On a turquoise lake in a sandstone desert, Ross Dombrowski is trying to figure out what to do about the rock growing behind his houseboat. The rock, spectacular and rust red, like most in southern Utah, wasn't visible below the water's surface when Dombrowski moored his houseboat on Lake Powell last year.

Today, it's three stories tall.

"I would never think it would get to this," he says, looking at the shrinking lake. "But it has."

Despite recent rain and record snowfall in California's Sierra Nevada, the Western U.S. is experiencing one of its driest periods in a thousand years — a two-decade megadrought that scientists say is being amplified by human-caused climate change. The drought — or longer-term aridification, some researchers fear — is forcing water cutbacks in at least three states and is reviving old debates about how water should be distributed and used in the arid West.

At Lake Powell, the nation's second-largest reservoir, record-low water levels are transforming the landscape, renewing a long-standing dispute over the land the reservoir drowned — a canyon labyrinth that novelist Edward Abbey once described as "a portion of earth's original paradise." For half a century, environmental groups and Colorado River enthusiasts have implored water managers to restore Glen Canyon by draining the reservoir.

The goal has always been viewed as a bit far-fetched. Lake Powell is one of the busiest tourist destinations in the country. A half-billion-dollar tourism industry has blossomed on its stored waters along the Utah-Arizona border.

But with water levels at record lows and dropping, hindering tourism and revealing long-hidden rock formations like the one behind Dombrowski's boat, advocates for Glen Canyon see a unique opportunity to catalog what was lost and to correct, perhaps, what environmentalist David Brower called "America's most regrettable environmental mistake."

Human actions built the reservoir. Now human actions are causing it to shrink.

"All of the best data that we have suggests it's going to be mostly empty for now on," says Eric Balken, executive director of the Glen Canyon Institute, a nonprofit that wants to see the canyon restored. "So I think it's really important for policymakers to consider what phasing out this reservoir looks like, because if we don't, then we might just be stuck in a harder situation down the road where it's happening by default."

A critical "bank account" that's overdrawn

It would be hard to overstate the anger sparked by the creation of Lake Powell and the flooding of Glen Canyon. The plot of Abbey's most famous fiction, The Monkey Wrench Gang, centered on a band of environmental extremists hellbent on destroying the concrete behemoth that pinched off the Colorado River near the Utah-Arizona border in 1963.

The Glen Canyon Dam, named for the canyon it drowned, was celebrated as one of the "engineering wonders of the world" by the Bureau of Reclamation. To Abbey, it was "an insult to God's creation."

Rock spires, arches, amphitheaters and ecosystems were gradually submerged. Stalled water crawled up slot canyons. Petroglyphs and pull-tab beer cans were covered over.

"They ruined it all when they put the water in there," says Ken Sleight, a river-runner friend of Abbey's and an environmental preservationist.

The purpose of the dam was to generate electricity for a growing Southwest and to manage flows on the famously up-again, down-again Colorado River. Ranchers, farmers and a fast-growing Western U.S. needed a stable water supply. Glen Canyon Dam and Lake Powell, together with their downstream neighbors, Hoover Dam and Lake Mead, would provide that stability.

"In addition to its significant recreation value, Lake Powell functions as a vast 'bank account' of water that can be drawn on during dry years," states the Bureau of Reclamation.

And it's a big account. At full capacity, Lake Powell holds enough water to flood the entire state of Kentucky a foot deep. The shoreline it creates, in a red rock desert, is longer than the entire U.S. West Coast. But the reservoir hasn't been full for decades.

Hotter temperatures and milder winters have reduced flows on the Colorado River, shrinking nature's annual deposit. Water demands, meanwhile, have remained steady or increased. "To sustain our water use, we have drained the bank account," says Jack Schmidt, a watershed scientist at Utah State University.

Today, Lake Powell and Lake Mead are at about one-third of their total capacity. A chalky bathtub ring stains the canyon walls of both, more than 100 feet overhead.

Federal water officials announced a first-ever water shortage on Lake Mead last summer. The announcement was a recognition "that the hydrology that was planned for years ago — but we hoped we would never see — is here," said Bureau of Reclamation Commissioner Camille Touton.

At Lake Powell, the National Park Service extended boat ramps with steel pipes to sneak boats into receding water. Houseboat rental companies canceled reservations, and federal water managers projected that under a worse-case scenario, Glen Canyon Dam could stop producing power as early as next summer.

