An acre-foot is a unit of volume commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, and river flows.


It is defined by the volume of one acre of surface area to a depth of one foot.Since the area of one acre is defined as 66 by 660 feet (a chain by a furlong) then the volume of an acre-foot is exactly 43,560 cubic feet.Alternatively, this is approximately 325,851.4 U.S. gallons or 1,233.5 kL (or m³).


As a rule of thumb in U.S. water management, one acre-foot is taken to be the planned water usage of a suburban family household, annually. [ The state of Montana assumes 1.0 acre-foot per year for a family of five. See cite web
url =
title = Form No. 627 R8/03 Notice of Water Right
format = PDF
author = Water Rights Bureau, state of Montana
date = April 132004
accessdate = 2008-01-30
] In the desert South West, where water conservation is followed and often enforced, a typical family uses only about 0.25 acre-feet of water per year. [ Santa Fe, New Mexico rate averages 0.25 acre-feet per year per household. See cite web
url =
title = Water Use in Santa Fe: A survey of residential and commercial water use in the Santa Fe urban area
format = PDF
author = Planning Division, Planning & Land Use Department, City of Santa Fe, New Mexico
month = February | year = 2001
accessdate = 2008-01-30

The acre-foot (or more specifically the time rate unit of acre-foot per year) has been used historically in the U.S. in many water-management agreements, for example the Colorado River Compact, which divides 15 million acre-feet per year (586 m³/s) among seven western U.S. states.

ee also

* Cubic metres per second
* Cubic feet per second


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