IMPACT OF CLIMATE CHANGE ON CROP AND IRRIGATION WATER REQUIREMENT: THE CASE OF LAKE ZIWAY CATCHMENT, ETHIOPIA

Abstract

A good understanding of water resources and climate change variability can help to manage them sustainably and to develop mitigation measures. This study was conducted to analyze the impact of climate change on crop and irrigation water requirements in the Lake Ziway catchment, Ethiopia. The impact of climate change was evaluated using projected Marksim general circulation model (GCM) data, and crop water and irrigation water requirements for maize during the baseline and future periods were determined using CROPWAT 8.0. The annual rainfall increased by 0.23% in representative concentration pathways (RCP 4.5) and 1.2% in RCP 8.5 during 2030, 2.4% in RCP 4.5 and 5.9% in RCP 8.5 during 2060, and by 3.5% in RCP 4.5 and 14.9% in RCP 8.5 during 2090. The projected annual minimum temperature was increasing by 12 ⁰C and 12.2⁰C in 2030; for 2060, it was 12.9⁰C and 13.8 ⁰C, and the increment was projected to be high in 2090, which is 13.3⁰C and 15.6⁰C for both RCP4.5 and RCP8.5 scenarios. The projected annual maximum temperature in 2030 increased by 25.6 °C and 25.7 °C; the increase was 26.3 °C and 27.1 °C in the 2060s and 26.6 °C and 28.7 °C in the 2090s, in both RCP 4.5 and RCP 8.5, respectively. The change in reference evapotranspiration (ETO) calculated from the base period was -1.08, 0.54, and 1.06% during 2030, 2060, and 2090, respectively, for RCP4.5 and 0.54, 2.4, and 6.25% during 2030, 2060, and 2090, respectively, for RCP8.5. The crop water requirement (CWR) was determined to increase by -1.24, 0.18, and 0.91% for RCP4.5 and by -0.99, 1.70, and 5.03 % for RCP8.5 scenarios in the 2030s, 2060s, and 2090s from the base period for the same level of production. The irrigation water required was determined to increase by 24%, 19.8%, and 21.6%, respectively, in the 2030s, 2060s, and 2090s for RCP4.5 and increase by 14.4% and 12.38%, respectively, in the 2030s and 2060s and decrease by -19.5% in the future period of the 2090s for RCP8.5 scenarios. Generally, the results of this study indicate that the rainfall and temperature projected significant change compared to the baseline period, and there was an increase in maize water needs that shows the catchment was sensitive to climate change