Calamity on the Colorado

ASKED IN 1995 what the Bureau of Reclamation plans to do when sediment threatens to fill Lake Powell, the 186-mile-long reservoir on the Colorado River, former reclamation commissioner Floyd Dominy replied, “We will let people in the future worry about it.” Lake Powell and Glen Canyon Dam are less than 50 years old, yet already we can see that those who will bear their true costs will not be some generation in a distant future, but our children and grandchildren, and even ourselves.

Glen Canyon was the second of two high dams on the Colorado. In 1936 Franklin D. Roosevelt dedicated the earlier of the pair, Hoover Dam, the first of nearly 50,000 large dams built worldwide, 90 percent of them since 1950. To justify this frenzy of construction, proponents and funders routinely exaggerated benefits and longevity while underestimating and ignoring costs. The most obvious cost of Glen Canyon Dam is the chasm that it drowned, western explorer John Wesley Powell’s “ensemble of wonderful features — carved walls, royal arches, glens, alcove gulches, mounds, and monuments.” These the Bureau of Reclamation sacrificed to fuel the juggernaut of development in Arizona, California, and Nevada. But there are other costs.

The dam not only drowned Glen Canyon, it radically changed the Colorado River downstream in Grand Canyon. Before the dam, the river was so muddy that the pioneer explorers joked (as they did about many free-running Western rivers) that it was “too thick to drink and too thin to plow.” The Colorado delivers enough sediment to Lake Powell to fill 1,400 ship cargo containers each day. The dam traps it all, leaving the water below clear as air and starving plant and animal species in Grand Canyon of the sediment they need for habitat and spawning.

Spring snowmelt once swelled the unimpeded river to 100,000 cubic feet per second (cfs) or more, equal to the summertime flow of Niagara Falls. In midwinter the flow dropped to only a few thousand cfs. To meet the demand for power in the Southwest, dam operators smoothed out the seasonal variations while they drastically increased the hourly ones, the released water surging through Grand Canyon like mini-tsunamis, washing away what sediment there is.

We justify dams for the hydropower, flood protection, irrigation water, and recreation that they provide. Yet over time, accumulating silt reduces and then eliminates each benefit. As long as the laws of physics hold, large reservoirs must fill with mud. After Lake Powell fills, the Colorado River will meander across a mud flat and plunge down the face of Glen Canyon Dam in a waterfall that will undercut and eventually collapse the dam. In time, the river will remove the dam debris and lake sediments as though they never existed. Dams imprison rivers, but eventually they annihilate their jailers and escape. Like the truth, a river will out.

Scores of the world’s smaller reservoirs have already filled with mud, or nearly so. Matilija and San Clemente Reservoirs in California, China’s Sanmenxia, and others are full and overflowing. The U.S. Army Corps of Engineers estimated the life of the Cerron Grande Dam in El Salvador at 30 years, less than one-tenth the preconstruction prediction. A mid-1980s study for the World Bank found that world reservoirs contained 1,100 cubic kilometers of sediment, nearly a billion acre-feet and almost one-fifth of worldwide storage capacity.

Lake Powell is so large that it will take longer to fill with sediment than most reservoirs — but how long? Assuming that sediment continues to arrive at the rate calculated from sonar surveys in the 1980s, to fill Lake Powell’s 27 million acre-feet would take 700 years (an acre-foot equals about 326,000 gallons). But that time span is certain to be a drastic overestimate. Many scientists predict that within two decades, rising demand for Colorado River water and falling supply will drop the surface of the reservoir to its lowest level, known as “dead pool.” Because the lowest exit from the dam (the river outlet works) is 237 feet above the original riverbed, at dead pool Lake Powell will still hold 2 million acre-feet of water, one-thirteenth of capacity.

All things being equal, to fill a Lake Powell of 2 million acre-feet with sediment will take not 700 years but about 55 years. And all things won’t be equal.

Lake Powell is destined for dead pool for two reasons: First, because the Southwest already consumes the entire flow of the Colorado River, and demand still rises inexorably. Some of the driest states — Nevada, Arizona, and Utah — are among the fastest growing and none plans to slow down. Take a desert, add water, stir in money — that will continue to be the Southwest’s definition of success until it fails, until whole subdivisions stand empty because they have no water.

