Evaluation of Climate Change Impact on Streamflow (A Case Study of Dabus River,Abay Basin Ethiopia) Using CORDEX-RCP and SWAT Model

Bernabas Tesfaye

doi:10.7176/cer/12-12-02

Abstract

Climate change is becoming one of the most debating and threatening issues in terms of global context which alter regional hydrologic conditions and results in a variety of impacts on water resource systems. The aim of this study is to assess the impact of climate change on the stream flow of Dabus Sub-basin which located in upper Blue Nile Basin of Ethiopia. The CORDEX RCM downscaled and bias corrected were used for the climate projection. To estimate the level of impact of climate change, climate change scenarios of precipitation and temperature were divided into three time windows of 25 years as the whole from (2025-2099). Soil and water assessment Tool (SWAT) was calibrated and validated for stream flow simulation using SWAT-CUP with a method of SUFI2. The results showed that the value of calibration and validation reveals a good agreement with R 2 =0.84 during calibration and R 2 =0.82 during validation whereas NSE= 0.75 during calibration and NSE=0.72 during validation. The maximum and minimum temperatures increase for the three time horizons under both scenarios with largest increase under RCP8.5. The largest increase of mean annual maximum temperature under RCP4.5 is 1.31 o C while under RCP8.5 that increase by 3.097 o C in future periods of (2075-2099). Similarly, The largest increase of annual minimum temperature under RCP4.5 scenario by 1.28 o C while 1.42 o C under RCP8.5 in future periods of (2075-2099). Compared to the base line period the total annual precipitation decrease for the three time horizons under both scenarios. A decrease of mean annual precipitation under RCP4.5 are 12.8% , 18.26% and 21.27% while under RCP8.5, it show decrease by 13.76%, 14.87% and 13.6% in the future periods of (2025–2049), (2050-2074)and (2075-2099) respectively. The stream flow projections are made in the future with two emission scenarios of RCP4.5 and RCP8.5, the study show that an average annual decrease in the stream flow up to 11.97% for RCP4.5 and up to 13.37% for RCP8.5 in the next 75 years. Keywords: Dabus Sub basin; SWAT; RCP Scenario; CORDEX RCM ; Climate Change DOI: 10.7176/CER/12-12-02 Publication date: December 31 st 2020

Highlights

Climate change refers to any systematic change in the long-term records of climate elements sustained over various decades or longer time periods
Ethiopia is heavily dependent on a rain-fed agriculture, and its geographical location and topography in combination with low adaptive capacity entail a high vulnerability to adverse impacts of climate change (Yirga, 2007)
Evaluating future precipitation and temperature change result in the study area show the fluctuation in extreme hydrological events that may happen in the future and helps to convey valuable information on the future projected climate change variables in Dabus Sub basin to design a policy strategies to incorporating the appropriate adaptations and mitigation measures to preserve water resources in light of future climate change scenarios in the basin

Summary

Introduction

Climate change refers to any systematic change in the long-term records of climate elements (such as temperature, pressure, or winds) sustained over various decades or longer time periods. This study tried to investigate how changes in climate element might translate into changes in stream flow in the Dabus Sub basin in particular.

Objectives

Results

Conclusion