acre-foot

An acre foot volume. Note that drawing is not to scale.

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.

Definition

It is defined by the volume of water necessary to cover 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 325,851.42 U.S. gallons, or 1,233.5 cubic meters. 1,233,500 litre

Discussion

As a rule of thumb in U.S. water management, one acre foot is taken to be roughly the amount of water used annually by between 1 and 3 suburban family households of four, per year. 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.

See also

• Cubic metres per second
• Cubic feet per second

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