Recent snowstorms have improved the short-term picture, boosting snowpack levels across much of the West, but they haven't solved the larger imbalance in the region's water portfolio, which is forcing stakeholders up and down the Colorado River to adapt and think in innovative ways. California, Nevada and Arizona recently reached an agreement to take less water from the river in an effort to prop up Lake Mead.

"This is a wake-up call for everyone," Adel Hagekhalil, general water manager for the Metropolitan Water District of Southern California, told KUNC. "For all of us. We are facing a new normal when it comes to climate change."

A push to revive a storied canyon

In parts of Glen Canyon, the new normal is starting to look a lot like the old.

Slot canyons, grottoes, cliffs and spires — the kinds of natural features that draw millions to Grand Canyon and Arches National Park — are reemerging from the waters. Willows and cottonwoods are sprouting on muddy banks. Pottery shards dot shorelines.

"The last time this span was out, Neil Armstrong hadn't walked on the moon yet," the Glen Canyon Institute's Balken says, steering a boat under one of the largest natural bridges in the world. Water reflects on its red belly like a kaleidoscope as Balken putters up the narrowing canyon ahead.

"Normally, we'd have to park the boat on the other side and hike around," he says. "I can't believe we're doing this."

For the last 25 years, Balken's nonprofit, the Glen Canyon Institute, has been one of the loudest advocates for America's "lost national park." It calls for restoring the canyon by lowering Lake Powell and for a broader rethinking of the values assigned to this stretch of desert.

"This place is so much more than a storage tank," Balken says, walking up a sediment-laden slot canyon. "That's what this [drought] is showing us. These places can recover."

An hour's walk up the canyon, the bathtub ring still stains the wall high overhead, and the floor is covered in shoulder-high vegetation. A narrow stream trickles down, beaver tracks pressed in the mud along its edge.

Biologists and other researchers have joined Balken on similar hikes to document the recovery and see how the canyon is recuperating. Invasive species like Egyptian saltcedar are flourishing alongside native plants. Sediment, deposited by the reservoir's slack water, clogs canyon floors. But life is flourishing the farther away you get from the lake's edge.

The Glen Canyon Institute wants that to continue. It's pushing a policy called Fill Mead First, arguing that when the Western U.S. gets another big snow year, water managers should fill the bank account at Lake Mead before adding water to its upstream backup, Lake Powell.

"I just want to bring, like, every water manager and everybody that's negotiating the future management of Lake Powell and Lake Mead, and I want them to come in and experience this," Balken says. "And just know that when you're talking about refilling Lake Powell reservoir, potentially, you're talking about redrowning this place."

Schmidt, the watershed scientist at Utah State University, did a technical assessment of the Fill Mead First proposal in 2016. He found that its effects on water savings along the Colorado River would be negligible and that it would restore more natural fluidity in the Grand Canyon. But, he says, it doesn't solve the underlying problem of the region's water shortages.

"It doesn't matter whether water is stored in Powell, in Mead, 50-50. It doesn't matter for solving the problem of the imbalance of the checking account," he says. "That problem can only be solved by reducing consumptive use."

The cutbacks recently announced by California, Nevada and Arizona are a first step. But what happens if unusually hot temperatures and low snowpack persist?

"Whatever strategy is used is going to immensely change the world that is," Schmidt says. "Something is going to change, and we better start talking about it."

"It's happening"

While water managers debate that change at increasingly urgent conferences, the conversation about Lake Powell's future is already happening on its shrinking shores.

Lake Powell Marinas, a boat rental company on the reservoir, is advertising for people to come see the natural features revealed by the lower water levels. The mayor of Page, Ariz., a town built for and by Lake Powell, is talking publicly about a reenvisioned future. Houseboaters like Dombrowski are debating whether to sell or hold.

"I've floated all these rivers in the West, and I mean, I would have loved to have been down here before they put the lake in," says bass fisherman Mark Edwards. "And I would have fought against it. But it's too late now."

To Balken, the effort to drain Lake Powell has often felt like "Don Quixote, tilting at windmills," he says. "People thought we were crazy."

Standing on the canyon floor at the base of the aptly named Cathedral in the Desert, he gestures to a crescent of sunlight slanting across a growing canyon wall.

"But look," he says. "It's happening."