West Africa's Volta River Basin, home to 24 million people in six countries, will be badly hit by climate change, as dwindling water flows hit hydro-electric supplies and irrigation, scientists warned on Friday.

Water flows could fall by 24 percent by 2050 and by 45 percent by 2100 on the commonly-assumed basis that the region will warm by up to 3.6 degrees Celsius (6.5 degrees Fahrenheit) by century's end, they said.

The decline will have an impact on hydro-electric schemes, including the massive Akosombo Dam, which created Lake Volta, the world's largest man-made lake by surface area and the fourth biggest reservoir by volume.

By 2050, existing and planned hydro schemes will only perform at 52 percent of capacity, and by 2100 will run only at 28 percent because water flows will be so poor.

Irrigation would also be affected. By 2050, only 75 percent of annual irrigation water demand will be met. By 2100, this will fall to 32 percent.

The report is authored by specialists at the International Water Management Institute, Ghana's Council for Scientific and Industrial Research and the Potsdam Institute for Climate Impact Research in Germany.

It was released to coincide with a meeting of African agriculture scientists in Ghana.

The report called for the six countries sharing the basin -- Ghana, Burkina Faso, Benin, Cote d'Ivoire, Mali and Togo -- to broaden their mix of renewable energy, including wind and solar.

It also suggested ways of storing water to avoid evaporation. One method would be to replenish rural aquifers with water taken from rivers or reservoirs, a "recharging" technique that is increasingly used in other dry regions.

Forty-percent of the basin's economic output comes from agriculture, the report noted.

"An unreliable supply of water for irrigation will have serious consequences for a region where most people are farmers," said hydrologist Matthew McCartney, who headed the report.

"Beyond that, there is an urgent need to shift more food production away from rain-fed (irrigation) systems that are subject to the vagaries of climate."