Second, while rising population drives demand for water in the Colorado River Basin, climate change shrinks supply. Since 1950, the average temperature in the West has risen over 2°F, nearly twice the global temperature rise during the entire twentieth century. Higher temperatures increase evaporation, which reduces runoff. But calculations show that runoff falls by an even greater percentage than temperature rises. Suppose that evaporation in the Colorado River Basin increases by 2 percent, while precipitation remains the same. Then runoff declines by 14 percent. If precipitation also declines by, say, 1 percent, then runoff drops by 22 percent. How much water is 14 percent of the average flow of the Colorado River? Two million acre-feet, nearly half of the water California takes from the Colorado every year.

A 14 percent decrease in the flow of the river is in the middle of the range that climate models project. Not a single climate study projects an increase in flow. The more pessimistic projections may already be coming true: from 2000 through 2009, inflow to Lake Powell was down by one-third.

Lake Powell’s decline has created a vicious cycle that will reduce its life span even further. You can see the effect as you raft through Cataract Canyon above Lake Powell, where the lowering lake level has exposed thin strata of silt from the reservoir’s formerly submerged delta. Before your eyes, the sandy layers crumble and fall into the river, which washes them down into the lake and deposits them anew. Lake Powell thus gains not only the new sediment that the Colorado River brings to it, but the recycled, older sediment that the river deposited years and decades before. The reservoir also gains recycled sediment from its muddy tributaries: the San Juan, the Dirty Devil, and others. A recent sediment survey found that in five years of declining water levels, Lake Powell received 22 years’ worth of recycled sediment. Thus even the 55-year estimate of the reservoir’s longevity might be too high.

With demand rising and supply falling, Lake Powell could reach dead pool in the 2020s. Impossible? Hardly. Between 1999 and 2005, the reservoir lost two-thirds of its volume and neared the elevation of its generator intakes, 333 feet above the riverbed. Another two or three years at the same rate of decline and Lake Powell would already be at dead pool. Fortunately, a wet 2005 intervened to offer a temporary reprieve.

Another threat from rising sediment is invisible to our eyes but may be the more dangerous. The delta at the reservoir’s north end is one of two sediment deposits on the floor of Lake Powell. A second, smaller wedge has piled up against the dam’s upstream face, the result of turbidity flows racing along the bottom of the reservoir. The sediment wedge at the dam face will rise gradually until it threatens to block the outlet works. Former Reclamation scientist Dave Wegner of the Glen Canyon Institute and former Commissioner Dominy (who died in April) proposed drilling new tunnels below the dam, through the sandstone bedrock, and up through the floor of the reservoir, allowing water and sediment to bypass the outlet works. Would it work? No one knows, for no one has studied the possibility. But since the sediment will never cease to arrive, the tunnels, or any other solution, could never take a holiday.

Moreover, instead of accumulating steadily from small turbidity flows, a large volume of silt could arrive at the dam face all at once. A vast quantity waits suspended not only in Lake Powell’s delta, but in deposits along the river’s upstream tributaries. An earthquake, or an unusually large storm or series of storms, could set this silt moving along the lake floor and up the dam face.

If the surface of the reservoir were below the openings to the generators when silt rose to block the outlet works, no water would be able to leave Glen Canyon Dam and enter Grand Canyon. The tributaries in Grand Canyon add too little water to make up for the loss of the mainstem, so sections of the river would run dry and riverine life would die. These conditions would persist until water rose high enough in Lake Powell to exit either through the disused generator intakes or the spillways near the crest of the dam.

As long as Glen Canyon Dam prevented mainstem water from reaching the Grand Canyon, only a trickle from the tributaries in the canyon would arrive downstream at Lake Mead. To meet downstream water contracts, the Bureau of Reclamation would have to drain Lake Mead to dead pool within a few years. Until the Colorado River flowed again, evaporation would drop Lake Mead even lower and no water would be able to leave Hoover Dam. As long as neither dam could release water, the lower Colorado River would cease to exist.

Though every dam will fill with silt eventually, reclamation agencies design them to hold water, not mud. Wet mud weighs roughly twice as much as an equal volume of water. The area behind Glen Canyon Dam has room for 70 billion tons of sediment. Would the dam hold that much? No one knows. Will the weight trigger an earthquake that precipitates a sediment flow or collapses the dam? No one can rule out the possibility.

