In the past 10 days, both Lake Mead, on the Arizona-Nevada border and Lake Powell, roughly 300 miles northeast on the Utah-Arizona line, have recorded their lowest water levels since the reservoirs were first filled.

Lake Mead, the nation’s largest reservoir, supplying water to Nevada, Arizona and California, measured 1,040.4 feet above sea level on Aug. 7. The level has continued to drop since then.

On Monday, the reservoir measured 1,039.83 feet above sea level, nearly 190 feet below full and down about two feet over the past 30 days. A year ago, Lake Mead stood at roughly 1,054 feet.

Hoover Dam, which created Lake Mead, was built in 1935. The reservoir was last at full in 1983.

If the reservoir loses another 4.76 feet, Hoover Dam begins to lose its ability to generate significant hydropower. At 895 feet, it reaches dead pool or complete shutdown of Hoover’s hydropower system.

Lake Powell, the nation’s second largest reservoir and the water bank for Colorado, New Mexico, Utah and Wyoming, reached its lowest point in history on Sunday, at 3,519.8 feet above sea level. A year ago, it was at 3,551.33 feet above sea level. Glen Canyon Dam, which created the reservoir, was constructed in 1966.

The last time Lake Powell was close to full was in 1999.

At 3,490 feet, Glen Canyon Dam begins to lose its ability to generate hydropower. At 3,370 feet, the elevation known as dead pool, hydropower production would stop entirely.

Both reservoirs are fed by the Colorado River, which has been hit by a thousand-year megadrought that has cut its supply from around 15 million acre-feet per year to 12 million. The 2022 study attributes 42% of the drop in river water levels to climate change.

One acre-foot equals about 362,000 gallons of water — enough to supply two families of four for a year.

J.B. Hamby, chairman of the Colorado River Board of California, told PBS last week that three-quarters of the population of the Colorado River Basin, some 30 million people, are directly impacted by risks to Lake Mead.

The seven states on the Colorado River, under the 1922 compact and subsequent agreements, still legally count on 15 million.

Nobody’s getting what the compact promised anymore. The compact allows both the upper and lower basin states to each take 7.5 million annually, or 15 million over 10 years. 

The four states of the upper Colorado River Basin have historically taken far less than they’ve been entitled to, about four million acre-feet annually. 

Historically, the Lower Basin states have used about a million acre-feet more than their formal allocations, largely to cover evaporation and other system losses.

That era is ending. The three states have now agreed to reductions, with Arizona taking the largest cuts because it holds the most junior water rights.

Solutions to the crisis on the Colorado River have been elusive. The seven states had two years to reach an agreement on how to manage the river, with the lower-basin states advocating cuts to the upper-basin states’ water allotments. The upper basin states point out that they already take less water than allowed under the current agreements and cannot cut any further.

That agreement was supposed to be in place by Oct. 1 of this year. But the upper- and lower-basin states fought without reaching a resolution, leaving it in the hands of the U.S. Bureau of Reclamation, which has been without an executive director since President Donald Trump took office in 2025.

That’s left negotiations to Secretary of the Interior Doug Burgum, who has met with the seven governors several times but has come up empty-handed.

Last month, the Interior Department announced its own plan, known as a final environmental impact statement (FEIS), which drew criticism from just about everyone involved in the negotiations.

Arizona Gov. Katie Hobbs, in a statement in July, said the FEIS contains “unacceptable options that include the federal government forcing Arizona to take the majority of draconian water cutbacks.”

However, she added, “implementing the Lower Basin agreement would protect Arizona from massive water cuts, distribute reductions more fairly across the Lower Basin States, and provide stability and protection to the water supply that our communities rely upon.”

Becky Mitchell, who negotiates on behalf of Colorado with the Upper Colorado River Commission, commented in June that the FEIS’ requirement that operation guidelines be renegotiated about every two years would be “incredibly difficult.”

Anne Castle served as the chair of the Upper Colorado River Commission from 2022 to 2025; before that, she was assistant secretary for water and science at the Interior Department during the Obama administration.

For Lake Powell, Castle said it’s concerning “that we’ve used up our storage buffer and allowed the reservoir to get this low.”

As to the Interior Department’s plan for the river, she explained: “The harshest measures contemplated are necessary because of where the reservoirs are and the hydrology we’re dealing with.”

It’s particularly concerning for the lower-basin states, she added. The only mandatory shortages contained in the FEIS are on those states, because the Interior Department is the designated manager for all water delivered below Hoover Dam. 

The department doesn’t have that same authority over the upper basin states nor over Lake Powell.