<P> The 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, irrigation water, and river flows . </P> <P> As the name suggests, an acre - foot is defined as the volume of one acre of surface area to a depth of one foot . </P> <P> Since an acre is defined as a chain by a furlong (i.e. 66 ft × 660 ft or 20.12 m × 201.17 m), an acre - foot is 43,560 cubic feet (1,233 m). </P> <P> There are two definitions of an acre - foot (differing by about 0.0006%), depending on whether the "foot" used is an "international foot" or a "U.S. survey foot". </P>

How many cubic meters in an acre foot