forebay (reservoir)

{{short description|Artificial pool of water ahead of a larger body of water}}

File:Vorsperre Schleusegrund.jpg forebay and pre-dam, part of the Schönbrunn Dam system]]

A forebay is an artificial pool of water in front of a larger body of water. The larger body of water may be natural or human-made.{{Cite web |last=McMahon |first=Mary |date=2023-05-08 |title=What is a Forebay? |url=http://www.allthescience.org/what-is-a-forebay.htm |access-date=13 June 2013 |website=All the Science |language=en-US}}

Forebays have a number of functions. 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. They may be used upstream of reservoirs to trap sediment and debris (sometimes called a sediment forebay[http://www.greenworks.tv/stormwater/sedimentforebay.htm Sediment Forebays] {{Webarchive|url=https://web.archive.org/web/20120623015556/http://www.greenworks.tv/stormwater/sedimentforebay.htm|date=2012-06-23}} at greenworks.tv. Retrieved 14 Jun 2013) in order to keep the reservoir clean. This entails the use of a dam built upstream of the main reservoir, called a forebay dam or pre-dam. Forebays may also be used upstream of lakes to prevent siltation. 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.

A forebay can also be a reservoir from which water is taken to run machinery such as turbines.{{Cite web |last= |first= |date= |title=Definition of Forebay |url=https://www.merriam-webster.com/dictionary/forebay |url-status=live |archive-url=https://web.archive.org/web/20210123024133/https://www.merriam-webster.com/dictionary/forebay |archive-date=Jan 23, 2021 |access-date=2020-06-24 |website=Merriam Webster |language=en}}