What Does a Dam Do?

Dam

  As a barrier across a river or stream, a dam stops the flow of water. It then stores the water, creating a lake or reservoir, and raises the level of the water almost as high as the dam itself. The stored water is available for many uses. The dam also raises the water surface from the level of the original riverbed to a higher level. This
permits water to be diverted by the natural flow of gravity to adjacent lands. The stored water also flows through hydraulic turbines, producing electric power that is used in homes and industries. Water released from the dam in uniform quantities assures water for fish and other wildlife in the stream below the dam. Otherwise, the stream would go dry there. Water released in larger quantities permits river navigation throughout the year. Where dams create large reservoirs, floodwaters can be held back and released gradually over longer periods of time without overflowing riverbanks.
  Reservoirs or lakes created by dams provide recreational areas for boating and swimming. They give refuge to fish and wildlife. They help preserve farm-lands by reducing soil erosion. Much soil erosion occurs when rivers flood their valleys, and swift floodwaters carry off the rich topsoils.