Investigating the impact of land use and land cover changes on Muga watershed

Abstract

Hydrologic modeling and water resources management studies are closely related to the spatial processes of the hydrologic cycle. This cycle is affected by several factors like climate and land use / land cover changes. Deforestation is a day to day activity of the people living in the Muga watershed, the watershed in this study facing high erosion by the effects of intense rainfall of the watershed which aggravates the land cover change of the watershed. Population pressure, lake of awareness and weak management are considered the major cause for the deforestation and degradation of natural resources .This study is mainly focusing on the assessment of the impacts of the land use / land cover changes on the stream flow of Muga watershed, by Gis interface soil and water assessment tool (SWAT). For this study SWAT Simulation is used in identifying the most vulnerable sub basins to the stream flow and sediment load changes of Muga watershed. The model was calibrated and validated using the observed Stream flow of Muga River at a gauging station near Dejen. Sensitivity analysis shows curve number CN, GW_DELAY and SOL_AWC are the top three sensitive parameters. The model was calibrated using stream flow data from 1993 to1998, validated from 1999 to 2002 and from 1990-1992 used for warm up period. The R2 and NSE values were used to examine model performance and the result indicates 0.88 and 0.90 to R2 and 0.86 and 0.89 to NSE during calibration and validation respectively. The result of land use /land cover change showed that the land use / land cover changes have significant effects on infiltration rates, runoff production, water yield, sediment loading, and evapotranspiration and water retention capacity of the soil. The result of this analysis indicated that the mean monthly stream flow for wet months had increased by 17.75 m3 /s while the dry season decreased by 12.76m3 /s during the 1995-2013 period due to the land use and land cover change. The highest annual surface runoff was attributed by sub basin 5 whereas sub basin 6 contributes the highest ground water respectively for 1995, 2003 and 2013 land cover maps. In terms of sediment yield, sub basin 1 contributes a maximum load for the study periods.