Simulation of Water Balance Components Using the SWAT Model in the Birr Watershed, Upper Blue Nile Basin

To manage water resources sustainably, understanding their quantity in spatial and temporal contexts is essential. Simulating Water Balance Components (WBCs) plays a crucial role. This study uses the Soil and Water Assessment Tool (SWAT) model to analyze water balance in the Birr Watershed of the Upper Blue Nile Basin, enhancing management strategies. By examining precipitation, evapotranspiration, surface runoff, and groundwater flow, the research provides insights into water availability and environmental impact. A comprehensive understanding of the water balance is crucial; however, past studies often overlooked long-term hydrological responses to climate and land use changes. To address this, the study uses datasets from 1990 to 2005, calibrating the model against streamflow records with the SUFI-2 algorithm, achieving high accuracy with NSE and R² values over 0.68. Findings indicate annual precipitation increased by 28.1%, from 457 mm in 1992 to 580 mm in 2006, then dropped to 264.88 mm in 2020, still 38% above initial levels, indicating significant climatic changes. Surface runoff surged by 55.7%, and groundwater flow grew by 42.7%, suggesting enhanced water availability but also potential risks for flooding and erosion. Evapotranspiration decreased slightly by 1.9%, likely due to varying climate factors. These hydrological changes affect agricultural productivity and ecosystem health, though uncertainties persist due to data constraints and insufficient integration of climate change assessments. Policymakers should implement integrated watershed management, promote sustainable land use, develop flood risk strategies, and strengthen hydrological data systems. Adaptive management strategies and cross-sector collaboration are essential for addressing climate change impacts and ensuring sustainable water resources for the basin's ecosystems. This study offers critical insights for effective policies aimed at sustainable hydrological management in vulnerable river basins.