The epicenter of the May 2008 earthquake that killed 70,000 people in China’s Sichuan Province was located 3.5 miles from Zipingpu Dam, which itself stands 550 yards from a fault line. Completed in 2006, Zipingpu had not had time to fill with silt, but did hold 315 million tons of water. The earthquake cracked the dam, requiring the Chinese authorities to drain the reservoir. Some seismologists believe that though the weight of the water did not cause the earthquake, it likely advanced its timing and increased its severity. Geologists have long known that reservoirs trigger tremors. In the decade after Hoover Dam went up, some 600 earthquakes struck the area.

If Glen Canyon Dam were to fail when Lake Powell was full of mud, or even half full, one of the great disasters in United States history would unfold rapidly. Sludge would destroy the Colorado River ecosystem in Grand Canyon. The arrival of the silt from Lake Powell might overload Lake Mead and topple Hoover Dam. As the silt continued its way downstream, it could collapse the other Colorado River dams and even reach the Sea of Cortéz. Repair would be so monumental and costly as to be impossible. The Colorado River dams provide water and power to 30 million people; without them, the economy of the Southwest would collapse.

The benefits of large hydropower dams are fated to fade and disappear, in some cases in spectacular fashion. The hundreds of dams that have destroyed rivers across the West represent a kind of national debt that Dominy’s “people in the future” must someday pay. In this century of climate change, that debt is coming due far sooner than anyone imagined.

James Powell serves as Executive Director of the National Physical Science Consortium. Presidents Reagan and George H. W. Bush both appointed Powell to the National Science Board, where he served for twelve years. Asteroid 1987 SH7 is named for him. He has authored six books.

Peter McBride is a native Coloradan who grew up on a cattle ranch. He has traveled to more than sixty countries on assignment for National Geographic, Smithsonian, Esquire, Men’s Journal, Outside, and others. He lives in Basalt, Colorado, where he serves on the town council.


  1. Yey, can hardly wait to see that monster come down. I hate that damn dam. Long live Hayduke. Take it down now!!

  2. Wow, a sobering reminder of how short our vision can be.

    Respect and learn from nature and the forces of this world, or learn to regret it.

    Well written, thank you.

  3. Despite the concerns of a few, as a nation we still still work under the flawed, and eventually fatal assumption, that growth is good. Describing “behind the scenes” details, as this article does so well, helps spread the good word.

  4. Might Lake Powell not just fill up with silt and become a marsh with a river running through it, one that then flows over the edge of the dam? Then it could slowly eat away at the dam and eventually we’d have a free river again, at least for that stretch?

    I must admit, I love the disaster scenarios; it’s a great appeal of environmentalism for me. But I fear it will all end far less spectacularly.

  5. Great photos in the video segment. The lack of actual research in your article, however, is astounding. At some points, your article seems to have been taken over by some evil scientist who wishes for civilization to come tumbling down. Must everything be catastrophic, to those in the media? Won’t the dam’s evolutionary process be gradual, with scientists first sounding Lake Powell for survey maps, and presenting their findings and projections to State and Federal officials? You should read “Colossus” by Michael Hiltzik if you wish to become truly familiar with how wonderful things were when the Colorado River ran freely to the Gulf of California, or cut through the desert southwest to form the Salton Sea. Desert dwellers were terrified of the Colorado River before it was harnessed. I thoroughly agree that the SW population has overwhelmed the Colorado River’s supply, but the silt angle of the story does not work. I would have preferred you focused on the need to revisit the Colorado River Treaty of 1944, to bring the allocations up to date, lowering them from the current 16.5 MAF to the real annual running average of 14.7 MAF.

  6. What a stunning example of the limits to unsustainable development. Because those limits have been ignored, both the environment and millions of people will suffer. Of course, our legal and political system will ensure that the suffering is not distributed fairly.

  7. Still waiting on the math, with which the author claims, will fill Lake Powell with silt.

    For others who doubt, worth reading:

    As for the use of dams, this past month showed the importance of Three Gorges Dam to the people of China, as loss of life from flooding reached close to 1,000 people and an estimated $10B plus in damage.

