Forebay (reservoir)

The larger body of water may be natural or human-made.

They are used in flood control to act as a buffer during flooding or storm surges, impounding water and releasing in a controlled way into the larger waterbody.

Some forebays are used simply to create a natural habitat for flora and fauna, to counterbalance the environmental impact of a dam or reservoir.

Forebays vary greatly in size depending on their situation and purpose.

[1] A forebay can also be a reservoir from which water is taken to run machinery such as turbines.