What formula is used to calculate water volume in acre-feet?

The correct formula to calculate water volume in acre-feet is based on the concept that an acre-foot represents the volume of water required to cover one acre of land to a depth of one foot. The formula states that acre-feet equals the surface area multiplied by the average depth of water.

To understand this further, consider that the surface area of the body of water (measured in acres) gives the extent of the water surface. When you multiply this by the average depth (measured in feet), you effectively calculate the total volume of water present in that area, expressed in acre-feet. For example, if you have a pond that has a surface area of 2 acres and an average depth of 3 feet, the volume would be calculated as 2 acres multiplied by 3 feet, resulting in 6 acre-feet of water.

The other options do not accurately represent the relationship between surface area and depth necessary to derive the volume in acre-feet, thus making them unsuitable for this calculation.