Once-through cooling water

Water (fresh or saline) that is withdrawn from a river, stream or other water body (manmade or natural), or a well, that is passed through a steam condenser one time, and then returned to the river or stream or other water body some distance from the intake. Once-through cooling water is used to exchange the heat from the steam condensers to the cooler water.

Source: Corrosion-Doctors.org