Dec 20 2021Share

Arizona a Key Contributor to the Latest Plan to Preserve Lake Mead

By Warren Tenney

Water managers in Arizona, California, Nevada, along with the US Department of the Interior, have agreed to take swift action to voluntarily leave an additional 500,000 acre-feet of water in Lake Mead in 2022 and 2023. This commitment, labeled as the 500+ Plan, is another significant effort to prevent Lake Mead from dwindling to critically low levels. With Lake Mead being only a third full, all parties understand the seriousness of the Colorado River conditions, which is why they worked diligently to rapidly pull together the 500+ Plan within only four months.

COR LevelsThe reality is that the Colorado River is under stress from an unprecedented drought, impacts of climate change, and over-allocation. Due to these impacts, the Department of the Interior declared the Colorado River would be under a Tier 1 shortage declaration starting January 1, 2022, which requires Arizona to take nearly 30 percent less water. Yet, with Lake Mead going from half full to a third full within only two years, water managers recognized additional action needed to be taken and crafted the 500+ Plan.

To address these concerning conditions, tribal and non-tribal water users from the Lower Colorado River Basin States - Arizona, California, and Nevada - came forward to voluntarily contribute water that would add up to the necessary 500,000 acre-feet of additional water on top of the reductions already agreed upon in the Drought Contingency Plan (DCP) and in a Tier 1 shortage. A financial investment of $100 million for both 2022 and 2023 is to help incentivize some to leave their supplies in Lake Mead. Arizona contributed $40 million for this purpose, with the Central Arizona Project, California, and Nevada each contributing $20 million. The Department of the Interior matched the funding to generate a total of $200 million for the next two years.

Arizona has once again stepped up as a major collaborator in this effort to preserve the River. Along with the financial contributions from the State and CAP, Arizona Colorado River users have opted to leave water in Lake Mead. The Gila River Indian Community and the Colorado River Indian Tribes each made significant water contributions, 129,000 acre-feet, and 50,000 acre-feet, respectively, to enhance Lake Mead’s water storage under this Plan. Arizona irrigation districts along the River also have willingly agreed to take less water from the Colorado River. Additionally, several municipalities have volunteered to leave water in Lake Mead, including most AMWUA municipalities – Gilbert, Glendale, Mesa, Phoenix, Scottsdale, and Tempe – collectively contributing 20,000 acre-feet of water in 2022.

Whether a municipality has agreed to leave water in Lake Mead or not, all AMWUA cities and other municipalities that receive Colorado River water will be impacted financially and thus contribute indirectly to the 500+ Plan. The most immediate impact will be an increase in the delivery rates they pay to the Central Arizona Project. This is because there will be less water delivered through the CAP system, which will affect CAP’s fixed costs. Municipalities had already prepared financially for next year’s Tier 1 shortage, causing a 24 percent increase to CAP’s delivery rates that cities are to pay in 2022. Now the 500+ Plan will drive those delivery rates even higher. While the CAP Board did agree to use $5 million of its tax reserves to cover a portion of this unanticipated rate spike, municipal water utilities will now see a 28 percent, rather than 24 percent, increase in 2022 delivery rates, which means they have to adjust their budgets and forego paying for some vital infrastructure upgrades and maintenance projects.

Amidst the collaborative agreement of the 500+ Plan, scientists and researchers warned that we can only manage demand and that precipitation, temperature, soil conditions are all trending in the wrong direction. This means water managers will have to make decisions and plan in unparalleled uncertainty. Further cooperation throughout the Colorado River Basin will be needed to agree to more holistic, long-term planning. In the meantime, the AMWUA cities and decision-makers in Arizona need to make even wiser and smarter decisions amidst the uncertainty facing the Colorado River.

Lower Basin Reps In VegasLast week at the Colorado River Water Users Association’s annual conference in Las Vegas, the 500+ Plan was officially signed. It was a reminder that while entities in Arizona, California, and Nevada, along with the federal government, have acted and put their cards on the table to safeguard the Colorado River, Mother Nature will play the next hand with this winter’s snowfall and run-off.

To print or save this week's blog, a PDF version is available HERE.

For over 50 years, the 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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