Lake Muhazi is a long thin shallow lake in the east of Rwanda. The bulk of the lake lies in the Eastern Province, with the western end forming the border between the Northern and Kigali Provinces. It is a flooded valley lake, lying predominantly in an east to west direction, but with numerous offshoots in a north to south direction, formerly the location of tributaries. The lake has a concrete dam at the western end, constructed in 1999 to replace an earth dam which had existed since time immemorial. The lake empties into the Nyabugogo River, which flows southwards to Kigali where it meets the Nyabarongo River, part of the upper Nile.