Integrated Assessment of Land Use/Land Cover Dynamics and Climate Change Impacts on Watershed Hydrology in the Dawe Watershed, Ethiopia

Abstract

Freshwater sustainability is increasingly threatened by the impacts of land use/land cover (LULC) dynamics and climate changes, mainly in arid and semi-arid data-scarce watersheds of developing countries. This study assessed the separate and combined effects of predicted LULC dynamics and climate changes on the water resources in the Dawe watershed, Ethiopia. Future LULC was projected using a Cellular Automata (CA)-Markov model, while climate projections were derived from an ensemble of six CMIP6 Global Climate Models (GCMs) under the shared socioeconomic pathways (SSPs) SSP2–4.5 and SSP5–8.5. Hydrological responses were simulated using the Soil and Water Assessment Tool Plus (SWAT+) under nine scenarios (S0–S8), integrating projected LULC conditions (2024 and 2062) with mid-century (2024–2055) and late-century (2056–2085) climate projections. With Nash-Sutcliffe efficiency (NSE) and Kling-Gupta efficiency (KGE) values surpassing 0.8 during both calibration and validation, the model demonstrated strong performance. The simulations demonstrate a consistent increase in evapotranspiration (ET) under all scenarios, ranging from 13.0% under climate change alone (S1) to 23.4% under the combined LULC and climate change scenario (S8). In contrast, water yield (WY), surface runoff (SR), and groundwater recharge (GWR) will decline under all future scenarios, with the greatest reduction occurring under the combined effects of LULC and climate change. Under the worst-case scenario (S8: SSP5–8.5, 2062 LULC, and late-century climate), WY decreased by 34.5%, SR by 32.9%, and GWR by 23.2%. The continued land expansion and warming will alter watershed hydrology. Climate change is the main driver of hydrological shifts, amplified by LULC change. The worst impacts occur under combined SSP5–8.5 and 2062 LULC, so assessing drivers separately underestimates risks, underscoring the need for integrated modeling. These results highlight the necessity of integrated land and water resource management strategies to enhance water security and strengthen climate resilience.