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Calls to Rethink the Colorado River’s Iconic Dams Grow Louder

With two major reservoirs on the Colorado River, Lake Powell and Lake Mead, sitting half empty, will a new hydrologic reality be enough to push for big management changes? One conservation group hopes so.

Written by Tara Lohan Published on Read time Approx. 13 minutes
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The Colorado River through the Grand Canyon has been ecologically impacted by the Glen Canyon Dam, prompting calls for a change in strategy that is made more urgent by the impacts of climate change.Tara Lohan

LEE’S FERRY, Ariz. – Tens of thousands of rafters paddle down the Colorado River through Grand Canyon National Park each year, though most don’t scan the Redwall Limestone canyon sides for bore holes around River Mile 39.

But one group of rafters that launched in mid-March was keen to see those holes and the ashy looking sediment piled beneath them. The holes mark the exploratory tinkering of those who were itching to build another dam on the Colorado decades ago. It’s a rare sign of engineering in this remote section of the park known as Marble Canyon, where it is nature’s handiwork that usually takes center stage.

This group of about 30 boaters consisted of graduate students from the University of California, Davis, with expertise in geology, hydrology, ecology and other subjects related to watersheds. On a journey of more than just whitewater excitement, they were enrolled in an ecogeomorphology class, taking a multidisciplinary look at the canyon while rafting through it.

Each night they gathered in a circle to discuss how the canyon has evolved and changed. They recited the stratigraphy out loud – memorizing the layers of rock that started at the put-in at Lee’s Ferry with Kaibab Limestone from 270 million years ago. And then as they rowed deeper and the rocks rose higher, each layer revealed was like rowing further back in time and they called out, Toroweap, Coconino Sandstone, Hermit Shale, Supai Group – all the way back to Vishnu Schist, “the basement rocks,” which formed nearly 2 billion years ago.

They discussed the slow passage of geologic time that each layer of rock revealed but they also contemplated much faster changes that have happened to this ecosystem since Grand Canyon was bookended by the Hoover Dam in 1936 and the Glen Canyon Dam in 1964.

Lee’s Ferry, Arizona, is the dividing line between the upper and lower basins of the Colorado River. (Tara Lohan)

The canyon that they traveled is now a vastly altered landscape since Glen Canyon Dam changed water temperature, volume and sediment load in the river, creating an environment foreign to the one in which native species evolved. For some of these species, the changes have already been too much. A few others, listed as endangered, now cling precariously to existence.

Problems stretch to outside the canyon, where the entire 1,400-mile-long Colorado River, provider to nearly 40 million people, is so overallocated it’s known to be in a “structural deficit” of 1.5 million acre-feet (489 billion gallons) a year. More water is claimed than nature can deliver most years, which has drawn down the bank account of water savings stashed in Lake Powell behind Glen Canyon Dam and 300 miles downstream in Lake Mead behind Hoover Dam.

How to solve the problem is a source of political and legal wrangling that’s been going on for years among the seven U.S. states that share the river and Mexico. And it’s exacerbated by climate change: rising temperatures are expected to further shrink runoff in the basin, tightening the belt even more.

So what’s to be done? The Glen Canyon Institute, a small nonprofit that advocates restoration for Glen Canyon, put forth a seemingly radical plan a few years ago to “Fill Mead First,” which is another way of saying “drain Lake Powell.” It’s an idea that was rebuked by some environmental groups and state water agencies, and dismissed by federal agencies that manage the water resources and dams. It might have stayed that way, but last fall Fill Mead First was given serious scientific examination in a study by researchers at Utah State University, led by John (Jack) C. Schmidt, a watershed sciences professor.

The scrutiny has catapulted Fill Mead First back into Western water discourse and in doing so, it has revealed some key problems in the Colorado River Basin that can’t be ignored much longer.

Even Schmidt admitted that while crazy, the idea in theory was not necessarily bad.

