An acre-foot of water, in layman’s terms

In the Western water world, measuring in gallons or cubic feet isn’t quite enough.

Unless Nevadans are attuned to the inner workings of their state’s water issues, they may not have grasped the concept of an acre-foot — a measurement commonly used to gauge water volume and use.

It’s as self-explanatory as it sounds: An acre-foot of water is enough to cover an acre of land that is 1 foot deep, according to the Water Education Foundation. One acre is roughly the size of a standard football field.

That’s a lot of water. An acre-foot translates to 325,851 gallons or 43,560 cubic feet — enough to sustain about two single-family households for a year.

Understanding how much an acre-foot really is comes in handy when reading about water negotiations across the Colorado River Basin or the storage levels of Lake Mead. Water rights, or the legal property rights to use water in the West, are also measured in acre-feet.

Still, the question remains: Why can’t we just use gallons? The answer is that the enormous amount of water is best communicated in a smaller number.

For instance, water managers often reference the Colorado River’s “structural deficit,” or the amount of water lost to evaporation and transportation. Coming in at 1.5 million acre-feet a year, that vast quantity of water is better understood in acre-feet, rather than more than 488 billion gallons.

To calculate how many gallons are in an acre-foot, online converters can be helpful.