LAND USE LAND COVER AND CLIMATE CHANGES IMPACT ON STREAM FLOW AND SEDIMENT YIELD OF DURA WATERSHED, BLUE NILE BASIN, ETHIOPIA

Abstract

Land use land cover and climate changes are key factors controlling hydrological process in Dura watershed by modifying hydrological process. The watershed experienced soil erosion by the effect of intense rainfall which increases land use land cover and climate changes. The study uses SWAT model to evaluate the effects of land use land cover and future climate on stream flow and sediment yield of the watershed. LULCCs for the year of 1990, 2004 and 2019 were used to estimate stream flow and sediment yield. Those LULC changes were prepared using ERDAS Imagine 2015. The future climate was downloaded from CORDEX Africa and bias corrected using CMhyd software to Dura watershed Meteorological station points. The model performance was evaluated using coefficient of determination (R2 ) and Nash Sutcliff efficiency (NSE) with values greater than 0.80 for calibration and validation of stream flow and sediment yield during three different land use land cover maps. During the period from 1990 to 2019 dominantly cultivated land increases 8.94%, open woodland decreases 2.34% increases stream flow and sediment yield 4.6m3 /s and 9.5t/ ha/year respectively. Using simulated results of 2019 LULC map sediment vulnerable sub basins were identified. Future stream flow and sediment yield decrease from 24.1m3 /s to 7.21m3 /s (RCP4.5), 6.64m3 /s (RCP8.5) and 4.71t/ha to 1.41t/ha (RCP4.5), 0.92t/ha (RCP8.5) respectively using MIROC5 at the end of 2090. Similarly, using CSIRO_Mk3.6.0 stream flow and sediment yield decreased from 24.1m3 /s to 14.03m3 /s (RCP4.5), 13.98m3 /s (RCP8.5) and 4.71t/ha to 2.5t/ha (RCP4.5), 2.41t/ha (RCP8.5) respectively at the end of 2090.