Impacts of Land Use Land Cover and Climate Change on Surface Water Balance Components of Gobele Watershed in Wabe Shebelle Basin, Ethiopia
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Date
2024-07
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Addis Ababa University
Abstract
Changes in land use land cover and climate are important global challenges due to the impact on water balance components. Climate change is caused by a change in greenhouse gas concentration due to natural and anthropogenic forcing. This study was conducted in Gobele watershed of the Wabe Shebelle River Basin, Ethiopia. It evaluated the individual and combined impacts of both climate change and LULC change on water balance components. Three historical periods (1990, 2005, and 2020) of Landsat satellite images of the study area were used for LULC analysis using ArcGIS. The Soil and Water Assessment Tool (SWAT) was utilized for the simulation of water balance parameters. Maximum likelihood classification was used to classify historical LULC, and the Cellular Automata-Markov Chain model in land change modeler was used to generate the future LULC forecast. The Statistical Downscaling Model (SDSM) was utilized to generate high-resolution future climatic data from well performed four climate models (ACCESS-CM2, MPI-ESM1-2-LR, ICHEC–EC–EARTH, and CanESM2) and their multi-model ensemble mean was used for impact assessment of climate and LULC change on water balance components. The hydrological response of the basin was evaluated using three scenarios: LULC change alone, climate change alone, and combined climate and LULC change. The future periods were divided into the midterm future (2040–2070) and the distant future (2071-2100). According to the CA-Markov chain model's projection of the LULC change, over the study period, agricultural land and settlement areas will increase while grassland/shrub land and forest land are expected to decline. The climate projection result indicates an increase in both Tmax and Tmin under SSP5.8.5 and SSP2-4.5 and SSP5-8.5 climate scenarios in the midterm (2040-2070) and distant future (2071-2100). Likewise, precipitation will show an increasing pattern in the basin. Under SSP5-8.5, evapotranspiration will increase more by climate change than by LULC change during the baseline period (1990-2020). Furthermore, both stream flow and water yield will increase under all scenarios. Moreover, the SWAT model performed satisfactorily in simulating discharge during the calibration and validation periods at the designated gauging station in the Gobele watershed with R2 and NSE values of 0.86, 0.76, and 0.91, 0.69, respectively. Thus, the results of this study provide valuable information to planners and policymakers for sustainable planning of water resources in the Gobele watershed in the face of climate and LULC change.
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Climate Change, LULC, Gobele Watershed, SWAT, Water Balance