International Rivers Network, an environmental advocacy group in California, just published the May 2013 International Panel of Experts 48-page report on the Grand Ethiopian Renaissance Dam Project. There were two experts each from Ethiopia, Egypt, and Sudan and four international experts on the panel. While the highly technical report contains no shocking surprises, it does raise a number of concerns.
The findings and recommendations begin on page 20. The concerns center around the spillway for the main dam, several issues dealing with the saddle dam, evaporation in the reservoir behind the dam, and the impact of climate change. Page 41 contains the key adverse and positive impacts for Egypt. There are a number of recommendations for more study.
You can find further comment on the document on the blog of Jennifer Veilleux, an Oregon State University PhD student who is studying the Renaissance Dam.
On 3 April 2014, International Rivers Network commented on the report by the experts. On 11 April 2014, the Ethiopian Ministry of Foreign Affairs then issued a rebuttal to the analysis offered by International Rivers.