Recent Approaches to Climate Change Impacts on Hydrological Extremes in the Upper Blue Nile Basin, Ethiopia

Extreme hydrological variables are influenced by spatial and temporal climatic change, which is mainly caused by meteorological anomalies, catchment topographical processes, and human activities. The hydrological cycle process was mainly affected by climate change dynamics. The major goal of this review paper is to show how recent approaches to global climate change have affected hydrological extremes in the Upper Blue Nile Basin. This paper presented a systematic review, which defines and conceptualizes research findings of hydrological extremes of past decades and also future climate circumstances. In regards to precipitation, temperature, as well as streamflow extreme trends and variability, were reviewed within the basin using academic visibility engines (e.g., Science Direct, Google Scholars, and Scopus Database). The result demonstrated that extreme flood events were more likely to occur during the La Niña years, with a 67% probability of extreme flooding, and drought was more likely to occur during the El Niño years, with an 83% probability of drought. The literature shows that the trends of annual rainfall have not changed within the Upper Blue Nile Basin both in history and in future projections. However, seasonal and monthly rainfalls have both increasing and decreasing trends. Rainfall showed an increasing trend at the majority of the stations in May, June, July, August, and September, as well as in the summer season (June–September). In future climate conditions, both mean temperature and streamflow indicate an upward trend. The upper Blue Nile Basin is notable for its erratic and seasonal rainfall, as well as its sloppy and fragile terrain. To avoid uncertainty and bias in the basin, this characteristic could be incorporated while performing climate and hydrological modeling and climate downscaling techniques. The results appear to show signals of climate change and variability in the Upper Blue Nile Basin which should be taken into account for future water resources allocation and management.