    Those who know the history of this river, search 1954. Astounding loss of life and property.

  8. Pakistan would certainly have liked to have a regulatory handle on their rivers this past month, as the number of people displaced by floods is now estimated to be 12 million.

    Oh…but that control would take away from the beauty of a raging river. Yeah, I forgot. It’s easier to have someone like Powell make unsubstantiated statements disguised as science.

  9. My bad…14 Million people. Human beings.

    We harness nature to prevent it from killing us. Have you seen people? They’re frail, no outer shell, poor sense of smell, limited vision, lizard brain…all we have is creative thought to protect us.

  10. Bx – Interesting perspective. I, too, love people(though I admit not in general, but specifically). In general? I really believe that people who are so greedy that they will develop settlements(for others) in lands where nature is hostile to such an invasive species should be held accountable.

    Nature WILL seek balance; it’s….well, it’s one of the laws of nature! But people? If we are so damned smart – then why do we still(as a whole) continue to bang our heads against the wall, trying to force dominion over a force which will not be dominated?

  11. @ BXcapricorn
    “It’s easier to have someone like Powell make unsubstantiated statements disguised as science.”
    James Powell serves as Executive Director of the National Physical Science Consortium. Presidents Reagan and George H. W. Bush both appointed Powell to the National Science Board, where he served for twelve years.

    This isn’t a scientific journal. Make fun of the messenger if you wish, but you don’t even use your real name for your blather. Thousands who die in floods and the inconvenience of a wild river will seem a worthwhile trade compared to what’s coming for Tucson, Phoenix, Vegas, LA et al. And for what? The unmitigated greed of a few of the wealthiest among us.

    The irrigation systems of California and Washington are not the great boon they are made out to be, even without taking siltation into consideration. They contributed mightily to the destruction of small-scale agriculture in this country, and we will wish we had those farmers and those family farms (in places where it actually rains) back in production before very much more time passes.

  12. I offer you merely links that prove that having an opinion, like the ones proposed by this organization:

    help impede the development of a series of Pakistani dams. We’re now well beyond the 100,000 displaced people this organization warned of when Tarbela Dam was built. Instead we have a country with 20M people displaced, the fear that 3.5M people will contract cholera, and International aid that cannot possible arrive fast enough. Will the well-meaning people that blocked the efforts of others, ever take responsibility for their actions? I support the cause of protecting this river’s ecosystem but you cannot cherry pick problems, and choose humanity last, each and every time. Sometimes taming a wild river makes the most sense. The dire predictions about SW cities may come true over time, if there is no agreed upon development moratorium, but Lake Powell will not fill with silt in your lifetime, nor your grandchildren’s lifetime. Better to concentrate your thinking in the reality facing Third World countries like Russia, Pakistan, etc.

  13. Your faith in technology to solve all our problems is touching, if contrary to the historical record. While it may be comforting to ascribe our relative prosperity over the past century to our clever little monkey brains, in reality, it’s due to the bounty of cheap energy we’ve lucked into. And now, like the monkey in the parable, we seem to be refusing to open our fists and let go so we can extricate ourselves. Words like hubris and overshoot are appropriate.

    The American southwest is facing huge problems that will surface in our lifetime. How much death and destruction? Depends on how soon we let go of our failed paradigm and start working on real long-term solutions. Given the American public’s turn towards xenophobia and scapegoating, (for a view of where that’s headed you might read Eric Hoffer’s “True Believers,” 1951) it’s unlikely the migrants out of Phoenix and LA will receive warmer welcomes than the Okies did in California.

    Your concern for the people of Pakistan is also touching. But building dams will not help them, as they won’t work as advertised and will send them deeper into debt peonage. Much of their current predicament, which includes the destruction of economic systems that had existed for centuries, and a changed climate that is now drowning them, is due to our past machinations. Supposedly to help them, but in fact all done so the rich could get richer at their expense.

    Your (and Wise Use’s) version of “putting people first,” will result in not much of anything surviving, especially people.

  14. Don’t get me wrong; I despise this dam. But this doesn’t make me want to invent tales about it.

    I’m confused by this line: “All things being equal, to fill a Lake Powell of 2 million acre-feet with sediment will take not 700 years but about 55 years. And all things won’t be equal.”

