Investigating the Effects of Greenhouse Gases Emission on Supply and Demand of Irrigation Water in Watersheds of Qazvin Province

Increasing the emissions of greenhouse gases is among the factors affected the speed of occurrence of climate change during recent decades. In present study, first using time series data of 2006-2012 and RCM-PRECIS simulation model, the impacts of greenhouse gases emission on climatic variables of temperature and precipitation was investigated under different scenarios in watersheds of Qazvin Province. Then, the ordinary least squares (OLS) method and regression analysis were used to assess the impacts of climatic variables of temperature and precipitation on the selected products yield. Afterwards,considering the results of regression analysis in positive mathematical programing (PMP) model, the amount of the created variation in supply and demand of irrigation water and agricultural output in watersheds of Qazvin Province was investigated. The results showed that emission of greenhouse gases under scenarios A, B, and C affects the climatic variables of temperature and precipitation about 0.43 to 1.27 °C and -14.1 to 1.31 mm respectively. This case changes the selected products yield in the surface of each river basin of Qazvin Province. Change in yield affects acreage of agricultural crops by about -10.51 to 3.17 percent, the amount of irrigation water supply by about -10.4 to 1.64 percent, and the amount of irrigation water demand by about 1.60 to 7.35 percent. Moreover, the results showed that maximum and minimum decrease in the gap between supply and demand of irrigation water happens in Kharroud and Shahroud watersheds by about 9.20 and 1.82 percent respectively. With estimating the gap between demand and supply of irrigation water, one can adopt the appropriate decisions for sustainable water resources in watersheds of Qazvin Province.