Investigation the effects of land use change on surface runoff using Remote sensing and SWAT model

Land-use and land-cover change, especially when caused by human activities, is one of the most important components of global environmental change. Land use is one of the most important issues in hydrological modeling to assess the effects of land use changes on water resources. Study all factors that souled affect the runoff can be difficult and is very complex and requires the use of new techniques and models to examine the effect of different factors. Land use change is an important characteristic that should influence erosion, evaporation, transpiration and runoff. Nowadays, preparing land use maps via satellite data and quantitative methods are very common in remote sensing science researchers. These techniques were widely used by scientists in the past two decades. The main aim of this study was to investigate the potential effects of land use change on surface runoff production using SWAT model. The study area named BeheshtAbad, located in the North and North East of Karoon watershed. For this study, 8 land use maps were created for the period of 1987-2013 using Landsat satellite image. In this study, runoff was simulated for 1984-1989 based on 1987 land use by SWAT model. For calibration and validation of the model, SUFI-2 algorithm was used in SWAT-CUP software. Statistical results of the model calibration and validation showed an acceptable accuracy in runoff simulating. In order to evaluate the effect of land use change on runoff potential, two type of land use were applied. Runoff for 1999 to 2011 period was simulated based on 1987 and 2013 land use maps. For 1999 to2011 period, no acceptable accuracy for estimated runoff was obtained when land use maps of 1987 was applied, whereas accuracy of the calibration and validation was increase when 2013 land use was applied. When 2013 land use was applied, the observation runoff was in the range of the uncertainty band PPU95 % of SWAT model. According to results, the amount of surface runoff has been increased in the recent years. It is difficult to study all factors that should affect the runoff. Using new techniques and models was required to examine the effect of different factors on runoff amount. The results of this study indicated that if the input data is properly prepared for SWAT model, this model should have a good performance to estimate of runoff. Land use mapping in accordance with the actual conditions of the region can have the greatest impact in the accuracy of the model.