    OK, but that is at dead pool. I assume if the dam is at dead pool, and filled with sediment, all that water on top of the sediment will be higher then than dead pool level, no?

    That said, I’m not sure I’d trust the “friends of lake powell” for their data.

    I find the discussion here fascinating because it reveals something about the way we argue against things that harm the environment. We cannot ground our arguments in some view of nature that is essentially a “first principle” as it is called in philosophy, a principle that is transcendental, unarguable, an unquetionable given.

    For example, nature does not “seek balance.” For one, balance is a concept we impose upon nature; for two, there are views of nature that challenge the assumption that it seeks balance. Is the process of evolution one of balance? Some would say it is one of repeated destruction, extinction and eradication of what exists. Is the predator prey relationship one of balance? We might think so, since wolves keep bunny populations in check, but does the bunny think of his death as a balancing act? I’d bet not.

    One could easily argue that nature seeks nothing. It is indifferent. You can impose your spiritualities on nature, and pretend “she” is a “spirit” or “mother” or has some god-like force or will.

    Which doesn’t mean that it’s not a shame that ecosystems are damaged and species sent to extinction by the actions of humans.

    Frankly, I like the idea of nature as a force or pure destruction. Let it destroy that hideous dam!

  15. I must differ with c.penders on the matter of balance.

    Life in the natural world is all about dynamic balances. A bunny’s death may not reflect a balance but a living bunny does. Any living thing is an enormously intricate balancing act. It must balance concentrations of an enormous number of molecules in order to stay alive. Each living cell is bounded by an extraordinary elaborate external membrane that balances what the cell takes in with what it expels. Evolution produces species that express an opitimum balance of form and function under prevailing conditions. Homeothermic animals balance their body temperatures as external temperatures change. A healthy ecosystem expresses a balanced competition for matter and energy among members of the community. Predator/prey relationships, viewed over time, represent a dynamic balance in populations.

  16. BxCapricorn: maybe you should read your own links.

    350,000 salmon this year. THat’s great. I must admit.

    “Before dams were built on the Columbia and Snake rivers, the sockeye run is estimated to have been 3 million a year.”

    Richard Morel – Fair enough, but a question: You write:’volution produces species that express an opitimum balance of form and function under prevailing conditions. ”

    Question: what does Optimum mean?

    Then, later: what does “healthy” mean?

  17. c. peders

    Good questions!

    By “healthy ecosystem” I meant a system not imposed upon by unmanageable external forces. For example, a patch of established pine forest or an undisturbed salt marsh.

    As to evolution and optimization, experts tell us that the asteroid impact 65 million years ago changed conditions catastrophically and led not only to the extinction of dinosaurs and many other species but opened a window to the evolution of new species of mammals, a group that could optimize use of the new array of resources and conditions and establish a new balance. Many biologists think that Homo sapiens may not have arisen without that event. In any case, a new repertoire of species evolved that optimized the use of a new conditions and a new menu of available resources. One of those species seems to have gotten too good at it. In that species “ravage” seems to have replaced “optimize” and therein lies the environmental rub.

  18. @BxCapricorn
    I second c. pender’s comment. A record for after the dams were built and we started counting perhaps. But this is just one of 6 runs that used to exist. The others aren’t doing nearly so well. And how many of these are hatchery vs. wild salmon? All fish in the river are not equal when it comes to sustainability and long-term viability of the run.

    As to how is this possible with the river full of dams? The ESA, which is decried for its lack of success and its great economic cost by the GOP in Congress, who want to kill it.

    There have been huge economic costs to building the dams, both in direct expense and lost opportunities and economic activity elsewhere. Learning to run them in a fashion that does as little harm as possible to salmon has increased that price. But there are still other costs for which economists have a much harder time agreeing on a price tag and which we probably don’t fully comprehend to this day.

  19. I read all my links, and it is difficult to watch a population of a fish I love to eat, get knocked down by 90%, but there was The Flood Act of 1960 (and the reason that Act was passed, is worth reading).

