Impact of climate change on the water resources of Awash River Basin, Ethiopia

Abstract

An attempt was made to investigate the sensitivity of water resources to climate change in the Awash River Basin in Ethiopia. The climate of the basin varies from humid subtropical to arid. The basin was divided into 3 subcatchments for better resolution in calibration and simulation. Station-based meteorological data were processed to obtain areal averages necessary for the simulation. Different sets of temperature and rainfall scenarios were developed using GCM (both transient and CO2 doubling) and incremental scenarios. The IIASA integrated water balance model (WatBal) was used to estimate runoff under a changed climate. The model represents the water balance among surface outflow, subsurface outflow, and evapotranspiration. The model was calibrated using a 10 yr period (1971 to 1980), validated with the next 6 yr period (1981 to 1986), and then applied for different climate scenarios. Results of the impact assessment over the basin showed a projected decrease in runoff, which ranged from -10 to -34%, with doubling of CO2 and transient scenarios of CO2 increase (GFD3, CCCM, GF01). Sensitivity analysis based on incremental scenarios showed that a drier and warmer climate change scenario results in reduced runoff.