RESERVOIR n.
A place where anything is kept in store; especially, a place where water is collected and kept for use when wanted, as to supply a fountain, a canal, or a city by means of aqueducts, or to drive a mill wheel, or the like.
WASH n.
Substances collected and deposited by the action of water; as, the wash of a sewer, of a river, etc. The wash of pastures, fields, commons, and roads, where rain water hath a long time settled. Mortimer.