The British Dam Society
Caring for dams, people and the environment

About Dams

Back to spillwaysSpillways & Outlets - Compensation water

When a dam is constructed across a river valley, an outlet pipe, usually in a tunnel, must be provided from the reservoir to allow some water to continue to flow in the river downstream. Sufficient water must be let through to maintain the fish and wildlife that use the river, and the natural vegetation in and around it. This water is called compensation water.