WITHDRAWN: Trend analysis of the extreme rainfall indices from Lake Tana Sub-Basin of the Upper Blue Nile, Ethiopia

Abstract

Ethiopia is among the African nations most susceptible to climate change because of its frequent droughts and heavy rainfall. Therefore, hydrological and water management problems require an investigation of regional variability and extreme rainfall patterns. This study analyzed the spatiotemporal trends of extreme rainfall in the Lake Tana Sub-Basin (LTSB) of Ethiopia's Upper Blue Nile Basin (UBNB) between 1981 and 2019. The trend and geographic patterns of ten extreme rainfall indices is evaluated using high-resolution data from Climate Hazards Group InfraRed Precipitation Stations (CHIRPS). We used RClimDex, an R software tool, to analyze the ten severe rainfall indices. The variability of the extreme rain indices was also assessed by applying the standard anomaly index (SAI). The trend analysis shows that the majority of rainfall indices decreased in the majority of station locations. Among the rainfall locations, the decreasing trend was only significant in 40% (CWD), 13.33% (R95p and R99p), and 6.66% (RX1day). In contrast, significant positive patterns were revealed in the incidence of rainfall events of R10mm, PRCPTOT, and CDD, with significant positive trends of 26.66% (R10mm) and 40% (PRCPTOT). Furthermore, a spatial distribution result of extreme rainfall trends reveals considerable variations between stations in spatial distribution. Thus, these findings point to the necessity of creating adaptation and mitigation plans for climate change variability within the sub-basin.