Investigating the effects of land use on runoff generation using WetSpa model

The main objective of this research was assessing the effects of land use on runoff parameters such as total runoff, surface runoff and peak discharges at the Baghsalian watershed as a case study site. At first, land use maps of 1986 and 2012 were prepared using a synthetic method and landsat images. WetSpa model was applied to simulate daily runoff for 8 years (the first 5 years as calibration and the last 3 years as validation periods) with land use maps of years 1986 and 2012. Nash-Sutcliffe efficiency and aggregation measure was used to assess the accuracy of WetSpa model. The Nash-Sutcliffe efficiency was obtained 0.61% and 0.56% for the calibration and validation periods respectively. Moreover the aggregation measure criterion had values of 64% and 62% for the calibration and validation periods respectively. These criteria showed that the WetSpa model is a suitable model to simulate runoff in the Baghsalian watershed. As a result of land use changes from 1986 to 2012, simulated total runoff, surface runoff and peak discharges rates increased, while the rate of increase in surface runoff was higher than the rate of increase in total runoff. Total run off and surface run off for land use 1986 was 431.62 and 158.77 million m3 respectively and pick discharge was 27.45. These values for land use 2012 was 480.31, 182.86 and 30.94.