Analysis of rainfall and temperature variability for agricultural water management in the upper Genale river basin, Ethiopia

A better understanding of climate-induced changes and support for adaptation strategies requires knowledged of the spatiotemporal dynamics of climatic variables. This study aims to assess long-term changes in annual and seasonal rainfall and temperature for agricul-tural water management in the upper Genale river basin, Ethiopia. To achieve this objec-tive, long-term climate data from 13 stations between 1975 and 2018, as well as maxi-mum and minimum temperatures for six stations were collected from the Ethiopian Na-tional Meteorological Service Agency (NMA). The characteristics of rainfall (onset, cessa-tion, length of growing season, and crop water requirement) were assessed using the Coef-ficient of Variation (CV), Standard Rainfall Anomaly (SRA), and Precipitation Concentration Index (PCI). Additionally, the Mann-Kendall test and Sen's slope estimator were used to as-sess the trend and magnitude of changes in rainfall and temperature. The annual, winter, spring, summer and autumn CVs were 20%, 89%, 30%, 45%, and 32%, respectively. The stan-dardized anomalies of annual and seasonal rainfall for the climate stations indicated that the basin had a drier season than a wet season. The mean length of the growing season in Belg and Kiremt ranged from 43 to 79 days and 38 to 170 days, respectively. On an annual, summer, and autumn season basis, most rainfall stations showed a non-significant trend. In contrast, in the spring season, rainfall showed a decreasing but statistically insignifi-cant trend in all stations except Bensadaye, Bore, Telamokentise, and Yirba Muda stations. According to the analysis of the crop water requirements in the studied basin, supplemen-tal irrigation is essential to reducing yield reduction and crop failure during spring and autumn. In these seasons, maize and sorghum varieties required supplementary irrigation up to 202 mm and 252 mm, respectively. Annual and seasonal maximum and minimum temperatures showed an increasing trend at all the stations except Hagre Selam station. Generally, there was a spatially and temporally variable trend in rainfall while the temper-ature trend was increasing irrespective of the temporal and spatial factors. Thus, this study contributes to a better understanding of climate change in the basin and these findings can be used in planning for adaptation measures against a changing climate. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of African Institute of Mathematical Sciences / Next Einstein Initiative. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )