Legal Definitions - acre-foot

An acre-foot is a specialized unit of measurement used to quantify large volumes of water. It represents the amount of water required to cover one acre of land to a depth of one foot. This measurement is particularly useful in fields such as water resource management, irrigation, and civil engineering, where substantial quantities of water need to be precisely measured and allocated. To put it into perspective, one acre-foot is equivalent to approximately 325,850 gallons of water.

• Example 1: Reservoir Capacity

  Imagine a large reservoir that supplies drinking water to several cities. Engineers might describe its total storage capacity as 250,000 acre-feet. This statement means the reservoir is capable of holding a volume of water sufficient to cover 250,000 acres of land to a depth of one foot, indicating its immense capacity to store water for municipal use and drought resilience.

• Example 2: Agricultural Water Rights

  In a region where water is scarce, a state water agency might allocate water rights to farmers based on their land size and crop type. A farmer with a large orchard might be granted an annual water right of 75 acre-feet. This allocation signifies that the farmer is legally permitted to draw a volume of water equivalent to covering 75 acres of land with one foot of water over the year to irrigate their crops, ensuring sustainable water use within the agricultural community.

• Example 3: River Basin Management

  A river basin authority might track the annual runoff from snowmelt into a major river system. They could report that the basin received 1.2 million acre-feet of water from spring snowmelt. This measurement indicates the total volume of water that flowed into the river system from the melting snow, providing crucial data for managing downstream water supplies, flood control, and environmental flows.