Open loop heat pumps return the water to its source, or more accurately, very close to its source. Using a stream as the source the return would be several feet down stream of the inlet, for a pond they would be tens of feet apart, or for your well the intake should be a few feet off the bottom with the return several feet above that. The water is a vehicle for moving heat, it doesn't get consumed. Are you talking about evaporative loss from a cooling tower? Tom