recourses is known as one of the most important challenges which human would be faced with it in the future century. In this study, the effect of this phenomenon on net irrigation requirement of main crops of Hamedan- Bahar plain (winter wheat, barley, potato, sugar beet, maize (grain), Peas and onion) was investigated in three next decades. For this purpose, first of all, the capability of LARS-WG5 model was investigated and verified to simulate meteorological variables including minimum and maximum temperature, solar radiation and precipitation at Hamedan synoptic station in the baseline period (1981-2010). In the next step, meteorological variable values were stimulated by HadCM3 model based on A1B, A2 and B1 emission scenarios in the period of 2011-2040. Finally, the net irrigation requirement values of main crops were estimated for base line and three future decades. Based on the simulated results of LARS-WG5 model, the average values of air temperature and precipitation will increase by 0.77, 0.88 and 0.78 0C and 2.1, 5.9 and 10.2 % for A1B, A2 and B1 scenarios, respectively.The results showed that average monthly precipitation will increase in October, December and February for three scenarios and decrease in March, April and May for A2 and B1 scenarios. Also, the total amount of net irrigation requirement of examined crops will increase between 2.6 to 28.2 mm for three future decades compared with baseline period