Mill pond

A mill pond (or millpond) is a body of water used as a reservoir for a water-powered mill.

Description
Mill ponds were often created through the construction of a mill dam or weir (and mill stream) across a waterway. In many places, the common proper name Mill Pond has remained even though the mill has long since gone. It may be fed by a man-made stream, known by several terms including leat and mill stream. The channel or stream leading from the mill pond is the mill race, which together with weirs, dams, channels and the terrain establishing the mill pond, delivers water to the mill wheel to convert potential and/or kinetic energy of the water to mechanical energy by rotating the mill wheel. The production of mechanical power is the purpose of this civil engineering hydraulic system.

The term mill pond is often used colloquially and in literature to refer to a very flat body of water. Witnesses of the loss of RMS Titanic reported that the sea was "like a mill pond".