ASSESSMENT OF CLIMATE AND LAND USE LAND COVER CHANGE IMPACTS ON HYDROLOGICAL PROCESS OF EYELA WATERSHED, NORTHERN ETHIOPIA

Hydrological processes within watersheds are critically influenced by the combined effects of land use/land cover (LULC) change and climate change, increasing vulnerability to extreme events like floods and droughts. This study investigates the individual and combined impacts of LULC and climate change on the hydrological regime of the Eyela Watershed. The analysis utilized remote sensing imagery, observed hydro-climatic data, and climate projections from the Coupled Model Intercomparison Project Phase 6 (CMIP-6) under different Shared Socioeconomic Pathways (SSPs) scenarios. Historical climate data and multi-temporal LULC maps were used to assess trends. The Soil and Water Assessment Tool (SWAT) hydrological model, integrated with GIS, was employed for simulation, demonstrating very good performance during calibration (R²=0.88, NSE=0.87) and validation (R²=0.85, NSE=0.84). Analysis of LULC change from 2014 to 2024 revealed a significant expansion of agricultural land (from 51.26% to 58.52%) and urban area (from 6.93% to 9.66%), accompanied by a decline in forest, bare land, and water bodies. The hydrological impact of this LULC from 2014 to 2024 showed an increase in stream flow of the watershed from 27.66m³/s to 34.26 m³/s. Climate projections indicated a future increase in stream flow. Under the SSP-4.5 scenario, the average monthly stream flow is projected to rises by 49.61 m³/s in the Near Future (NF: 2024-2060) and 47.33 m³/s in the Mid Future (MF: 2060-2100). A more pronounced increase is projected under SSP-8.5, with increment of 69.40 m³/s (NF) and (52.26) m³/s (MF). The results demonstrate that LULC change has a more immediate and substantial impact on the water balance than climate change in this watershed. These findings highlight the necessity for integrated water resource management strategies that address both anthropogenic LULC changes and climatic influences to ensure the watershed's long-term resilience and sustainability.