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What does the Colorado River shortage mean for ... water conservation?

Jun 24, 2021

Leading up to the expected Colorado River shortage declaration in August, the Kyl Center for Water Policy at Morrison Institute will be posting information about what the shortage will mean for Arizona communities. This is part one. The rest of the series is available here.

Over the past two decades, the water level in Lake Mead, the huge Colorado River reservoir that serves Arizona, California, Nevada and Mexico, has been declining at a concerning rate. In accordance with an interstate plan designed to mitigate the risk of Lake Mead falling to catastrophic levels, next year Colorado River water supplies will be cut for the first time ever.

  • The biggest cut will be to entities in Maricopa, Pinal and Pima counties that receive Colorado River water delivered by the Central Arizona Project (CAP).
  • The cut amounts to about a third of the water CAP delivers in a “normal” year.

Irrigation Districts in Pinal County will bear the brunt of the cut, because they are have a lower priority to Colorado River water than municipalities and Indian tribes with long-term rights to this water. The agriculture sector is currently the largest user of Colorado River water delivered by the CAP.

Should urban water users step up their water conservation efforts?

  • Municipal demand comprises less than 40% of total water demand in Central Arizona, and Colorado River water makes up only about 40% of that demand. Groundwater, Salt River Project water and reclaimed water make up the rest.
  • Long-term reductions in water use by urban users are helpful because they enable water providers to stretch available supplies to serve more people and businesses. Because over 90% of water used indoors is reclaimed and reused, reductions in water used for outdoor landscaping provide the biggest benefits.
  • While helpful, especially at a local level, reductions in municipal water use won’t necessarily translate into water left in Lake Mead: Junior priority users are entitled and eager to use water that more senior contract holders leave in the system.
Graph showing water use in the Arizona Sun Corridor by sector.

This graph shows the annual water use by sector in the Phoenix, Pinal and Tucson Active Management Areas. (Data Source: Arizona Department of Water Resources)

Graph showing Colorado River water use by sector.

This graph shows annual Colorado River water use in Arizona by sector. (Data Source: Arizona Department of Water Resources)

Check out the links below for more information:

Arizona’s Most Precious Resource: Arizona’s Water Story
Arizona Water Augmentation Concepts
A Joint ADWR/CAP Statement On Colorado River Shortage Preparedness
Colorado River study means it's time to cut water use now, outside experts say
CAP Priority Explainer