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The snow that falls in the Rocky Mountains provides the majority of the water for the Colorado River. But with warming temperatures, drought and increased dust settling on the snowpack, that water source is diminishing. (David Wallace/The Republic)

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With Lake Mead dropping to levels that could trigger water cutbacks in less than two years, there's been a lot of talk lately about negotiating a deal to keep the reservoir from falling even further. 

But in a new report, scientists say the situation is just as worrisome upstream at Lake Powell. 

The declines there during the past 18 years, they say, also reflect the Colorado River's worsening "structural deficit."

The 10 scientists, who make up the Colorado River Research Group, said even though the four Upper Basin states — Colorado, New Mexico, Utah and Wyoming — haven't been using all the water they're legally entitled to, Lake Powell has declined due to extra water releases into Mead.

Those releases, they said, are "the only thing that has kept Lake Mead from dropping into shortage conditions."

"I want people to know that what's going on at Lake Mead is very, very closely tied to what's going on Lake Powell," said Doug Kenney, the group's chair and a professor at the University of Colorado. "We're draining Lake Powell to prop it up."

The scientists titled their report "It's Hard to Fill a Bathtub When the Drain is Wide Open."

Lake Powell now sits 48 percent full, and Lake Mead is 38 percent full.  

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The Colorado River basin, which stretches from Wyoming to Mexico, has been drying out during what scientists say is one of the driest 19-year periods in the past 1,200 years. The river has long been over-allocated, with the demands of farms and cities exceeding the available water supply, and the strains are being compounded by growing population, drought and climate change. 

The scientists, who say their group presents an "independent, scientific voice for the future of the Colorado River," detailed how much Lake Powell has gone down in less than two decades. By the end of this year, Powell's levels are projected to have dropped 94 feet below where the reservoir stood in 2000, when it was nearly full. 

The U.S. Bureau of Reclamation operates Glen Canyon Dam and manages the releases from one reservoir to the other. 

"Continuing this operational pattern will further drain Lake Powell and erode the benefits associated with its water storage," the researchers said in the report. "If storage in Lake Powell cannot rebound in an era where the Upper Basin consumes less than two‐thirds of its legal apportionment, then the crisis is already real."

'Essentially one giant reservoir'

The Colorado River and its tributaries provide water for about 40 million people and more than 5 million acres of farmland from Wyoming to California. 

The legal framework that divides the Colorado River among seven states and Mexico was established during much wetter times nearly a century ago, starting with the 1922 Colorado River Compact. That and subsequent agreements have allocated more water than what flows in the river in an average year, leading to chronic overuse.

For decades, so much water has been diverted from dams all along the Colorado that the river seldom meets the sea. The river's delta in Mexico has become a dusty stretch of desert.

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The river is managed under a system that firmly delineates between the Upper Basin and the Lower Basin, with the dividing line running through Lees Ferry in northern Arizona.

The treaties that originally divided the river allocated 7.5 million acre-feet of water per year for the four Upper Basin states; 7.5 million acre-feet for the Lower Basin states of Nevada, Arizona and California; and 1.5 million acre-feet for Mexico. 

John Fleck, director of the water resources program at the University of New Mexico, recently pointed out in a blog post that the Lower Basin has gotten more water than it is entitled to under the compact — 9.7 million acre-feet of "bonus water" since 2000 — yet Lake Mead is still dropping. 

The scientists suggested that Lake Powell could bounce back better in wet years if "new operational rules" are developed. 

"Better options might be found by thinking outside of this familiar framework. Lakes Mead and Powell, after all, are essentially one giant reservoir," the group said. "Managing — and thinking — of these facilities as two distinct reservoirs, one for the benefit of the Upper Basin and one for the Lower, now seems outdated."

Under the current rules, if Lake Mead's water level reaches elevation 1,075 feet above sea level at the end of any year, the federal government will declare a shortage and supplies to Arizona and Nevada will be cut back.  

Representatives of Arizona, California and Nevada have been discussing a proposed drought-contingency plan under which each state would take less water from Lake Mead to keep it from falling to even lower levels, which would mean even deeper cuts. The four Upper Basin states have been working separately on a regional drought plan. 

The combined amount of water in the two reservoirs has been much smaller since the mid-2000s than in the previous two decades. While the reservoirs' levels have retreated, heavy pumping of groundwater has also led to declining aquifers in parts of the river basin.

Scientists have found that higher temperatures have contributed significantly to reductions in the river's flow since 2000. They call it a "temperature-dominated drought." In one recent study, scientists projected that warming will likely cause the river’s flow to decrease by 35 percent or more this century.

Scientists say status quo 'untenable'

The research group said viewing the river's serious supply-demand mismatch as a problem of the Lower Basin states is too simplistic.

