How much exactly is an acre foot of water?

December 2, 2016

Communications & Public Affairs Office

The Gila River Indian Community has rights to a large amount of water, an annual entitlement of 653,500 acre feet to be exact, and when large amounts of water are discussed the term “acre foot” is commonly used.

For most people it is difficult to conceptualize what an acre foot is and how large the Community’s water rights are.  

So to help put this term in perspective consider the following tidbits.

An acre foot contains 325,851 gallons. According to the Environmental Protection Agency the average family of four uses about 400 gallons of water per day, or 146,000 gallons per year.

So an acre foot is more than enough water to supply two households for one year. According to the National Association of Home Builders the typical American subdivision has a little more than two homes on each acre of land. The median size of an American subdivision is 24 acres. So the average American 24 acre subdivision uses about 24 acre feet of water per year.

Residential use of water is fairly small compared to farming. Typical flood irrigation uses about five to six acre feet of water to farm an acre of land for a year. Currently, about 36,000 acres of land are being farmed within the Community which requires 180,000 to 216,000 acre-feet of water each year. In comparison, Phoenix and its 1.5 million residents need about 180,000 acre-feet of water each year for domestic purposes.

Last year the Community used a little over 222,000 acre feet of water on its lands. Most of this water was used for farming. Of this amount approximately 87,000 acre feet came from the Gila River and other surface water sources, 86,000 acre feet came from wells, 32,000 was Central Arizona Project water, and 17,000 acre feet was reclaimed water.

Currently, the Community only uses about a third of its water entitlement for use on the reservation, but it has plans to use more water as farming expands. Fortunately, the Community has plenty of long term water supply. To put the Community’s long term water supply amounts in perspective, over a 100 year period the Community’s water entitlement exceeds 65 million acre feet – which is over 22 trillion gallons of water. By any measure this is a lot.    

If you have water related questions that you would like answered, please contact the CPAO at cpao@gric.nsn.us.