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Hydrological processes journal swat12/7/2023 ![]() Additionally, the reduction of surface water and groundwater could further exacerbate water stress in the downstream areas, affecting the availability of water resources in the catchment. These changes could lead to reduced water availability for crop production, which could be a chronic issue for subsistence agriculture. The changes in precipitation range from -11.2% to -14.3% under RCP4.5 and from -9.2% to -10.0% under RCP8.5, while the changes in temperature range from 1.7☌ to 2.5☌ under RCP4.5 and from 1.8☌ to 3.6☌ under RCP8.5. This decline is mainly due to the reduction in seasonal flows driven by climate change scenarios. The projected climate change shows a decrease in surface runoff, groundwater, and water yield, resulting in an overall decline of annual flow. Moreover, the increases in both maximum and minimum temperatures are higher for higher emission scenarios, indicating that RCP8.5 is warmer than RCP4.5. The results indicated that the ensemble mean of the six RCMs projects a decline in precipitation and an increase in temperature under both the RCP4.5 and RCP8.5 representative concentration pathways. The Soil and Water Assessment Tool (SWAT) model was used to assess the hydrological impacts of climate change on the catchment. The RCMs outputs were then bias corrected using distribution mapping to match observed precipitation and temperature. To achieve this objective, an ensemble mean of six regional climate models (RCMs) from the coordinated regional climate downscaling experiment (CORDEX)-Africa was used to simulate future climatic scenarios. This study investigated the impact of climate change on hydrological processes within the Gilgel Gibe catchment and aimed to determine the level of exposure of water resources to these changes, which is essential for future adaptability planning. This study suggests that the runoff generation method should be selected carefully based on the dominant flow pathway of a catchment, particularly for land use impact studies in the humid tropics.Climate change is a significant driver of water resource availability, affecting the magnitude of surface runoff, aquifer recharge, and river flows. Instead, lower evapotranspiration increased groundwater flow under the GA, and thus the steady low flow increased. Land use changes caused a reduction in infiltration rate, leading to higher high flow under the CN, while high flow did not change under the GA. These results are associated with differences in runoff generation mechanisms, where surface runoff contributes to total discharge to a much larger extent under the CN (43%) than the GA (4%). However, the two methods showed opposite changes in flow regimes: high flow increased (13%) under the CN while low flow increased (27%) under the GA. ![]() Simulations showed similar changes in the annual water budget: decreasing evaporation and increasing total discharge. The calibrated model, which performed well in simulating runoff under present land use condition in the Batanghari River Basin, Indonesia (42,960 km 2), was then used to simulate runoff using past and future land use scenarios. Hydrological responses due to deforestation in a humid tropical catchment were analyzed using two runoff generation methods available in the Soil Water Assessment Tool (SWAT) model: the Curve Number (CN) and the Green-Ampt (GA) methods.
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