Ethiopia not Sudan, it will massively increase Ethiopia’s energy generation capacity in addition to providing flood control in the Blue Nile Valley. The stated main purpose of the dam is energy generation but of course it will have capacity for providing irrigation water as well.

It has caused strained relations with Sudan and Egypt due to impounding the water before it enters those two countries, though it has been stated that it may actually increase available water downstream (due to higher evaporation rates in the downstream sectors of the Nile). Sudan and Egypt have even suggested military action in response to its construction.