Hydrological responses to future climate and land use/land cover change in the Upper Blue Nile Basin, Ethiopia: A systematic review

This is the authors' abstract. We don't add key points for this paper.

The hydrological regimes of the Upper Blue Nile Basin (UBNB) are undergoing rapid transformation under the combined influence of climate change and land use/land cover dynamics. This review aims to synthesize the hydrological responses of the UBNB to projected climate change and land use/land cover alteration, both in isolation and in combination. The reviewed studies span different sub-basins, watersheds, climate scenarios, modelling approaches, and future time horizons, resulting in considerable variability in reported hydrological responses. Nevertheless, study-specific projections in the UBNB indicate future reductions in dry-season flow of approximately 35-50% under specific climate scenarios and future periods, alongside increases in wet-season peak flows. Land use/land cover change alone is associated with a projected 5–24% future increase in Surface Runoff (SR) and reduced baseflow based on the reviewed studies. The combined effects of climate change and land use/land cover are generally more pronounced than their isolated impacts, resulting in a more runoff-dominated hydrological regime. Across the reviewed studies in the UBNB, the combined effects are reported to result in a future increase in water yield (up to 30.4%), SR (up to 27.8%), sediment yield (up to 41.01%), and a decline in groundwater flow (up to 15.30%). The findings highlight the need for proactive and integrated watershed management, including sustainable land-use planning, soil and water conservation, reforestation, and climate-resilient infrastructure to safeguard water security in the UBNB. They also emphasize the importance of considering both climate change and land use/land cover impacts in water resource planning. Future research should reduce model uncertainties and use downscaled Global Climate Model data to guide site-specific adaptive strategies.