by L. William Staudenmaier

The Colorado River is a critical water source for more than 40 million people, vast agricultural operations, numerous industries, and a wide variety of ecological resources across the seven states that share its waters: Arizona, California, Nevada, Utah, New Mexico, Colorado, and Wyoming.  The River is regulated by the United States Bureau of Reclamation pursuant to a complex body of statutes, court opinions, contracts, and an interstate compact, collectively referred to as the “Law of the River.”  While The Bureau relies on the Law of the River to determine how to allocate water among the seven Basin states, one thing the Law of the River does not control is the amount of water available to be allocated in any given year.  Among the factors that influence the amount of available water, the overwhelmingly most important factor is precipitation in the Basin.  And for most of the past 23 years precipitation has been substantially—and sometimes vastly—below normal.  The consequences of this long-term drought are now manifesting themselves in ways that were considered highly unlikely just a few years ago. 

Over the past century, the federal government has constructed a robust system of reservoirs throughout the Colorado River Basin.  These reservoirs capture and store runoff from precipitation until it can be released to downstream water users.  The two largest reservoirs, Lake Mead and Lake Powell, have a combined capacity of more than 50 million acre-feet.  This is more than three years of collective “normal” year water apportionments for the Basin states.  Those apportionments, totaling 15 million acre-feet per year, were established in 1922 when the states negotiated the Colorado River Compact.  Through a separate 1944 treaty, an additional 1.5 million acre-feet were committed to Mexico.  These apportionments were based on what we now know was a period of unusually high precipitation in the early 20th Century. 

Today, armed with greater knowledge of long-term hydrology in the Basin, water managers realize that the original water apportionments were wildly optimistic.  Excluding the high precipitation period in the early 20th Century, average annual flows in the Basin have been significantly below the totals apportioned in the 1922 Compact and 1944 treaty.  Moreover, analysis of paleoclimatic data spanning hundreds of years (e.g., tree ring studies) has identified numerous droughts lasting 15 to 20 years at a time.  During these extended droughts, flows in the Colorado River Basin have been even more dramatically below the amounts allocated in 1922 and 1944.  That reality is hitting home throughout the Basin as a result of the current extended drought.

The most recent three years have yielded a total of just 52% of  the average annual water flows over the past three decades, including a low of only 37% of the 30-year average in 2021.   These most recent three years of severely low flows, following two decades of persistent drought, have decimated water storage in both Lake Powell and Lake Mead.  Lake Powell is currently projected to have just 5.6 million acre-feet, 23% of its storage capacity, by the end of this calendar year, while Lake Mead is projected to be down to 6.91 million acre-feet, or 26% of its capacity. 

To their credit, the Basin states and the Bureau of Reclamation have been working together to address the worsening impacts of this drought.  Efforts to date have included a series of agreements, collectively known as the “Drought Contingency Plan” or “DCP,” by which the Basin states agreed to voluntarily reduce their consumption of Colorado River water to keep more water in the reservoirs.  These voluntary reductions (including contributions from Mexico) have collectively conserved more than 4 million acre-feet, keeping water levels in Lake Mead approximately 70 feet higher than would otherwise have been the case.  Despite these efforts, however, the Bureau of Reclamation was forced to declare the first-ever water shortage in the Colorado River Basin for 2022.  This shortage declaration resulted in even more reductions in water deliveries to Basin states under the terms of the DCP agreements.  It also prompted the Lower Basin states (Arizona, California, and Nevada) to develop an additional plan for even greater voluntary reductions.  This plan was called the “500+ Plan” to denote the fact that the states agreed to make at least another 500,000 acre-feet of reductions each year in 2022 and 2023.

On top of these efforts in prior years, the Basin states and the Bureau took additional steps earlier this year to further protect Lake Powell.  First, the Bureau will release an additional 500,000 acre-feet of water from Flaming Gorge Reservoir in Wyoming to increase water levels in Lake Powell.  In addition, the Lower Basin states jointly requested that 480,000 acre-feet of water that would otherwise have been released from Lake Powell be retained there to help protect critical water levels in the reservoir.

Despite these extraordinary voluntary efforts, water levels in Lake Mead and Lake Powell have continued to deteriorate.  Conditions have become so dire that the Commissioner of the Bureau of Reclamation, Camille Touton, recently testified to a United States Senate committee that much greater reductions will be required to stabilize the system and avoid catastrophic declines in water elevations in the two reservoirs.[1]  She indicated that between 2 million and 4 million acre-feet of additional reductions (beyond the already implemented voluntary reductions) will be required in 2022 and 2023 to protect the reservoirs from falling to critically low levels.  Commissioner Touton expressed her hope that the Basin states and the Bureau could work together in partnership to come up with the necessary steps to protect the system.  In response to questions from the committee, Commissioner Touton stated that the Bureau will do whatever is required to protect the system, including unilateral action if the Basin states cannot agree on an adequate plan.  She then indicated that the Basin states should submit proposals for additional voluntary reductions no later than mid-August to provide adequate time to implement necessary strategies.

Shortly after Commissioner Touton’s testimony, the Bureau of Reclamation issued a “Request for Input on Development of Post-2026 Colorado River Reservoir Operational Strategies for Lake Powell and Lake Mead Under Historically Low Reservoir Conditions.”  87 Fed. Reg. 37,844 (June 24, 2022).  The Bureau indicated its intention to begin formal environmental reviews to establish future operating criteria for the Colorado River Basin.  It requested feedback from all interested stakeholders at the outset of this process.  The Bureau specifically noted that

Lake Powell and Lake Mead face extraordinary risks over the next 12-24 months, and … additional actions are needed to protect the reservoirs from rapidly declining to critically-low elevations; reductions totaling millions of acre-feet in reductions of use across the Basin could be needed to stabilize the reservoirs.

Id. at 37,885.

With these stark warnings, the Basin states have begun the process of developing proposals to address the necessary reductions in water use.  In Arizona, both the Director of the Arizona Department of Water Resources (ADWR) and the General Manager of the Central Arizona Water Conservation District (CAWCD), which operates the Central Arizona Project (delivering approximately half of Arizona’s annual Colorado River entitlement to water users in central Arizona), quickly issued statements supporting Commissioner Touton’s call for collaborative action.[2]  ADWR and CAWCD subsequently began briefing water users in Arizona.[3]  As we enter the month of July, rapid progress in identifying options for further reductions will be essential.  Consultations among the Basin states are already underway, but the challenge is daunting.  Undoubtedly, sacrifice will be required from many water users throughout the Basin.  But the risk of not doing enough is so great that hopefully the states will be able to agree on a plan to jointly present to the Bureau.  The next six weeks will be telling. 

[1] Video of the Senate committee hearing is available at

[2] See (statement of ADWR Director Tom Buschatzke); (statement of CAWCD General Manager Ted Cooke).

[3]  See (briefing video); (briefing materials).