Sep 08 2014Share

Mystery Of Lost Water Wastes Precious Resource And Money

By Kathleen Ferris

Solving the mystery of Lost and Unaccounted for Water can save a city money and conserve water on a grand scale.

Lost and Unaccounted for Water, also known as non-revenue water, is the difference between the volume of drinking water treated by a city minus the volume of drinking water the city delivers to its customers. In a perfect world the amounts would match. They rarely do.

Lost water is more than a conservation concern. No one is paying for the missing gallons of expensive, highly treated drinking water. That means water departments and companies are losing money.

So, how does this highly treated drinking water get lost?

EPA and Arizona officials say much of it is lost through infrastructure that allows water to overflow or leak while the water is being treated and delivered. Some water loss is blamed on theft. Some water actually reaches its destination, but never gets counted because meters are old or faulty or billing calculations are wrong.

EPA estimates that 16 percent of U.S. drinking water is lost and 75 percent of that lost water could be recovered.

Since the Arizona Groundwater Management Act of 1980, the state has required its largest cities and towns, as well as its largest private water companies, to keep the rate of Lost and Unaccounted for Water to 10 percent or less. Since 1992, the regulation limits lost water to 10 percent on either an annual basis or three-year average basis. This requirement is one of the toughest of its kind in the United States.

The Arizona Department of Water Resources reports that only about 7 or 8 of the 86 large suppliers struggle to stay within the 10 percent loss requirement. Those cities and companies not in compliance can be fined up to a maximum of $10,000 each day they are in violation, depending on circumstances such as the severity and duration of losses. The state, however, prefers to impose corrective measures on violators, such as requiring them to develop and improve conservation and efficiency within their systems.

From 2009 through 2013, AMWUA’s 10 member cities had a cumulative water loss rate of 6.91 percent, nearly 60 percent below the national average. In 2013, three AMWUA cities, Tempe, Peoria, and Mesa, had a 3-year average loss of less than 4 percent.

When considering the drama of water loss, the size of a city is important.

For example, in Phoenix a loss of 1 percent means 3,029 acre-feet of missing water. In Goodyear a 1 percent loss means 108 acre-feet of missing water. (One acre-foot covers an acre of ground to a depth of one foot and provides enough water to serve about 2.5 Phoenix-area households for a year.)

Lost and Unaccounted for Water is becoming a bigger issue as cities around the world look for ways to save during times of drought and climate change. Here is an interesting New York Times opinion piece about water loss and recovery. There is more information at the U.S. EPA.

For 45 years, Arizona Municipal Water Users Association has worked to protect our member cities’ ability to provide assured, safe and sustainable water supplies to their communities. For more water information visit

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