The waters of Lake Victoria have risen to 13.43m, an all-time record.
The highest mark previously recorded was 13.41m, in May 1964.
The freshwater lake is shared by Uganda, Kenya and Tanzania, where the rising waters have caused destruction and displacement, leaving thousands of people homeless in recent weeks.
Sam Cheptoris, Uganda’s minister for water and environment, says the state electricity generation firm is now releasing 2,400 cubic meters of water per second at the River Nile in Jinja, to save the hydro-power dams from being washed away.
Uganda relies almost entirely on dams along the River Nile for its electricity needs.
Last month, the swelling waters led a floating island, estimated to have been about two acres, to break off the riverbank, blocking the intake gates of one of the dams and causing a brief nationwide power cut.
The Nile flows into Lake Kyoga, north of the capital Kampala, where the water being spilt downstream has also caused the lake to swell, displacing families and damaging farms.
East Africa is currently experiencing heavier than usual rains, which are predicted to continue throughout May.