Dam Nation

Lee’s Ferry, Arizona, where the U.C. Davis students began their rafting trip, is known as River Mile Zero in Grand Canyon parlance. As they lined up their gear on the beach – diligently counting helmets and life jackets, while rigging food and gear to their boats – the students straddled an important divide.

When the Colorado River Compact was signed in 1922 it divvied up the river among seven states by splitting the share in two between the upper basin (which includes Wyoming, Colorado, Utah and New Mexico) and the lower basin (consisting of Arizona, Nevada and California).

A line stretching across the river at Lee’s Ferry marks this dividing point between the basins and it is also a point of reckoning. This is where a gauge measures the official flow of the river – and lately it has largely failed to live up to expectations.

But things could have been worse.

Holes in the canyon wall in Marble Canyon are the result of exploration work when officials were considering building a dam here – before this stretch of canyon was part of the Grand Canyon National Park. (Tara Lohan)

The holes in the rock the students saw at River Mile 39 were at the location of one of two proposed sites for a Marble Canyon dam. If built, the dam would have flooded everything this group (and countless others before them) had just passed through – inundating the beaches where they slept; flooding beautiful Redwall Cavern, an eye-shaped limestone amphitheater where they ate lunch; and swamping Vasey’s Paradise, where water springs from the rocks hundreds of feet up and cascades down to the river, providing a faucet of fresh drinking water amid a garden of hanging plants. And it would have slowed the entire Colorado River to a “scenic trickle” through Grand Canyon National Park, where more than 4 million people each year travel to the canyon’s edge to peer into the abyss.

After much public outcry in the early 1960s, the dam proposal was eventually abandoned and the idea forever extinguished when President Lyndon Johnson made Marble Canyon a National Monument in 1969 and the Grand Canyon Enlargement Act annexed it to Grand Canyon National Park in 1975.

To these rafters now, the idea of a dam here seems almost unfathomable. It’s the same thought admirers of Glen Canyon had when their beloved stretch of the river was sacrificed to build Lake Powell, fueling the West’s ambition for cheap power, bigger cities and more farms.

From the moment Glen Canyon was flooded onward, there have been passionate arguments to remove the dam. The project drowned numerous archeological sites, petroglyphs and areas of importance to Native American tribes and submerged what many have called one of the most beautiful canyons in the world, rivaling its downstream neighbor, the Grand Canyon.

For some, there has always been a cultural and ecological reason to restore Glen Canyon, but Fill Mead First gives a scientific reason, according to the Glen Canyon Institute’s executive director, Eric Balken.

Hoover Dam and Glen Canyon Dam were built with the prevailing mindset of controlling the abundance of the river and providing storage for the Upper Basin in Lake Powell and the Lower Basin in Lake Mead. Under current policy the two reservoirs have been managed under a plan of equalization – aiming to keep roughly equal amounts of water in each reservoir.

But lately that equal water level is low – so low in fact that in the next few years Lake Mead could slip below an elevation that would deem the lake in shortage, triggering cuts to water supply for its users, with Arizona figuring to take the biggest hit.

“Let’s rethink this,” said Balken. “Assume you don’t have a full Colorado River anymore, do you really need to have two less than half-full reservoirs? Let’s put the water downstream in Lake Mead and give Glen Canyon a chance to come back.”

The Glen Canyon Institute has devised its Fill Mead First plan in three stages. The first would simply lower lake levels in Powell to the minimum power pool, which would reduce but not eliminate hydroelectric power generation from the dam, and would allow much of Glen Canyon above the dam to re-emerge from the depths. The second stage lowers the water even further to “dead pool,” which would eliminate hydropower generation entirely and expose even more of the upper canyon. And the third phase would involve drilling new river outlet tunnels to allow both water and sediment to bypass the dam, creating conditions that are as close to pre-dam days as possible.

This third stage is the Glen Canyon Institute’s ultimate goal.

