Impacts of Climate Change Under CMIP5 RCP Scenarios on the Hydrology of Lake Ziway Catchment, Central Rift Valley of Ethiopia

Abstract

This study predicts future runoff conditions under changing climate using multi model outputs from Coupled Model Intercomparison Project Phase 5 (CMIP5) over Lake Ziway Catchment in the Central Rift Valley of Ethiopia. Bias corrected precipitation, maximum and minimum temperature data from HadGEM2-ES, CSIRO-MK-3-6-0 and CCSM4 models under representative concentration pathways RCP8.5 and RCP4.5 were used as future climate. Soil and Water Assessment Tool (SWAT) is used to simulate the future inflows from Katar River and Meki River towards Lake Ziway. Maximum and minimum temperature increased under RCP8.5 and RCP4.5 scenarios however, precipitation showed reduction. The percentage change in monthly average precipitation showed extremes for HadGEM2-ES model which range between -51.19% during 2050s and +23.15% during 2080s under RCP8.5. The model output showed an annual decrement in runoff depth from Katar River up to 19.45% on RCP8.5 on CSIRO MK-3-6-0 model and maximum reduction was recorded on RCP4.5 at 17.49% for CCSM4 model. Meki River showed maximum annual reduction of 20.28% during 2080s on RCP8.5 for HadGEM2-ES model. Due to future reduction of River flow on the region optimal allocations for water use purposes at all levels of water resource development projects are crucial for future water planning and management.

Keywords: CMIP5; Lake Ziway Catchment; RCP; Runoff Estimation; SWAT model.