Land Use/Cover Change Impacts on Hydrology Using SWAT Model on Borkena Watershed, Ethiopia

Land use/cover change has been a key research priority throughout the planet with multi-directional impacts on both human and natural systems. The changes in land use/cover have affected the surface hydrology and altered the hydrological cycle (Skaggs et al. in Agric Water Manag 86(1-2), 140-149, 2006). This study is concentrated on assessing the effect of land use/cover change on the hydrology of the Borkena watershed. The study was examined by Arc GIS10.3. SWAT model used with GIS to assess the impact of land use and land cover change on streamflow. For this study, SWAT Calibration and Uncertainty Procedures (SWAT-CUP) was selected to do sensitivity analysis, calibration, and validation. The temporal change in land use/cover was analyzed for the years 1986, 2000, and 2011. Analysis of land cover changes showed that agricultural land increased from 18.64 to 49.75%, still as urban areas from 1.16 to 10.17% between 1986 and 2011. While shrubland decreased from 10.97 to 8.29%, forest decreases focused 7.25 to 23.24%, grassland decreased from 10.72 to 8.45%, and wetland decreased from 1.26 to 0.08% between 1986 and 2011 respectively. The result of calibration and validation for the monthly flow showed that there is a good relationship between measured and simulated streamflow with the model performance evaluation; for calibration, the coefficient of determination is 0.93 and Nash Sutcliffe efficiency is 0.89 and for validation, the coefficient of determination is 0.98 and Nash Sutcliffe efficiency is 0.95. Within the calibration and validation period, there is a good correlation between rainfall and surface runoff in the watershed with the percentage of fit greater than 90%. The annual surface runoff for the 1986, 2000, and 2011 land use/cover periods is 152.37 mm, 193.44 mm, and 198.8 mm, respectively. The model results showed that the hydrology characteristics changed because of land use/cover changes during the study periods. This study only focuses on the impact of land use/cover change on streamflow components such as surface runoff. The study plays a crucial role to create the power of planners to implement sound policies to reduce undesirable land use and land cover impacts on streamflow.