EVALUATION OF IMPACT OF CLIMATE CHANGE ON WATER RESOURCE AVAILABILITY ON ABAYA - CHAMO BASIN (THE CASE OF KULFO CATCHMENT)

Abstract

Nowadays the sign of climate change and its impact is revealing on different natural and man-made systems, in one or other ways. Accordingly, this impact is significant on the water resource system. This study mainly deals with evaluation of the climate change impact on the Kulfo catchmenet which is found in Rift valley. Statistical down Scaling Method (SDSM) was applied in order to downscale the climate variables at catchment level. SDSM was also used to downscale the present and future monthly precipitation and temperature from the UK Hadley center (HadCM3). Two future emission scenarios, A2 and B2 were considered for the three different periods (2030s, 2060s and 2080-2099). Downscaling was done to obtain finer resolution output from the GCM, so that it matches with the Kulfo catchment scale. The downscaled future climate showed that the mean daily minimum and maximum temperatures increase by up to 1.65/2.0 (2030s), 1.66/3.0 (2060s) and 1.66/3.6 (2080-2099) and annual precipitation also expected to increase up to 11% and 9% compared to base period for A2 and B2 scenarios. The output of downscaled data provided input rainfall and temperature data for the HEC-HMS model to estimate flow. A hydrological model, HEC-HMS was utilized to simulate the flow. The performance of the model was assessed through calibration and validation process and resulted R 2 =0.88 and NSE=0.87 during calibration and R 2= 0.9, NSE =0.866 during validation. The impact of climate change may also cause an increase in monthly mean flow up to 122% in the 2050s under A2 scenario and increase up to 100% in the 2090s under B2 scenario. Seasonal mean flow may show increase up to 106.6% Bega (JFD) and 42.8% Belg (SON) in season for 2050s and 2090s time periods respectively under B2 scenario. The increasing of seasonal mean flow in Bega (JFD) has its own contribution for occurrence of flooding in Kulfo Catchment. It is observed that there may be a net annual increase in mean annual flow volume in Kulfo River due to climate change.