The organization posits that, in addition to the obvious benefit of being able to restore Glen Canyon, the proposal could help solve many of the challenges facing the region by creating more available water supply and fixing ecological issues downstream of Glen Canyon Dam.

It almost seems like a silver bullet, said Jeffrey Mount, a senior fellow at the PPIC Water Policy Center in California and an emeritus professor at U.C. Davis in the Department of Earth and Planetary Science. Mount accompanied U.C. Davis students on their Grand Canyon journey and darted between their rafts in his kayak, peppering them with questions about the feasibility of Fill Mead First.

Graduate students from UC Davis journeyed through the Grand Canyon in March 2017 to learn more about how the canyon and its ecosystem have adapted and changed over time. (Tara Lohan)

“Once you start diving into the tradeoffs you can see how wickedly complicated it can become,” said Mount. “For every benefit created there is a tradeoff, reminding us again that there is no complete solution to our problems of water management, whether it’s on the Colorado or anywhere else in the West.”

The most obvious tradeoff would be reducing or eliminating hydropower generation, which provides revenue for some Bureau of Reclamation environmental programs. A study found the impacts to ratepayers and the grid without the dam’s power would both be small, however.

The next point of contention is how much water the plan would free up. According a report commissioned by the Glen Canyon Institute, Fill Mead First could save around 300,000 acre-feet (98 billion gallons) of water each year by reducing water lost to evaporation on Lake Powell and lost to groundwater seepage in the surrounding porous rock. As they point out, this amount is equal to Nevada’s entire share of the river.

But an exhaustive analysis of all the existing data related to Lake Powell’s seepage and evaporation done by Schmidt at Utah State came to a different conclusion, finding that only 50,000 acre-feet a year might be saved, and it could be less with lower reservoir elevation.

When it comes to the third possible benefit – aiding the ecosystem downstream of Glen Canyon Dam, things get even more complicated.

There’s no denying the impacts from Glen Canyon Dam on the Grand Canyon ecosystem are numerous. The dam eliminated natural flows and floods. Water releases now are timed for peak hydropower revenue. The water temperature is a nearly consistent 46F year round, instead of the seasonal range of 35–85F. And around 95 percent of the sediment that once flowed downstream past Lee’s Ferry is blocked by the dam.

Sediment is crucial for river health, carrying nutrients, rebuilding beaches and sandbars and providing in-stream cover in the murky water for native species like humpback chub and razorback sucker whose numbers have tanked since the introduction of nonnative fish like brown and rainbow trout, which like the cold water. Threatened, too, are riparian species on riverbanks like willow, which have been overtaken by pesky tamarisk, an introduced species that has thrived in the post-dam regime.

To combat these problems, federal agencies now employ “adaptive management,” trying to better assess the ecological impacts and shift strategies, like adding occasional high-flow releases to send more water and sediment down the river, simulating more natural floods.

While costly, the efforts have done little to restore endangered fish populations and the high-flow events are more helpful for “rafter habitat,” adding more sand to beaches where boaters overnight during their passage through the canyon.

Fill Mead First’s ultimate stage three plan would ostensibly bring warmer water and more sediment back to the river, but both Mount and Schmidt question whether either would really aid native species at this point. Schmidt’s study succinctly summed up why: “The ecosystem that presently exists in the Grand Canyon segment is no longer dominated by the ecosystem processes that existed prior to 1963.”

While native humpback chub and razorback sucker currently face competition from cold water fish like trout, more warm water would likely mean that another whole crop of introduced fish – like smallmouth bass, which reside downstream in the warmer waters of Lake Mead – would move upstream, replacing one predation problem with another.

And that warmer water would also eliminate the current trout fishery, which is a part of the region’s recreation economy.

Those are just some of the impacts that experts think might occur. Much, much more is not known. Schmidt said Fill Mead First’s impact on the ecosystem would be unprecedented. “There is enormous uncertainty and enormous disagreement among river stakeholders that more natural flow is a good idea,” said Schmidt. “An ecosystem ecologist would tell you it’s an enormous, unpredictable hit on this system.”

