Modeling the Impacts of the Changing Land Use and Land Cover and Climate on Stream Flow in the Upper Awash Subbasin, Ethiopia

Understanding the combined influence of land use/land cover (LULC) and climate change on watershed hydrology is essential for sustainable water resource management in rapidly changing environments. This study evaluated the isolated and combined impacts of LULC and climate change on streamflow and basin water balance in the Upper Awash subbasin (UASB), Ethiopia, using geographic information system (GIS), remote sensing techniques, and the soil and water assessment tool (SWAT) model. LULC maps for 1990, 2005, and 2020 were prepared using ERDAS Imagine 2015 through supervised classification with a maximum likelihood algorithm. The results revealed substantial expansion of agricultural land from 64.16% in 1990 to 82% in 2020 and urban/settlement areas from 0.93% to 4.52%, while forest, shrubland, and grassland declined significantly. The SWAT model was calibrated (2002–2006) and validated (2007–2010) at the Hombole gauging station, yielding reliable prediction with R 2 values of 0.83 and 0.77, Nash–Sutcliffe efficiency (NSE) values of 0.78 and 0.73, and percent bias (PBIAS) values of 11.35 and 8.9, respectively. To assess the effects of LULC and climate change, three periods of climate data (1989–1999, 2000–2010, and 2011–2019) and corresponding LULC maps were analyzed. Scenario analysis showed that LULC change alone increased average monthly streamflow by 4.8% due to increased surface runoff associated with agricultural and settlement expansion. In contrast, climate change reduced streamflow by 1.26% as a result of declining rainfall (12.1%) and increasing potential evapotranspiration (PET, 4.1%). Under the combined LULC and climate‐change scenario, streamflow increased by 4.6%, indicating that the hydrological influence of LULC change outweighed climate effects during the study period. However, combined impacts reduced total basin water yield by 35.9%, highlighting increasing hydrological stress and declining water availability. These insights are useful to mitigate hazards, such as floods and droughts in a region facing rapid population growth and climate variability, ensuring the basin’s resilience and sustainable development.