Climate-induced changing environment in semidry lands: a statistical-based simulation approach in Qarasou Sub-basin of Karkheh River Basin

The present study was carried out to track the changing pattern of climate change at a watershed scale as a risk for the function of land systems. For this, the changing trend of the variables, including maximum and minimum temperature, and precipitation was simulated for the next 20 years using LARS-WG Software, version 5.0. The fifth version of the LARS developed based on the IPCC Fourth Assessment Report includes a total number of 15 models, among which six models (Gfcm21, Hadcm3, Incm, Ipcm4, Mpeh, and Ncccsm) are run with all of the three scenarios SRA2, SRA1B, and SRB1. In order to select the most appropriate model to simulate climate change in the Qarasou Watershed all of the 6 GCM models run with three above-mentioned scenarios were selected, whose average monthly output was compared with the observed data to determine which of the small-scale GCM models has better performance in simulating the meteorological data. The IPCM model was recognized as the best GCM model, in terms of the minimum error to downscale the meteorological data of the watershed. Once the simulation process completed, the climate change trends of the watershed were generated for the different variables, separately. According to the results, rainfall could be the primary climatic driver behind the decreased water supply for agricultural fields. Drier springs and autumns in the coming decades would potentially result in the increasing frequency of spring droughts.