A pragmatic approach to the combined effect of climate change and water abstraction on Lake Ziway water balance, Ethiopia

Climate change and ongoing human activity have been threatening Ethiopia's Lake Ziway water balance. However, few studies have beenconducted to investigate the combined effects of climate change and water withdrawal on the Lake's water balance using climatechange and water withdrawal for irrigation datasets. We used High-resolution multiple climate models and Representative ConcentrationPathways (RCP) scenarios to assess the impact of climatic variables for two future periods: 2021-2050 and 2051-2080. Rainfall and temp-erature data biases were corrected using power transformation and variance scaling methods, respectively. The Hydrologiska Byr & aring;nsVattenbalansavdelning (HBV) hydrological model was employed to simulate surface inflow into Ziway Lake from the Meki and Katar sub-catchments. The FAO CROPWAT model was used to estimate the irrigation water demand of major crops grown in the study area. The resultsindicate that future temperatures and wet season runoff levels are expected to rise. Under the worst climate change scenario, climatechange and water withdrawal from the Lake for agriculture may cause the lake level to drop by 25 cm per year, resulting in a 10 km2surfacearea and 101 Mm3 volume reductions. Therefore, implementing preventive measures, proper planning and careful monitoring of lake wateruse is advised.