the volume contained by an acre, one foot deep.

The A measure of water storage capacity in a hydrosystem reservoir or a specific volume of water. One acre-foot is the volume of water needed to cover one acre to a depth of one foot. The average Ontario household of four uses about one acre-foot of water per year.

Unit of volume; one acre of producing formation one foot thick. One acre foot equals 7,758 barrels, 325,829 gallons or 43,560 cubic feet.