Climate Change in Africa: Shrinking lakes and the role of dams

More on the localised effects of dams. This article also tells the story of how the lives of millions may be affected if climate change predictions are correct. This post provides us with some clues as to how the fragile economies in Africa are likely to come under ever increasing pressures in the next 20 years or so.

Vast African Lake Levels Dropping Fast

At 27,000 square miles, the size of Ireland, Victoria is the greatest of Africa's Great Lakes _ the biggest freshwater body after Lake Superior. And it has dropped fast, at least six feet in the past three years, and by as much as a half-inch a day this year before November rains stabilized things.

The outflow through two hydroelectric dams at Jinja is part of the problem _ a tiny part, says the Uganda government, or half the problem, say environmentalists. But much of what is happening to Victoria and other lakes across the heart of Africa is attributable to years of drought and rising temperatures, conditions that starve the lakes of inflowing water and evaporate more of the water they have.

An extreme example lies 1,500 miles northwest of here, deeper in the drought zone, where Lake Chad, once the world's sixth-largest, has shrunk to 2 percent of its 1960s size. And the African map abounds with other, less startling examples, from Lake Turkana in northern Kenya, getting half the inflow it once did, to the great Lake Tanganyika south of here, whose level dropped over five feet in five years.

"All these lakes are extremely sensitive to climate change," the U.N. Environment Program warned in a global water assessment two years ago.

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A further dramatic drop in Victoria's water levels might even turn off this spigot for the Nile, a lifeline for more than 100 million Egyptians, Sudanese and others.

Now that is an externality - the use of dams for electricity in Uganda and Tanzania being resposible for the livilhoods of millions many miles away.

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Lake Chad's near-disappearance, for example, stems in part from overuse of its source waters for irrigation. Deforestation around Lake Victoria, shared by Uganda, Kenya and Tanzania, makes the area a less efficient rain "catchment" for the lake, and overfishing and pollution are damaging its $400-million-a-year fishing industry. Kenya's Rift Valley lakes, some just a few feet deep, have always fluctuated in size, even drying up with drought.

But African leaders say things are different this time, because long-term climate change may eclipse other factors.

"These cycles, when they've happened, they haven't happened under the circumstances pertaining now _ the global warming, overpopulation, degradation," said Maria Mutagamba, Uganda's water and environment minister.

Now for the economic impact of Dams and how countries have become reliant on hydo-electric as a means of power.

For 30 million people living in its basin, Lake Victoria is a vital source _ of livelihoods and food, of water, of transportation, of electric power.

Almost 200 miles across the lake from here, Tanzanian authorities have reduced water supplies to the city of Mwanza because an intake pipe was left high and dry. The same is happening in Uganda, where German engineer Erhard Schulte is pushing work crews to finish refitting Entebbe's city water plant, extending its intake pipe 1,000 feet farther out into the lake.

"The old Britisher who designed the original plant never expected the lake would drop this way," Schulte told a visitor.

Perhaps the worst impact is on power supplies. Tanzanian factories have shut down because the rivers powering hydroelectric dams, and replenishing Lake Victoria, are running dry. Kampala, a city of more than 1 million, has endured hours-long blackouts daily.

Uganda's two big hydro dams, side by side on the Victoria Nile, the lake's only outlet, are victims and _ some say _ prime suspects in the crisis.

In 2003, facing growing Ugandan demand for electricity, the Nalubaale and Kiira dams produced a peak 265 megawatts of power. In the process, their operators began overshooting long-standing formulas regulating flow of water out of the lake, an independent hydrologist later concluded.

That outside study, cited by environmentalists, contends 55 percent of the lake-level drop since 2003 is traceable to excessive outflow. But the dams' private operators and Ugandan officials strongly dispute that.

Paul Mubiru, Ugandan energy commissioner, says the dams have had a "negligible" impact on Lake Victoria, and points to Lake Tanganyika's similar fall in levels _ with no dams involved.

Earlier this year, the operators announced they were reducing the dam outflows, "but our observations show that even with the reduced outflow, the water loss is still on the increase," Mutagamba, the water minister, told the AP.

Falling lake levels, meantime, mean lower "head" pressure at the dams. Their output has dropped to 120 megawatts, pushing Uganda deeper into economic crisis.

The economic feedback mechanisms of climate change are complex but the result may be more economic and political conflict than are currently expected.