May 18 2015Share

Study: Western Cities Know How To Save And Reuse Water

By Kathleen Ferris

Along with thirty conservation leaders and experts in the southwest, I've been wrestling with a project since 2013. It's part of the Moving Forward effort initiated by the Bureau of Reclamation and the seven Colorado Basin states that followed completion of the Colorado River Basin Water Supply and Demand Study of 2012.

The study confirmed that action is needed to prevent significant shortfalls of Colorado River water to meet demands in coming decades. The study also found that a wide range of solutions is needed, including municipal and industrial water conservation and reuse.

I co-chair a workgroup established in response to this study that has been investigating water use in ten large metropolitan areas that receive Colorado River water. These metropolitan areas include central Arizona, southern California, southern Nevada, and the Front Range in Colorado.

Our specific assignment: document conservation and water reuse efforts in these metropolitan areas over the last 25 years, highlight successful programs, and identify opportunities to build on these successes.

The workgroup’s conclusions can be summed up in simple math. If customers in these ten metro areas had continued to consume water as they did in 1990, demand for water would have been 1.7 million acre-feet higher in 2010 than it was. That’s a lot of water not consumed. One acre-foot is enough to serve 2.5 Phoenix households for a year. 

There's more. The workgroup found that all ten of the metro areas treat wastewater and reuse it for beneficial purposes. Together the ten areas reused a total of 709,000 acre-feet of water in 2012. Clearly, these metropolitan areas are making considerable progress in water conservation and reuse.

The workgroup also came up against a hard economic fact. Conservation and reuse may not result in substantial reductions in Colorado River water use in the future. The water cities save will be used to offset or delay the need for new water supplies to meet growth in these bustling metro areas that represent 20 percent of the country’s Gross Domestic Product and employ 20 million people.

The workgroup’s first task was to set realistic goals. We quickly decided that trying to compare one metropolitan area to another to measure water-savings was unrealistic. Here are some reasons why.

  • Lack of data: The workgroup found that comprehensive information on conservation and reuse implemented to date is not available. Each of the water providers within the ten metropolitan areas track information about their conservation programs differently. For example, water use in central Arizona is tracked by the state Department of Water Resources based on reports that cities are required to file annually. We have been collecting that data for over 30 years. Most metro areas track their information separately. On top of this, there are no consistent accounting categories or definitions and that makes comparing efforts virtually impossible.

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  • Different Demographics: Differences in median income, size and age of homes, and density of living units within each metro area have an impact on per capita water use. For example, metro areas with higher density housing and more apartments generally have lower water use per capita because the demand for landscaping is less. Those that have a higher percentage of older or rented single-family homes tend to have a higher per capita use than newer, owner-occupied homes.
  • Climate Extremes: Then there is weather. Climate varies significantly across the metropolitan areas. It is easy to see why outdoor water use is high in the Phoenix area, which receives only 7 to 11 inches of precipitation a year and where supplemental irrigation is required year-round. It would be hard to compare that to Denver’s outdoor use, when Denver receives 17 inches a year and landscaping is dormant a good part of that time.

The workgroup's next task was to determine what had happened to water use in the metro areas since 1990 and what could be expected in the future. Here are two of our key findings:

  • The population in most of these metro areas grew over recent decades, but per capita water use has decreased, partially offsetting population growth. For example, the City of Phoenix’s population grew by 47 percent between 1991 and 2013, but its per-capita use rate decreased by 29 percent during that period.
  •  Water providers in these metro areas will continue to increase water use efficiency and reuse. Opportunities will vary depending on many factors, including public acceptance and cost of new water supplies.

As a final task, the workgroup identified potential actions to accelerate conservation efforts in these ten metropolitan areas. These actions include:

  • Increasing outdoor water use efficiency through technology improvements, behavioral changes, and low-water use landscapes.
  • Increasing the customer's understanding of water use.
  • Increasing funding for water conservation and reuse.
  • Integrating water and land use planning.

Last week, Reclamation published the Moving Forward: Phase 1 Report, which includes chapter 3 detailing the workgroup's efforts. It’s not hard to read and is packed with details and charts. It includes 44 case studies of conservation and reuse programs within the ten metro areas. It makes for some of the best reading in the report.

Our next job is to take action. The goal of Moving Forward: Phase 2 is to implement pilot projects based on potential actions identified by the workgroup. I guess it's back to work.

For 46 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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