Evaluation of Extreme Rainfall and Temperature Variability (In Upper Blue Nile, Ethiopia)

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Addis Ababa University


Climate is perceived to be changing worldwide and there has been growing concern as to the direction and effects of these changes. The upper Blue Nile river basin is one of the potential river basins in the country where many development projects are undergoing currently with out having detail climate change situational analysis. As a trans-boundary river basin, this area attracts the attention of some neighboring countries. For sound water resources planning and safeguarding of structures it is important to detect the possible climate change and variability of decisive metrological events like temperature, and precipitation. Therefore the concern of this research is to evaluate the variability of extreme events with regard to climate change for the upper Blue Nile river basin using climate indices. A suite of climate change indices derived from daily temperature and precipitation data, with a primary focus on extreme events, were computed and analyzed with specially designed computer Software. ClimeDex Version 1.3 Software is designed to analyze daily metrological data input and generates climate indices which intern indicates how temperatures and precipitation are varying in the upper Blue Nile River basin. The whole trend analysis result of the basin showed no change over days having a rainfall amount 10mm/day or above. Only 3 days per decade join the upper rainfall extremes in the basin. Unlike precipitation, there is consistent increase in both minimum and maximum temperatures extremes. The result showed that 46 days per decade joins the upper extremes of maximum temperature and 43 days per decade leave the bottom extremes and join the next intermediate category. There is an increase of 38 days per decade in the upper extremes and surprisingly 68 days per decade leave the bottom extremes of minimum temperature and appear above the 5th percentile of the base period. Further research can improve the accuracy of the results. Generally the over all trend analysis result showed there are slight and non-consistence variability in precipitation extremes and significant variability in temperature extremes.



Blue Nile; Ethiopia