Eric Wolanski of Australia's James Cook University and Yustina Kiwango of Tanzania National Parks said the dams' overuse of water decreased the lake level by at least 6.5 feet from 2000-06.
The dams, located at the outlet of Lake Victoria in Uganda, have been using water at a rate up to 50 percent above the allowable discharge agreed by Uganda and Egypt in 1957, the scientists said. That has dried papyrus wetlands fringing the lake, resulting in an 80 percent collapse in tilapia that use the wetlands as a refuge.
The researchers said the loss of the fish -- a key staple of the local population -- threatens the food security of people depending on the lake in Uganda, Kenya and Tanzania.
"The future of Lake Victoria and its people is very closely related to the future of its papyrus wetlands," the researchers said. They urged officials in Kenya, Uganda and Tanzania to address the issue.
The study appears online in the journal Wetlands Ecology and Management.