09/25/2026
What Is an Acre-Foot?
If you have ever heard someone talk about groundwater in terms of “acre-feet,” you may have wondered: What exactly is an acre-foot?
An acre-foot is a unit of measurement used to describe a volume of water. It is especially common when discussing groundwater, irrigation, reservoirs and water supplies.
So, How Much Water Is an Acre-Foot?
Imagine an acre of land—about the size of a football field without the end zones.
Now imagine covering that entire acre with one foot of water.
That amount of water is one acre-foot.
One acre-foot contains approximately 325,851 gallons of water.
That may be a difficult number to picture, but thinking about it as a three-dimensional volume makes it easier: one acre wide, one acre long and one foot deep.
Why Do We Use Acre-Feet?
Acre-feet are useful because water use can involve very large quantities. Instead of talking about hundreds of thousands or millions of gallons, water managers can use a unit that relates the volume of water to the land and water resources being managed.
For example, groundwater production and water supplies can be measured in acre-feet, making it easier to compare water use across different areas and purposes.
What does this have to do with the local Aquifers?
Here in the GGCD, groundwater from the Aquifers is an important water resource for communities, agriculture, businesses and industries.
Because so much groundwater is used across large areas, measuring water in acre-feet gives water managers a practical way to understand and manage the amount of water being produced.
A Simple Way to Remember It
1 acre-foot = 1 acre of land covered by 1 foot of water = approximately 325,851 gallons.
The next time you hear someone mention an “acre-foot” of water, you'll know they're talking about a lot of water—and a unit that helps us better understand and manage our groundwater resources.
