Trend Analysis of Hydrometeorological Data of Gilgel Gibe Catchment, Ethiopia

Abstract

Trend analysis of hydrometeorological data is vital for proper water resources planning and management. is paper examines the trends of the hydrometeorological data in Gilgel Gibe catchment and whether the trends are signi cant. Daily rainfall, tem perature, and stream ow data of the stations in/around (nearby) the catchment (7 stations for rainfall, 4 stations for temperatures, and 6 stations for stream ow) for a period longer than 25 years were collected and then analyzed to detect the variability and the changes in trend. Prior to conducting trend tests, the missed data were lled, and their inconsistencies were also adjusted. e nonparametric Mann-Kendall test along with Sen’s slope technique was employed to detect monotonic trends in the data series. e results showed that, on average, the rainfall exhibits an insigni cant increasing tendency. It was also observed that there is, in general, an increasing trend in temperature (both maximum and minimum) in the study area. e analysis of the stream ows indicated that only one station (Bulbul Nr. Serbo) showed a positive slope at a 5% signi cance level. Two stations (Aweitu Nr. Babu and Gibe Nr. Seka) showed a slightly increasing trend, whereas the remaining 3 stations (Gibe Nr. Assendabo, Aweitu at Jimma, and Kitto Nr. Jimma) indicated an insigni cant decreasing trend. e stream ow of the catchment generally shows a tiny decreasing tendency (0.007% per year) at its outlet. However, the results in general speci ed statistically insigni cant trend changes of the hydrometrological data of the study catchment.