Document Type : Research Paper
Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
Water Eng. Department, Civil Eng. Faculty, IAU University, Science and Research Branch, Tehran, Iran
University of Tehran
Department of Civil Engineering, Islamic Azad university
This study aimed to estimate groundwater recharge along with other balance components (runoff, evapotranspiration, and transpiration) in Hashtgerd plain, using the WetSpass-M distribution model in the conditions of climate change and land use in the next 30 years. To study the effects of climate change, the output of five models under four emission scenarios, i.e., RCP2.6, RCP4.5, RCP6, and RCP8.5 of the Fifth Report of the Intergovernmental Panel on Climate Change (IPPC) was utilized. The LARS-WG model was also used for the downscaling of the climatic data. Land-use mapping was performed using Landsat images in 1990, 2005, and 2020 processed in ENVI 5.3. The Markov chain method in TerrSet software was used to predict land-use changes for 2050. In the end, the effect of climate change and land use on underground water supply and other water balance components was simulated using the WetSpass-M distribution model for the period 2050-2020 and the effect of climate and land use scenarios was applied on it. The climate change results showed that the annual temperature will increase by 1.2 and 3.2 degrees Celsius until 2050 for the RCP2.6 and RCP8.5 scenarios, respectively, and the annual precipitation will decrease by 1.95% and 4.47% for both scenarios. The results of land use change show an increase of 105, 41, and 8 percent for residential, barren, and agricultural land, respectively, and a 94 percent decrease in pastures. With the increase of residential and barren uses and the decrease of pastureland, the permeability of the land will decrease, and as a result, the amount of surface discharge of the aquifer will decrease. Estimates, in general, showed that climate change has caused a decrease, land use change has increased the feeding of the aquifer in such a way that in the most critical scenario the amount of feeding will reach 220.6, and the balance of the aquifer will reach 115.9 million cubic meters per year. Because of climate and land use changes, the share of evaporation and transpiration has increased and the share of recharge and runoff from precipitation has decreased. In general, in the highlands due to more rainfall and in agricultural areas due to irrigation return water, the contribution of underground water supply has increased.