Draft PPS18: Renewable Energy
E13. After use, the water is returned to the natural watercourse via a concrete or masonry channel connecting the turbine house to the watercourse. To avoid flooding the turbine, this channel should have a gradient sufficient to allow free discharge of water. A screen to prevent the ingress of fish is often incorporated, and occasionally the tailrace is an underground structure.
Annex 1 Small Hydro Technology: The Tailrace