Abstract:
Climatic and land use/land cover (LU/LC) changes exert significant influences on hydrological
processes across various spatial and temporal scales. The Gilgel Gibe catchment in southwest
Ethiopia serves as a crucial water source for diverse socio-economic and environmental
purposes. However, this catchment is undergoing rapid land use/land cover (LU/LC) as well
as climatic changes, which are profoundly affecting its hydrological processes and water
resources. This study investigated the combined effects of LU/LC and climate change on the
hydrological processes within the Gilgel Gibe catchment. The Soil and Water Assessment Tool
(SWAT) model was employed to simulate hydrological responses under three LU/LC
scenarios (2021 baseline, 2039, and 2057) and two Representative Concentration Pathways
(RCPs) for climate change (4.5 and 8.5) from 1991 to 2099. The interpretation and
classification of Landsat imagery, along with the results from field observations, have revealed
substantial LU/LC alterations between 1991 and 2021. There has been an expansion of
cultivated land and built-up areas, while forest cover, grazing land, and shrubland have
declined. Factors such as human population growth, agricultural land expansion, built-up area
expansion, land degradation, deforestation and inadequate conservation practices are driving
these changes. Both LU/LC and climate change markedly influence the catchment’s
hydrological processes. Land use/land cover change projections showed an increase in surface
runoff (2.02%-4.09%) and water yield (2.62%-3.23%), but a decrease in groundwater recharge
(0.09%-0.63%) relative to the baseline. Climate change is anticipated to exert a more
substantial impact, with the most pronounced reductions in surface runoff, groundwater
recharge, and water yield expected under the RCP8.5 scenario. The combined effects of LU/LC
and climate change appear to be additive, intensifying these trends and posing potential risks
to water availability and the sustainability of resources in the catchment. This indicates the
Gilgel Gibe catchment’s vulnerability to both LU/LC and climate change, with anticipated
alterations to the hydrological processes. This study emphasizes the pressing need for a
coordinated approach to address the combined effects of LU/LC changes and climate change
within the Gilgel Gibe Catchment. As such, policymakers and stakeholders ought to focus on
enhancing agricultural productivity through improved inputs and conservation practices,
developing alternative income sources for sustainable livelihoods, and strengtheningstakeholders in sustainable management practices and establishing climate-resilient
environment is vital. Future research should evaluate the impacts of land degradation on
hydrology and sedimentation, as well as the role of vegetation in soil conservation. These
activities are critical for the environmental sustainability of the catchment and the welfare of
the communities that rely on it. Collective efforts are essential to ensure the catchment’s
environmental sustainability and the prosperity of the communities it supports
ecosystem conservation via reforestation and afforestation practices. Moreover, e