Even Balken agrees that it would be a “gigantic alteration to the ecosystem” and said that it would take decades of monitoring and research to get it right.

The confluence of the Little Colorado River with the Colorado River provides an important addition of sediment to the river. After the construction of Glen Canyon Dam, much of the Colorado River’s sediment is blocked upstream. (Tara Lohan)

More Research Needed

In the discussions that the U.C. Davis students had each night during their Grand Canyon trip, there was one recurring theme – for each modern-day problem discussed, like the trout economy versus native species restoration, there were no easy answers.

One of the reasons for that, said Mount, is that agencies like the National Park Service are tasked with goals that are often at odds with each other. Managing for the demands of recreation, hydropower, biodiversity and water supply at the same time has proven an impossible balancing act.

Mount suggested an idea he said some might call heresy – asking the Park Service to specialize more. One way to do that would be to focus protection efforts for biodiversity on the side canyons and tributaries of the Colorado River, where native species are actually already thriving in many places. And then dedicate the mainstem of the Colorado River for the needs of “recreation and inspiration,” which would require curtailing hydropower profits a bit.

Maybe the idea won’t be popular in the larger water community, with so many entrenched views and so much at stake. But there are no really popular answers these days to the West’s biggest water struggles.

“It’s all about tradeoffs and what is more valuable to you,” said Mount.

This is also the heart of Fill Mead First, and Balken doesn’t mind that the idea isn’t widely embraced yet, either.

Balken said his organization’s goal is to get the Bureau of Reclamation to study the idea in more depth. “It’s going to need to be a decision made by all the governors of the basin states, and state and regional water managers. It would have to be studied extensively and it would take time.”

To some extent Schmidt agrees, because his research found that not enough is really known about seepage from Lake Powell into the groundwater and while there are modern, cutting-edge measurements on evaporation losses from Lake Mead, no such studies have been done on Lake Powell for 45 years.

Though Schmidt came to a different conclusion than the Glen Canyon Institute about key figures, like water savings, he did so with a caveat that huge gaps in data exist that merit further study.

“I would say now is definitely not the time to implement [Fill Mead First] because the uncertainties are too large,” said Schmidt. “But now is the time to get the right numbers so that 20 years from now we are not left with big uncertainties.”

And whether water managers and officials like the idea, Schmidt and Balken both believe it needs to be studied because climate impacts alone could lower Lake Powell and pose challenges for the ecosystem and water supply that must be understood anyway.

“They are going to want to have some data to know what they are working with, to have a plan, even if it’s a backup plan,” said Balken. “Regardless of whether any entities want to endorse the idea, the potential downside of not studying it are too big to ignore.”

Schmidt concurs. “What is the effect of [Colorado River] flow being near minimal power pool? Or near dead pool? Those things might happen intentionally or despite our worst fears.”

The worst fears may be a new hydrological reality and it shouldn’t come as a surprise.

Scientist John Wesley Powell (namesake of Lake Powell), who led the first successful expedition down the Colorado River through Glen Canyon and Grand Canyon in 1863 had an inkling, even before climate change.

“Powell was not only the first to explore America’s greatest landscape but also its poet laureate, the first to convey the almost infinite depths of time the Grand Canyon represents,” wrote Edward Dolnick in his book about the journey, “Down the Great Unknown.” “And yet at the same time as he was discoursing on infinity, Powell became the first great spokesman in American history for the notion of limits.”

And those limits in particular related to water. The checkerboard of farms that characterized the East could not be replicated here in the West, Powell understood. It was a position that eventually made him unpopular with the power brokers in D.C.

More than 150 years after Powell, scientists are still traveling in his watery path, trying to understand those limits and to ask the tough questions, however unpopular they may be.

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