Rain, Snow, Have Not Stopped Retreat of Lake Powell

February 20, 2023

The two biggest and most critical reservoirs in the Southwest US are Lake Mead, which is behind the Hoover Dam. and Lake Powell, formed by the Glen Canyon dam. Both have been shrinking radically over the last 2 decades. There’s been talk about whether recent rains and snow might have stemmed that process – but no. One wet year will not be enough.

Inside Climate News:

Water levels in Lake Powell dropped to a new record low on Tuesday. The nation’s second-largest reservoir is under pressure from climate change and steady demand, and is now the lowest it’s been since it was first filled in the 1960s. 

Water levels fell to 3,522.16 feet above sea level, just below the previous record set in April 2022. The reservoir is currently about 22 percent full, and is expected to keep declining until around May, when mountain snowmelt rushes into the streamsthat flow downstream to Powell.

Powell, which straddles the border of Utah and Arizona, is fed by the Colorado River. Warming temperatures and abnormally dry conditions have cut into the river’s supplies, and the seven states that use its water have struggled to reduce demand. That imbalance has dealt an alarming blow to the reliability of water supplies for 40 million people, and is threatening the ability to generate hydropower at Glen Canyon Dam, which holds back Lake Powell.

Even though strong snow and heavy rains have blanketed the West this winter, climate scientists say the severity of a 23-year megadrought means that one wet year won’t be nearly enoughto substantially boost Lake Powell.

Those dropping water levels have spawned a crisis for the Bureau of Reclamation, the federal agency which manages the West’s largest dams, including Glen Canyon Dam and the hydroelectric turbines within. At 3,490 feet, a level referred to as “minimum power pool,” Reclamation may be unable to generate hydropower for 5 million people across seven states. At 3,370 feet, the reservoir hits “dead pool,” at which point water can no longer pass through the dam by the power of gravity. 

At minimum power pool, water would drop below the intakes that pull water into hydroelectric turbines, allowing air pockets to enter the equipment. That could create tiny bursts of air, part of a process called “cavitation,” and damage the turbines.

In response, the federal government has scrambled to prop up the reservoir, resulting in a patchwork of water conservation agreements insufficient to prevent the reservoir from declining. In 2021 the federal government began emergency water releases from other reservoirs upstream of Powell in an effort to protect Glen Canyon Dam infrastructure. Those releases continued in 2022. This winter, Reclamation has been cutting back on the amount of water released from Lake Powell as part of an existing drought response agreement. Those cuts will boost water levels by about ten feet between December and April.

Eric Balken, executive director of the environmental advocacy group Glen Canyon Institute, said Powell would likely be “well below” minimum power pool by now if not for the emergency releases.

“I think decision makers are trying so hard to prop up Lake Powell because they’re really afraid of the infrastructure problems at the dam when it operates below power pool,” Balken said. “That’s what it comes down to. And I don’t think it’s necessarily all about hydropower. I think the dam’s ability to actually release water at low levels is problematic enough that they want to avoid it at all costs.”

Balken and other activists have raised alarm about water levels reaching 3,430 feet. At that point, water would fall below normal intakes, and could only flow through the dam via rarely-used backup pipes near its bottom. The Colorado River’s Upper Basin states have a legal obligation to send a certain amount of water downstream each year.

Those backup tubes, known as the “river outlet works,” were originally meant to be a failsafe or to pass water in high flow years, and aren’t wide enough to carry the legally required amount of water from one side to the other.

With those threats on the horizon, the federal government began a process to reduce the amount of water released from Lake Powell in 2023 and 2024. As it considers a supplemental environmental impact statement to codify those reductions, Reclamation asked states that use the river’s water to provide suggestions on how to spread out the pain of cutbacks.


As of today, the Hoover Dam is still in operation and continues to generate electricity and provide water for irrigation and drinking in the surrounding areas. The dam is considered a critical infrastructure and is maintained and operated by the U.S. Bureau of Reclamation.

It’s worth noting that the water levels in Lake Mead, the reservoir behind the dam, have been fluctuating over the past decades. Low water levels in the lake have affected the dam’s power generation capacity and water supply. However, the dam continues to operate within its normal range of operating conditions, and the U.S. Bureau of Reclamation has implemented measures such as releasing water from the dam’s spillway to maintain the lake’s water levels.

Inside Climate News:

In other nearby mountain ranges, snow totals are between 140 percent and 160 percent above average. Even if those numbers persist until spring, the severity of the Colorado River’s drought means many more years of heavy snow are needed to make a serious dent. 

“It’s great to see a big snowpack,” Udall said. “We would need five or six years at 150 percent snowpack to refill these reservoirs. And that is extremely unlikely.”

A string of wet years is unlikely because of rising temperatures driven by climate change, Udall said. Since 1970, temperatures in the Colorado River Basin have gone up by 3 degrees Fahrenheit. Those higher temperatures have already caused a 15 percent dropoff in streamflows across the region.

Warming has driven a raft of worrying environmental changesacross the region. In recent years, scientists have sounded the alarm about soils drying out. The ground has become parched and soaks up snowmelt before the water has a chance to reach the places where people divert and collect it.

Already, Udall said, winters with 90 percent of average snowpack have led to springtimes with only 50 percent runoff because thirsty soil acts like a sponge.


One Response to “Rain, Snow, Have Not Stopped Retreat of Lake Powell”

  1. rhymeswithgoalie Says:

    This chart reminds me of all the attention I spent on Lake Travis’ water levels in 2011, during the insane Texas drought.

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