The Effect of Land Use Change Scenarios on Runoff Using WETSPA Model with Parameter Allocation Approach in Karkhane Watershed, Hamedan Province

The most important human impact on the hydrological cycle of watershed is land use change. Improper management of land use increases the volume of runoff and the frequency of floods. The main purpose of this study is to investigate the effect of land use change on discharge outflow in Karkhane Watershed using the Parameter Allocation Approach. Then, utilizing the philosophy of a modelling framework proposed by Bahremand (2016), we show how calibration of most model parameters can be avoided by allocating or presetting these parameters utilizing knowledge gained from sensitivity analyses, field observations and a priori specifications as a part of a parameter allocation procedure. Evaluation of the WetSpa model performance using the Allocation Parameter Approach to simulate the daily hydrograph based on the Nash-Sutcliffe and Kling-Gupta showed that the values of these criteria are 60.18 percent and 76 percent respectively. Based on this efficiency criterion, the model in the parameter allocation approach has a good performance and shows consistency in the validation period. The results showed that land use change affects the runoff of the Karkhane watershed so that in the pessimistic scenario 2, the peak discharge has increased by 15.74% and in the optimistic scenario 3; the peak discharge has decreased by 11.33.