THE IMPACT OF CLIMATE CHANGE ON CROP WATER REQUIREMENT OF MAIZE AT UPPER BILATE WATERSHED, RIFT VALLEY RIVER BASIN, ETHIOPIA

Abstract

Climate change is a topic of discussion worldwide, including in Ethiopia. Ethiopia is one of the country’s most vulnerable to the impacts of climate variability and change on agriculture. This study investigates how crop water requirements under climate changes scenarios for maize crop in upper bilate catchment. The observed daily climate data were obtained from the National Meteorology Agency (NMA) while Seventeen GCMs from the MarkSim-GCM were used for RCP 4.5 and 8.5 scenarios for future projection. The onset, cessation of the growing season, and length of the growing period were analyzed using instat software version 3.37 after quality control of the rainfall data. Mann-Kendall's trend detection and Sen.’s slope estimator were used by XLSTAT software to evaluate the trends of projection and to detect changes. CROPWAT model window 8.0 was used to estimate present and future crop water requirement of Maize. The coefficient variation (CV) of all stations of Belg rainfall ranges between 25.3% and 34.6%, whereas the Kiremt CV ranges from 13.6% to 33.6%. The mean onset of the Kiremt was found to occur during the first dekad of June and ended during the second dekad of September. Similarly, the mean onset of Belg season was found to occur during the first dekad of April at Alaba Kulito and Angacha stations and second dekad of April at Fonko, Hosanna and Wulbereg stations. Based on the result obtained from MarkSim GCM of future scenarios, the average annual maximum temperature will be increased by about 0.8°C and 1.1°C for RCP 4.5 and RCP 8.5 scenarios in the 2030s and 1.2°C for RCP 4.5 and 1.8°C in RCP 8.5 scenarios in the 2050s. It is also predicted that the average annual minimum temperature will increase by about 0.2°C and 0.6°C in the 2030s for RCP 4.5 and RCP8.5 scenarios, respectively, and 0.7°C for RCP 4.5 and 1.5°C in RCP8.5 scenarios in the 2050s. However, projections of future rainfall suggest that mean annual rainfall would be likely to decrease by about 9.3% and 5.8% for RCP 4.5 and RCP8.5 scenarios in the 2030s and 8.7% for RCP 4.5 and 5.1% in RCP 8.5 scenarios in the 2050s. The CROPWAT model output shows that, the total amount of crop water requirement for maize would be expected to increase by 6.1 % and 8.8 % in 2030 and by 10.7% and 12.7% in 2050 for the RCP 4.5 and 8.5 scenarios, respectively. The overall result of this study shows that adaptation measures and water harvesting technologies are mandatory and recommended for the cropping season to have sustainable production to feed an increasing population.