    Then there was WWII before that, which prompted the US to harness the Columbia River for the electrical power needed to build planes and other equipment, required to save humanity from tyranny. Hard choice. Defeat tyranny or save fish. The point I was making was that the fish are coming back. Will they ever return to the peak number sited? Probably not. Could Seattle exist without hydroelectric power? Not a chance. Could wind energy replace it? Not a chance. Wind could make some grid penetration, but many of the designs are induction in nature, and are lost during grid disturbances, even on Windy days. Here’s hoping there are a few more Sean Cutler types out there who can find ways around our modern lifestyle, through scientific breakthroughs.

  20. Rereading my last comment I realized I crossed up the Flood Control Act of 1950 and the Columbia River Treaty, which was passed in the 1960’s.

  21. All walls fail. We have externalized out human population growth to the natural world. Now we are so huge a population that there is no more ability to absorb our externalities.
    Ying and yang, every effect has an equal and opposite one.
    Everything is a bell shaped curve. Our civilization is now on the steeper part of the bell curve, going up exponentially to new heights. The needs of our population are beyond easy control, our resources are getting slimmer, and our technology has to make nearly impossible leaps to try keep up with problems that come at us ever faster and ever more urgently. The wastes produced by our “civilization” are not natural ones and do not obey the rules of sustainability on this earth. This will only intensify, as the bell curve steepens.
    A steep bell curve has to have a steep decline as well. At some point the unsustainability of this huge human population will cause a massive population decline. Our excesses will come back to bite us. Our egos will recieve a reality check. After this, the earth will gradually recover once more. We will not be around to see this, but it will happen. To the earth, we are only a brief firework display that is over soon. The earth will move on; it’s time line being infinitely longer than ours..

  22. In 2007 I rowed the Green and Colorado from Green River, Wyo to the Hoover Dam with two colleges. One thing we noticed was that silt move in very punctuated events, not gradually. Flash floods wash silt from the tributaries and move massive amounts downriver in very short time periods. Lower reservoir levels allow the silt to go even further downstream during these events. We were able to run rapids not seen since the dam was first filled. They were washed clean of silt, which was now at the bottom of the lake even closer to the dam. So this is whats happening; the silt is being concentrated closer to the dam with every flood. So I think Lake Powell could fill up sooner than many people think it will.

  23. I haven’t heard the Words “Global Warming” and the fact that we are doing nothing to cut cut co2 the worse case scenario will happen.Bx does not seem interested in the fact that Global warming contributed to the devastation of Pakistan (while Obama kept sending drones).Also Howard Zinn said in fighting Hitler did we really sop Fascism,as proof the WWII was unnecessary.

  24. Okay. We’ve just had ONE wet winter, and because of human engineering, we’ve balanced out 11 years of drought. Lake Mead is up from 1081′ to its current 1118′ and projected to go to 1153′ by Feb 2013. Yet, we hate ourselves (humans) and love chaos (nature).

  25. I can’t wait until that awful dam comes down. God’s creation will always prevail over our mere, flimsy “creations”. Very well written.

  26. Though I fear for the humpback chub, Colorado squawfish, various types of suckerfish and other native species that may not make it through the transition (they’re not doing well now), I say good; bravo, fantastic, halle-friggin’-lujah.
    We effed up, the sooner we accept that the better. Best thing to do would be to admit our mistakes and immediately start to mitigate them by dismantling the dams and work to get the silt back into and through the system with as little disruption as possible (the disastrous flush alluded to in the article).
    Part of this project (mitigating the affects of a previous massive project to rework the ecology of a region. We need to keep that in mind) will be the massive public works project it will take to create sustainable communities in deserts, taking advantage of available resources, such as ssonal monsoons (cisterns), near constant sunlight, and quick thermal fluctuations (very hot days, very cool nights. Buildings can be designed to take advantage of that). The idea of life in the desert southwest must change. It isn’t the midwest or the northeast or the deep south or any of these places, with more heat and less humidity, and golfing in January.
    People need to get beyond that mindset if they want to live there, or anywhere in the SW. Pobably mostly those out there in Los Angeles and the rest of SoCal.

    I hope this happens in my lifetime.
    It is happening up here in Washington on the Elwha, it can happen on the Colorado.
    Release the Colorado, we have better ways to provide energy and water for our communities.

  27. Hey Bx, try 1105 ft for Lake Mead as of July 4th 2013 .

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