Application of CORDEX-AFRICA and NEX-GDDP datasets for hydrologic projections under climate change in Lake Ziway sub-basin, Ethiopia

Abstract

Study regionLake Ziway sub-basin, Central Rift Valley basin, Ethiopia. Study focusThis study evaluated the applicability of the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) and the Coordinated Regional Downscaling Experiment (CORDEX-AFRICA) datasets for climate change impact assessment. It also evaluated the hydrologic impact of climate change in the sub-basin. The hydrologic model Soil and Water Assessment Tool (SWAT) was forced with the climate datasets to simulate the reference and future period streamflows under RCP 4.5 and RCP 8.5 scenarios. The seasonality and volumetric deviations of the average annual streamflows simulated using the climate models were used as criteria for selecting members of the ensemble. New hydrological insights for the regionAll the climate models in the bias-corrected NEX-GDDP datasets failed to satisfy the criteria. The ensemble average annual streamflows, simulated using the CORDEX-AFRICA dataset, are expected to increase towards the end of the century under both the climate scenarios. However, the ensemble average dry season streamflows are projected to decrease during the mid- and end-periods of the century. The expected decreases in streamflows during the dry and pre-wet seasons, along with excessive abstractions of water from Lake Ziway, would exacerbate water scarcity in the basin. Approaches need to be developed to capture the increase in water availability during the wet season to alleviate water scarcity during the dry season.