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Climate change impacts on hydrology and water resources of the Upper Blue Nile River Basin, Ethiopia
This report aims to evaluate the impacts of climate change on both hydrologic regimes and water resources of the Upper Blue Nile River Basin in Ethiopia where observed hydrologic data are limited. The downstream countries of the Nile River Basin are sensitive to the variability of runoff from the Ethiopian part of the basin. This report presents three steps for analyzing climate change impacts on hydrology and water resources. The first is the construction of the climate change scenarios whereby the outcomes of multiple general circulation models (GCMs) are used to perturb the baseline climate scenario representing the current precipitation and temperature patterns. The second is runoff simulation by using a simple two-tank hydrologic model due to the limited data availability and the scale of the sub-basins. The hydrologic model uses the constructed climate scenarios as input to predict runoff. The model parameters for ungauged parts of the basin are estimated by means of hydrologic regionalization. In the final step, climate change impacts on hydrology and water resources are examined using a set of indices. The impacts of potential future hydropower dam operations in the upstream parts of the Nile Basin under future climate scenarios on downstream countries are also assessed. The results suggest that (1) the climate in most of the Upper Blue Nile River Basin is likely to become wetter and warmer in the 2050s (2040-2069); (2) low flows may become higher and severe mid- to long-term droughts are likely to become less frequent throughout the entire basin; and (3) the potential future dam operations are unlikely to significantly affect the water availability to Sudan and Egypt based on predicted outflows from six GCMs and many dam operation scenarios. The results, however uncertain with existing accuracy of climate models, suggest that the region is likely to have the future potential to produce hydropower, increase flow duration, and increase water storage capacity without affecting outflows to the riparian countries in the 2050s.