IMPACT OF CLIMATE CHANGE ON AGRICULTURAL WATER DEMAND: THE CASE OF BILATE RIVER CATCHMENT

Abstract

Climate change has impact on agricultural water demand by affecting the different climate variables such as temperature and rainfall. This study was carried out to detect the impact of the climate change on agricultural water demand under different time horizon to prevent vulnerability to climate change at Lower Bilate River sub-basin. The data used in this study were collected from National Meteorology Agency of Ethiopia, Ministry of Water, Irrigation and Electricity. Simulated climate data were obtained with using single climate model ICHEC-EC EARTH, Precipitation and temperature time series of historical and projected time period. The scenarios used were from the Eth_CORDEX_Grids archive based on RCP4.5 and RCP8.5 Scenarios. The trend analysis for the last 32 years, indicated that the impact of the climate change to changes in long-term maximum and minimum temperature is increased by 0.0395o c and 0.1380 c respectively and changes in precipitation is by the factor of the -0.83, the prediction analysis indicates that precipitation at the study area will be -35.71% and -40.18% for the year 2048 and 2080 respectively from RCP4.5 Scenarios. Whereas, based on RCP8.5 Scenarios the change in the same order will be -48.90% and -60.11%. As a result the change is expected in agricultural water demand for the selected crops at specific study area. The average irrigated agriculture water demand of selected crops Tobacco and cotton are found to be 19.01Mm3. However, this value is not kept constant as a result of the change in climate that for future time period (2017-2048) and (2049-2080) found to be 24.01Mm3 and 25.01Mm3 respectively for RCP4.5, and in case of RCP8.5 is found to be 25.33Mm3 and 28.36Mm3 respectively. Whereas, the Rain fed agriculture water demand for the crops maize and haricot bean are estimated 87.98Mm3 at the study area. As a result, the change in climate computed as 86.65Mm3 and 104.28Mm3 for the period of 2048 and 2080 respectively for RCP4.5 Scenarios, whereas based on RCP8.5 Scenarios the change will be 100.39Mm3 and 125.42Mm3 respectively