Hydroelectric energy simply means producing electrical energy from water energy. Water is a heavy substance and as we watch a white-water river or, better yet, observe the Niagara Falls we are left in no doubt as to the tremendous forces unleashed by cascading water.

Producing electricity is usually a matter of rotating a dynamo. Water passing over the blades of a turbine wheel is one method of doing this. In order to accomplish this a dam is usually constructed to block the flow of a river and to build up a reservoir of water for the turbines. The water is then piped from the bottom of the dam where its great steady pressure spins the turbines at a constant speed. The turbines are attached to a dynamo that then generates electrical energy.

Occasionally, a nation is lucky enough to have natural lakes high up in mountainous...