Tailrace

Part of speech: noun

Definitions

1. The channel or passage that carries water away from a waterwheel, turbine, or other hydraulic machinery after it has been used to generate power
2. A water conduit that directs flow downstream from a waterwheel or turbine following energy extraction
3. The outlet channel through which water exits from a waterwheel or turbine and returns to the natural watercourse

Etymology: Tailrace is a compound of "tail" and "race," and the two parts carry their literal senses. A race in this sense is an artificial channel or watercourse, the sort that carries water away from a mill wheel or turbine. The tailrace is the channel at the back end of such a machine, the stretch where water flows out after it has done its work, so the name simply describes its position relative to the wheel. The word is therefore a plain descriptive coinage rather than a story of shifted meaning. "Race" here comes from the older sense of a current or a channel of running water, and its appearance in technical vocabulary is what makes the compound transparent: the water's journey is named in the order it happens, beginning with the headrace that feeds the wheel and ending with the tailrace that releases it.

Synonyms: tailwater, discharge channel