Tailraces

Tailraces are channels that carry water away from hydroelectric turbines after use, discharging downstream into a river or tailwater system. They form the final segment of a dam’s hydraulic system and can be open channels, culverts, or tunnels depending on site conditions.

Water exits the turbine into the tailrace and flows to the downstream reach. Tailrace geometry—width, depth, and slope—must accommodate turbine discharge and control velocity to prevent scour. Energy-dissipation structures such as stilling basins or plunge pools reduce jet energy before outlet.

Tailraces affect downstream hydraulics and ecology by transporting used water while preserving environmental flows and mixing with the river. Discharge conditions influence sediment transport, bedform, and local habitat. Where fish passage is a concern, screens or bypasses may be included near the outlet.

Configurations vary by plant type. Conventional dams may use long open channels; run-of-river sites may employ shorter channels; pumped-storage facilities often have enclosed tails. Mountain sites may favor tunnels, while flatter sites use open channels for maintenance access and flexibility.

Maintenance and safety are important for tailraces. Regular inspection of gates, liners, erosion protections, and dissipation devices helps prevent damage and downstream hazards. The tailrace is a key element in dam performance and river dynamics.