Evaluating the impacts of wetland degradation on watershed hydrology: Implications for Eco-hydrological Restoration of Gojeb River sub basin, Ethiopia

Abstract

Combined human and climate pressures have led to significant changes in the spatial distribution and extent of wetlands, disrupting associated ecosystem services in Ethiopia. Nonetheless, the hydrological effects of wetland loss are still poorly understood across most of Ethiopia's river basins. This study aimed to analyse the long-term hydrological impacts of wetland loss in the Gojeb River sub-basin and evaluate wetland management interventions in restoring key eco-hydrological processes using the Soil and Water Assessment Tool (SWAT). Following the calibration and validation of historical streamflow records, the SWAT model was used to examine three primary scenarios: land use/land cover (LU/LC), wetland loss, and wetland restoration scenarios. The decline in wetland area between 2000 and 2024, led to a 2.3 % decline of groundwater recharge, while surface runoff and sediment yield increased by 8.5 % and 27.7 %, respectively. An extreme flow study revealed a flashier regime with greater peak flows at the same exceedance probability, implying a higher flood risk. Wetland degradation represented a significant trade-off, sacrificing short-term land gain for long-term vulnerability to flooding, erosion, and groundwater depletion. In contrast, wetland restoration has been shown to restore hydrological systems while decreasing sediment output. Wetland restoration, therefore, is an important strategy not only for ecological conservation but also for long-term water resource management, climate change adaptation, and local livelihood protection. The results highlight the importance of wetlands in maintaining hydrological stability, reducing the danger of erosion and floods, and supporting several other ecosystem services.