Investigation of land use changes effects on daily stream flow in Nojian Watershed by Clue-s and WetSpa models

Land use and its fluctuations is one of the most important factors that affects on the natural cycle in the ecosystem. Land use changes cause change in watershed hydrological cycles, water balance between precipitation, evaporation, infiltration and runoff response. Understanding the relationship between land use changes and its factors and secondary effects on the hydrological regime provides the necessary information for planning of land use and sustainable management of natural resources. At first, land use maps related to years of 2000 and 2014 were prepared, then CLUE-s model was applied to simulate land use map of 2025. For simulating runoff, WetSpa model was employed to simulate daily runoff with land use maps related to years of 2000, 2014 and 2025. According to the results, the Nash-Sutcliffe evaluation criterion was calculated 68.26 % and 66.75 % for the calibration and validation periods, respectively. In addition, model Aggregate Measure (AM) was calculated 64 % and 54.15 % for the calibration and validation periods, respectively. Land use maps comparison showed, the main land use changes in Nojian Watershed was the conversion of forest and rangeland areas to agricultural lands .As a result of these changes the annual runoff volume, peak discharge, mean daily discharge increased to 16.20, 11.35 and 9.15 percent, respectively. Results of statistical analysis using paired t-test showed that land use change has effect on discharges in the study area at the level of 1%.