They acknowledged that many stakeholders aren't interested in tinkering with the law or administration of the river, but they suggested "it might be worthwhile to think about what could be achieved in terms of water security, Grand Canyon (and perhaps Glen Canyon) restoration, and other objectives if we allowed ourselves more flexibility in managing (and perhaps modifying) the massive infrastructure investments already in place."

"Long‐term, we may have no choice to consider reform on this scale," they said. 

Some conservationists have long proposed draining Lake Powell and making Lake Mead the primary reservoir.

Jack Schmidt, a professor at Utah State University and one of the group's 10 members, has studied the so-called "Fill Mead First" proposal, which would involve initially lowering Powell to a minimum level at which Glen Canyon Dam would still generate hydroelectricity, and then in later phases draining the reservoir further and eventually drilling new water tunnels around the dam. 

Under the proposal, Lake Powell would become a secondary reservoir to be used only when Mead is full. Lowering the reservoir would reveal the sandstone walls of Glen Canyon and gradually restore a natural river ecosystem in the canyon. Water managers, however, have generally dismissed the idea as unworkable. 

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In a 2016 study of the proposal, Schmidt said there was insufficient data and recommended gathering more data on the losses to evaporation from Powell. After his study was published, the Bureau of Reclamation began a program to measure how much water is lost to evaporation from Lake Powell. 

"I take the position that it does not matter whether water is stored in Powell or Mead," said Schmidt, Utah State's Janet Quinney Lawson chair in Colorado River studies. "We should store water in whatever way minimizes total system losses and maximizes environmental benefit to the Grand Canyon."

Schmidt said Powell and Mead are together "effectively one reservoir" and should be managed as such. "We need to say, 'How do we effectively operate the Mead/Powell reservoir?'"

The group of scientists noted in their report that negotiations on a drought-contingency plan are already pressing up against 2020, when officials are due to start renegotiating the guidelines for managing the reservoirs and dealing with shortages — which are now governed by a 2007 agreement. 

"For many in the basin, the next generation of Guidelines are the place to adopt a comprehensive solution — a sustainable water budget," the researchers wrote. "The new framework can potentially take many forms, but at a minimum, will need to recognize the linked future of the two basins, and the political necessity of addressing equity concerns among users, sectors, and regions.

"Admittedly, this is a tall order on a tight deadline, but the recent history of Lake Powell shows us that the status quo is untenable."

Debates over tapping more water

Despite the concerns about the declining reservoirs, water agencies in the northern states have been pressing for controversial projects to draw out more water. 

In Utah, water districts are proposing to build a 140-mile pipeline to carry water from Lake Powell to growing communities around St. George. 

In Colorado, Denver Water is proposing to expand Gross Reservoir. Conservation groups oppose the project and notified the U.S. Fish and Wildlife Service last week that they plan to sue, saying the enlarged dam would harm trout and violate the Endangered Species Act.

The groups said filling the bigger dam would mean diverting more water out of small streams in the Colorado River basin that are home to threatened green-lineage cutthroat trout. They said the federal agency failed to properly analyze the effects of the project and that drawing out the water from the streams could kill thousands of fish.

The groups include Save The Colorado, the Environmental Group, WildEarth Guardians, Waterkeeper Alliance, Living Rivers and the Sierra Club. They notified the Fish and Wildlife Service, the Interior Department, the Army Corps of Engineers and Denver Water that they intend to sue if the agencies don’t act within 60 days.

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Salt River Project announced in June that water use among its users has decreased by one-third since 1980, even though Arizona's population has doubled since then. Wochit

The environmental groups said if the project goes ahead as proposed, it will further drain the Colorado River. 

Jen Pelz of WildEarth Guardians said in a statement: "People don't love Colorado for our green lawns, but rather our majestic mountains, native trout, and the reinvigorating experiences our wild landscapes and rivers provide."

She said the project would mean "squandering the heritage of our namesake river."

Steve Segin, a spokesperson for the Fish and Wildlife Service, said the agency can’t comment on the pending litigation.  

Jim Lochhead, Denver Water’s CEO and manager, said expanding the Gross Reservoir “will make Colorado’s rivers and environment better off in the future. 

"Delaying this project actually delays environmental benefits, including 1,000 acre-feet of water for rivers and streams in Grand County and an environmental pool with 5,000 acre-feet of water for South Boulder Creek," Lochhead said in an emailed statement. 

He said Denver Water is providing more than $20 million as part of water management efforts "that will result in myriad stream health and habitat improvements."

"We're proud that this project will help us achieve our goals of providing a secure water supply for our customers in the most environmentally sustainable way possible," Lochhead said.

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