Trend Analysis of Climatic and Hydrological Parameters in Ajora-Woybo Watershed, Omo-Gibe River Basin, Ethiopia

Abstract

BackgroundIdentifying hydro-meteorological trends is basic for assessing change in climate and river discharge at watershed level. This study examined the long-term trends of rainfall, temperature, and discharge in the annual, monthly and seasonal time scale of Ajora-Woybo watershed in Ethiopia. The data span of rainfall and temperature is between 1990 and 2020 and that of discharge is between 1990 and 2015. Homogeneity test was performed by using Pettit and SNHT tests. Then Mann-Kendall and Sen's slope test for trend analysis and different variability measures were used. ResultsResults indicate that inhomogeneity was detected in annual rainfall data of Angacha and Areka stations. On annual basis, rainfall and discharge exhibited insignificant trends over time while showing a general decreasing pattern. On monthly basis, February and March were found to have significantly decreasing trend for rainfall. During the Kiremt season, rainfall increases and discharge decreases insignificantly. In contrast, maximum, minimum and mean annual temperatures exhibited significant trends with annual increment of 0.04oC, 0.01oC, and 0.025 oC per year respectively. Correlations of discharge with both temperature and rainfall have found to be weak in this study.ConclusionsThis trend, combined with population growth and increasing demand of water for agricultural activities exacerbates competing demands for water resources. Caution is therefore required when it comes to developing appropriate measures for the planning and sustainable development of the water resources in the watershed.