Countries all over Africa have begun to exploit hydro-electric power, damming rivers and creating lakes hundreds of miles long, changing the way of life and environment in vast areas.
The benefits of these lakes are obvious - an unexpected source of fish, flood control, irrigation. But it's becoming ever more obvious that these assets are at least matched by the hazards the lakes create. Operation Noah, the project to save wildlife when Kariba was flooded, is well known; less well known is the fate of 50,000 Tongans made homeless at the same time, the spread of the dread disease Bilharzia into areas previously unaffected, the possibility of lakes changing the climate and even causing earthquakes.
It's easy to forget the pain of our own Industrial Revolution, but the pace of African development has been hastened by western investment. Tonight's Horizon asks if the price these countries are paying is not too great.