Impact of climate change on the streamflow of the Arjo-Didessa catchment under RCP scenarios

Wudeneh Temesgen Bekele,Tom Rientjes,Alemseged Tamiru Haile

doi:10.2166/wcc.2021.307

Abstract

AbstractIn this study, the impact of climate change on the streamflow of the Arjo-Didessa catchment, Upper Blue Nile basin, is evaluated. We used the outputs of four climate models for two representative concentration pathway (RCP) climate scenarios, which are RCP 4.5 and RCP 8.5. Streamflow simulation was done by using the HEC-HMS rainfall-runoff model, which was satisfactorily calibrated and validated for the study area. For the historic period (1971–2000), all climate models significantly underestimated the observed rainfall amount for the rainy season. We therefore bias-corrected the climate data before using them as input for the rainfall-runoff model. The results of the four climate models for the period 2041 to 2070 show that annual rainfall is likely to decrease by 0.36 to 21% under RCP 4.5. The projected increases in minimum and maximum temperature will lead to an increase in annual evapotranspiration by 3 to 7%, which will likely contribute to decreasing the annual flows of Arjo-Didessa by 1 to 3%. Our results show that the impact is season dependent, with an increased streamflow in the main rainy season but a decreased flow in the short rainy season and the dry seasons. The magnitudes of projected changes are more pronounced under RCP 8.5 than under RCP 4.5.

Highlights

The fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) indicates that rainfall over Eastern Africa has decreased between March and June in the last three decades, while there has been an increase in temperature over East Africa since the beginning of the 1980s
Simulated streamflow volume for the study area is most sensitive to the constant rate (CR) and moderately sensitive to the base flow (BF) parameter
We evaluated the impact of climate change on the streamflow of the Arjo-Didessa catchment for the medium-future period 2041–2070 under the representative concentration pathway (RCP) 4.5 and RCP 8.5 scenarios

Summary

Introduction

The fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) indicates that rainfall over Eastern Africa has decreased between March and June in the last three decades, while there has been an increase in temperature over East Africa since the beginning of the 1980s. Climate projections indicate that there will be a likely increase in rainfall amount and extreme rainfall in the region by the end of the 21st century. There will be higher rates of evaporation in Ethiopia due to warming over the country Such changes are expected to impact the economy of East African countries, including Ethiopia, by high climate sensitivity (Change ). Beyene et al ( ) and Elshamy et al ( ) reported that the flow of UBN is likely to decline by the end of the century. The magnitude of floods in the UBN is expected to be more severe (Kim & Kaluarachchi ; Nawaz et al ), while the direction of projected changes of the dry season flows of the UBN basin is not clear (Taye et al ; Enyew et al )

Methods

Results

Conclusion