Climate change posed agricultural drought and potential of rainy season for effective agricultural water management, Kesem sub-basin, Awash Basin, Ethiopia

The Intergovernmental Panel on Climate Change concluded that climate has changed over the past century and the trend is anticipated to continue in the future. This study examines climate change posed drought and potential of rainy season rainfall in Kesem sub-basin. Rainfall variability is examined using statistical descriptors. Also, the onset and cessation dates, length of growing season, and probability of dry and wet spell are analyzed using INSTAT Plus software. On the other hand, long-term drought is analyzed using reconnaissance drought index. Rainfall variability result showed high coefficient of variance (CV) of 46.8 to 179.2% on monthly and 39.1% on annual basis. The mean duration of the main rainy season is 91 days with standard deviation of 18.5 days and CV of 20.4%. The probability of dry decade in the main rainy season is more than 50% for the 16th to 18th and 25th to 27th decades. Whereas probability occurrences of dry decades preceded by dry decades were more than 50% for decades 16th to 18th and 23th to 27th. Potential evapotranspiration showed increment of 25.9 mm from the base period for RCP 4.5 (2020) and 26.7 mm for RCP 8.5 (2020), and 55 mm for RCP4.5 (2050) and 56.8 mm for RCP8.5 (2050). Regarding the long-term drought, there were 9.7% extreme, 6.5% severe, 3.2% moderate, and 48.4% mild drought on the basis of observed data. The inter-annual variability of growing seasons, probability occurrence of dry decade, and drought during growing season are revealed. So, policymakers need to consider supplementary irrigation for crops in the area because there are high probability occurrences of dry decades.