Assessing The Impacts Of Land Use And Land Cover Change On Hydrology Of Baro Akobo River Basin, Ethiopia (Case Study: Upper Gilo Watershed)

Abstract

Land use land cover change is the global phenomenon that affects the watershed hydrological process and subject to changes causing the area to form impervious surface that affects the hydrological processes. This study was conducted to investigate the impact of land use land cover changes on hydrology of Upper Gilo Watershed located in the Baro Akobo River basin, southwest of Ethiopia. In this study SWAT model was selected as it applies distributed at required scale. Land use/Land Cover data, Hydrological data (stream flow) and meteorological data were obtained from Ethiopian Map Agency, Ministry of water Resources, Irrigation, and Electricity, National meteorological Service Agency respectively.. The result of sensitivity analysis has shown that the curve number (CN2), GWQMN, CH_K2, ALPHA_BF and SOL_Z are the top most sensitive parameters. The model was calibrated using stream flow data from 1993 to 2006 and validated from 2007 to 2014. The R2 and NSE values were used to examine model performance and the result indicates 0.91 and 0.82 to R2 and 0.77 and 0.61 to NSE during calibration and validation respectively. The classified Land use map of 1995, 2004 and 2013 which were obtained from Ethiopian Mapping Agency indicate that the cultivated land and settlement have expanded during the study period of 1995-2013 by 14% and 7% respectively and unlike that, forest and grass land were decreased by 11% and 4.7% respectively during the period. The effects of the land use land cover changes (1995-2013) have impacted on the stream flow of the watershed that changes the magnitude of surface runoff and sediment loading increased by 22% and 84% respectively but lateral flow, ground water flow, Aquifer recharge, and percolation capacity of the soil was decreased by 3.4%, 12.9% 8.4% and 14.6% respectively. During the study period, maximum annual surface runoff was contributed by sub-basin 31, 5 and 28 and the highest ground water was contributed by sub-basin 29, 25 and 25 for the period of 1995, 2004 and 2013 respectively. And maximum sediment load is contributed by sub-basin 22, 19 and 27.