MODELING SUSTAINABILITY OF SURFACE WATER RESOURCES INTEGRATING IPCC CLIMATE CHANGE SCENARIO AND WEAP: GIDABO CATCHMENT, RIFT VALLEY BASIN, ETHIOPIA

Abstract

Improper water allocation and ensuing conflicts are of serious concern for almost all countries around the world. Climate change is anticipated to aggravate the already existing water stresses initiating the enhancement of water use and allocation efficiency against various competing demands. The aim of this study is evaluating the existing and future surface water resources potential and demand in Gidabo catchment under changing climate and water resources development scenarios. The demographic, irrigation and hydro-meteorological data in the catchment was collected from different sources and future climate scenarios under RCP 4.5 and RCP 8.5 have been used at their optimum level to find a better and more precise solution. The power transformation and linear scaling have been used to remove the biases in precipitation and temperature data. The baseline and future water resources potential of the catchment was estimated using HEC-HMS model. The mean annual water availability and demand for baseline period to be 619.87 MCM and 78.18 MCM respectively. The trends of projected climate variables have shown positive change for both temperature and precipitation under both RCP 4.5 and RCP 8.5 emission scenarios. The mean annual future surface water resources potential of the catchment was estimated as 682.77 MCM and 621.11 MCM under RCP 4.5 and RCP 8.5 respectively. The WEAP model considering three future demand scenarios namely; population growth and increase in domestic water consumption, exploitation of pre-identified irrigation and irrigation expansion was developed based on different sets of assumptions. The mean annual future water demand in the near future year of 2021-2040 had shown an absolute increase ranging from 100 MCM to 208 MCM; irrigation expansions being the highest water demanding scenario. The study depicted that all the demands are fully met in baseline and future period except for irrigation and industrial demand in future period during dry months throughout January to March. Such a scarcity can be merely met storing excess water available during the rainy season for further use during dry months