IMPACT OF CLIMATE AND LAND USES LAND COVER CHANGE ON SURFACE HYDROLOGY IN UPPER BARO WATERSHED, BARO-AKOBO RIVER BASIN, ETHIOPIA

Abstract

Changes in climate and land use/land cover (CULL) can have a major impact on hydrological regimes. it's crucial to gain a thorough understanding of these factors and quantify their distinct effects to properly manage water resources. Therefore, the main objective of this study was to evaluate the climate and LULC changes impact on surface hydrology of the Upper Baro watershed. The analysis in this study encompasses investigating the changes in historical land-use patterns, evaluating the individual and combined impacts of LULL and climate change on hydrology, and identifying the dominant factors. The land use and land cover data for the years 1994 and 2009 were obtained from Landsat images and processed using ERDAS IMAGINE 2015 software. The impact of these changes was assessed using a semi-distributed physically-based hydrological model called the Soil and Water Assessment Tool (SWAT), which was used within the ArcGIS interface. The coordinated regional climate downscaling experiment (CORDEX)- Africa data outputs of RCMs derived from HadGEM2-ES under intermediate and high emission scenarios were analyzed from 2030 up to 2050 to further evaluate the the future impact of climate changes .The study found that the highest increase in LULC were observed in agriculture and urban areas, with an increase of 8.75% and 4.58%, respectively. However, the highest decrease were observed in woodland and forest lands, which saw a reduction of 6.29% and 4.08%, respectively. The calibration and validation of the study were conducted using SWAT CUP and evaluated using three model efficiency measures: R 2 , NSE, and PIAS. The calibration measures showed values of 0.89, 0.89, and 1.3%, for R2 , NSE, and PIAS respectively, while the validation measures showed values of 0.74, 0.72, and -7.2%, respectively. These results indicate a good agreement between the observed and simulated streamflow. Based on the hydrologic model simulations, it has been revealed that the individual LULC change show the increase of both surface runoff (Qs) and evapotranspiration(ET) by 11.97% and 0.51% respectively. On other hand under climate analysis, Qs was decrease by - 14.59% and ET increase by by 4.7%. when we consider impact of change of both factor, Qs was decreased by -5.39% and ET was increased by 5.34%.These findings emphasized the significance of climate change in the Upper Baro watershed. According to the future precipitation and temperature projections, it has been revealed that the Upper Baro watershed will experience a decrease in rainfall by 9.5% and 12. 17 % under RCP4.5 and RCP8.5 respectively and an increase in temperatures by 1.87°C and 2.29°C under RCP4.5 and RCP8.5 respectively . This will result in a decline of all hydrological components (surface runoff and evapotranspiration) under both RCP4.5 and RCP8.5 scenarios.The study's overall findings suggest that the effects of LULC and climate change may alter the hydrological regimes over the entire watershed. Effective land and water management practices are necessary to mitigate this impact