An acre-foot is a unit of volume used to measure large quantities of water, particularly in agriculture and reservoir management. It represents the volume of water needed to cover one acre of land to a depth of one foot. This is equivalent to 43,560 cubic feet or approximately 325,851 gallons. Calculating this volume involves multiplying the surface area (in acres) by the depth (in feet). For example, a reservoir with a surface area of 100 acres and an average depth of 20 feet contains 2,000 acre-feet of water.
This unit provides a practical way to visualize and manage substantial water resources. It simplifies communication among stakeholders, from farmers and water managers to policymakers, by providing a readily understandable metric. Historically, the acre-foot emerged as a convenient measure in regions where land area and irrigation needs were paramount. Its continued use highlights its enduring relevance in water resource planning and allocation, particularly in arid and semi-arid environments.
