Using SWAT Model to Investigate the Impact of Rangeland Management Practices on Water Conservation (Case Study: Gorganroud Watershed, Golestan, Iran

Abstract. Hydrological response of a watershed is a comprehensive symbol of environmental conditions and characteristics of the basin. Vegetation is one of the main factors in water resources status, erosion, and sediment of a watershed. Rangelands of Golestan province, Iran due to the geographical location, climate, and destruction of these resources as well as drastic land use changes from forests, and rangelands to agricultural lands have a high potential of run-off. Therefore, in the present study in order to determine the best management of the rangelands, we developed a rangeland improvement model using the Soil and Water Assessment Tool (SWAT) in the Gorganroud Watershed, Golestan, Iran. Calibration and validation of model were performed using Sequential Uncertainty Fitting Program (SUFI-2) in the eco-hydrological model of SWAT. Simulating the run-off in the studied hydrometric stations, the results showed that this model performed well for the study area (P-factor 0.6-0.9; R-factor 0.85-1.5). As well, four range improvement scenarios (mechanical, biological, biomechanical and livestock grazing management) were defined in this study. On average, by applying mechanical, biological, biomechanical, and grazing management scenarios, runoff was reduced to 13.5%, 11%, 20.7% and 12.5%, respectively in comparison with the actual runoff. According to the obtained results, the biomechanical scenario was identified as the best one in reducing the runoff and water conserve in poor and moderate rangelands