Application of SWAT Model to Assess the Impact of Land Use Changes on Daily and Monthly Streamflow of Subarnarekha River Basin

Abstract

Quantifying the impacts of land use change and land cover practices on the hydrological response of a watershed has been an area of interest for the hydrologists in recent years as this information could serve as a basis for developing sound watershed management interventions. The degree and type of land cover influences the rate of infiltration, runoff, and consequently the volumes of surface runoff and total sediment loads transported from a watershed.However very few studies in India, have used the physically based hydrological models along with the land use / land cover change conditions. Hence in this current work SWAT model has been used to assess the impact of LU/LC changes on daily and monthly streamflow of Subarnarekha River Basin. The SWAT model has been calibrated and validated against the daily and monthly streamflow for the gauging station of Govindpur in NH5 road situated along the Budhabalanga river. The results depict that SWAT model usually performs well in simulating runoff according to Nash-Sutcliffe efficiency (NSE), Coefficient of determination(R2) and Percentage bias (PBIAS) values. For daily stream flow the NSE, R2 and PBIAS values were 0.61, 0.64 and -12 during calibration period and 0.57, 0.60 and 14.2 during validation period respectively. For monthly stream flows the efficiency increased due to smoothening of curves and the NSE, R2 and PBIAS values were 0.76, 0.81 and 9.2 during calibration period and 0.79, 0.83 and 10.4 during validation period respectively. The results of the study indicated that the though land use patterns have changed resulting in increase in agricultural, barren and buildup land and decrease in forest cover leading to increase in runoff but changes have not occurred as significantly as the changes in annual streamflow. However the number of days of high intensity rainfall has increased over decade which along with the land use changes explains for the increase in streamflow.