Some lakes are shrinking due to deforestation, climate change or poor farming methods, evidence of the need for better cross-border cooperation to ensure access to life's most precious resource, the UN Environment Programme (UNEP) said in the report published Monday.
The report, based on a comparison of contemporary satellite imagery of Africa's lakes and satellite photographs taken over recent decades, was released at the opening of an international conference on lakes in Kenya's capital, Nairobi.
Experts say that on a continent where most people have no access to safe drinking water, the study should serve as a strong warning about the need for better environmental policies.
"Africa's freshwater supply, including lakes, is threatened by depletion of water resources through pollution, environmental degradation and deforestation," said the report, called Africa's Lakes: An Atlas of Environmental Change.
"High population in Africa is the major cause of degradation and pollution of most African Lakes, as every one exploits aquatic resources to make a living," the report said.
According to the report, 90% of
Africa's water is used in farming
According to the UN, two-thirds of the rural population and a quarter of the urban population in Africa are without safe drinking water, while more lack proper sanitation.
"The sustainable management of Africa's lakes must be part of the equation. Otherwise we face increasing tensions and instability as rising populations compete for life's most precious of precious resources," UNEP chief Klaus Toepfer said.
Up to 90% of Africa's water is used in farming, of which 40% to 60% is lost to seepage and evaporation, says the UNEP Atlas.
Lake Victoria - Africa's largest freshwater lake, which provides fishing and transport for 30 million people - has dropped by one metre in the past decade, the report said.
The report also details the rapid shrinking of Lake Songor
in Ghana, partly because of salt production, "extraordinary" changes in the Zambezi river system after the building of the Cahora Bassa dam site, and the near 90% shrinkage of Lake Chad.
UNEP said the damming of rivers combined with the disposal of untreated sewage and industrial pollution had reduced Africa's fish catch, particularly in the Nile Delta and Lake Chad.
"Africa's freshwater supply, including lakes, is threatened by depletion of water resources through pollution, environmental degradation and deforestation"
An accompanying report on the quality of legal pacts governing access to lakes in Africa highlights several possible flashpoints of political instability, UNEP said.
The report, Hydropolitical Vulnerability and Resilience along International Waters in Africa, points to the Volta river basin in West Africa, shared among Benin, Burkina Faso, Ivory Coast, Ghana, Mali and Togo, as being a concern.
The study, by UNEP and the University of Oregon, says over the next two decades population levels are set to double in the basin to 40 million, causing a dramatic rise in demand for
Meanwhile, rainfall and river flows in the region have declined steadily in the past 30 years.