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Groundwater Depletion in Colorado River Basin Poses Big Risk to Water Security

An artist’s rendering of the twin satellites of NASA’s Gravity Recovery and Climate Experiment (GRACE). Using data from this mission, scientists have determined that a vast volume of groundwater has been depleted from the Colorado River Basin over the last decade.  Credit: NASA/JPL
An artist’s rendering of the twin satellites of NASA’s Gravity Recovery and Climate Experiment (GRACE). Using data from this mission, scientists have determined that a vast volume of groundwater has been depleted from the Colorado River Basin over the last decade. Credit: NASA/JPL

Let’s step back for a minute and consider the implications of the study released last week on the depletion of groundwater in the Colorado River Basin.

For anyone concerned about the future of the American West, the findings of this study – which was published online in the journal Geophysical Research Letters and conducted by a team of scientists from NASA, the University of California-Irvine, and the National Center for Atmospheric Research in Boulder, Colorado—can make the heart pound.

Let’s start with a little context above ground, before going below.

Lake Mead is the largest reservoir in the United States and the granddaddy of reservoirs on the Colorado River.  This giant man-made lake, formed by the construction of Hoover Dam in the 1930s, can hold nearly two years of the Colorado River’s historic flow.

Some 40 million people – including those in Las Vegas, Los Angeles, Phoenix, Tucson and San Diego — and 4 million acres of farmland rely on water from the Colorado River Basin, much of it stored in Lake Mead.

In 2000, Lake Mead was just about full.  Then a drought hit that has more or less continued to this day.   This has been the driest 14-year period in the Colorado Basin in the last 100 years. Demand for the Colorado River’s water by the seven US states and Mexico, which share the river, now exceeds the ten-year average supply.

As a result, the level of Lake Mead has steadily dropped.  At full capacity, the lake’s level is 1,221.4 feet above mean sea level.  Today its level is at 1,080.9 feet, the lowest it has been since 1937, just after the completion of Hoover Dam.

The now-famous white bathtub ring around Lake Mead’s perimeter tells this story.

Because the lake is shaped like a coffee filter –wider at the top and narrower at greater depths – a seemingly small decline in water level represents a disproportionately large drop in the volume of water it’s storing. Today, instead of holding two year’s worth of Colorado River water, the lake holds about 9 months worth.

Water managers and officials have known for at least four decades that when surface supplies became scarce in the basin, farms and cities would turn to groundwater to meet their water needs, especially during times of drought.

But with groundwater management left to the states, there has been no overarching assessment of what’s happening to water underground – nothing equivalent to Lake Mead’s bathtub ring to signal a problem for the basin as a whole.

Until now.

The white “bathtub ring” of mineral deposits marks the decline of Lake Mead, which is able to store two years of the Colorado River’s historic annual flow.  It currently holds only 9 months worth of that flow.  Photo courtesy of US Bureau of Reclamation.
The white “bathtub ring” of mineral deposits marks the decline of Lake Mead, which is able to store two years of the Colorado River’s historic annual flow. It currently holds only 9 months worth of that flow. Photo courtesy of US Bureau of Reclamation.

Thanks to a NASA satellite mission called the Gravity Recovery and Climate Experiment, or GRACE, which began in 2002, we are getting a look at changes in water storage both above and below ground in watersheds around the world.

Using twin satellites, the GRACE mission measures the mass of the earth over time and space.  Because changes in water storage result in changes in mass, GRACE provides fairly accurate estimates of water depletion over time.

When Stephanie Castle of the University of California-Irvine and her colleagues analyzed GRACE data for the whole Colorado River Basin over the period December 2004 – November 2013, what they found stunned them: the Colorado Basin had lost nearly 53 million acre-feet of water (65 billion cubic meters) – equivalent to two full Lake Meads.

Even more striking, 77 percent of that loss – some 41 million acre-feet – was water stored underground.  That’s enough to meet the home water use of the entire US population for eight years.

(An acre-foot is the volume of water that would cover an acre of land one foot deep. It equals 325,850 gallons, roughly the amount eight people in the U.S. would use at home in a year.)

“We don’t know exactly how much groundwater we have left, so we don’t know when we’re going to run out,” Castle said in a press release announcing the study.

“This is a lot of water to lose. We thought that the picture could be pretty bad, but this was shocking.”

Now, it’s common for farms and cities to pump more groundwater during droughts in order to make up the gap between supply and demand.  The assumption is, that during times of surplus, the groundwater basins will fill back up. 

“This is a lot of water to lose. We thought that the picture could be pretty bad, but this was shocking.” — Stephanie Castle, lead author of the study.

But what if they don’t re-fill?

Some groundwater basins do not receive much recharge even in wet times. I wrote last week about how drought is leading farmers to pump more heavily from the Ogallala Aquifer beneath northwest Texas, a largely irreversible loss of groundwater.  Areas of similar “non-rechargeable” aquifers also exist in the Colorado River Basin.

In addition, virtually all the climate models indicate that the Southwest is in for hotter and drier times, meaning more losses to evaporation, less replenishment of aquifers, and higher water demand from farms and cities.

Jay Famiglietti, senior water scientist at the NASA Jet Propulsion Laboratory, Earth systems science professor at UC-Irvine, and a co-author of this study, pointed out in his post in Water Currents last week that during the severe drought of the past decade, Colorado Basin water demands have outpaced supplies by as much as 30 percent, with groundwater filling the gap.

By focusing only on the drop in Lake Mead and paying too-little attention to the drop in water levels underground, we have placed the West’s water security in serious jeopardy.

Imagine having a bank account for which  you don’t know (1) how much money is in the account, (2) how much gets withdrawn, or (3) how much will get deposited, or when.

Such a money-management circumstance would offer little hope of keeping a family fed, clothed and sheltered over the long term, much less of sending a child to college.

So, we have two choices: continue flying water-blind into the future and leave the consequences to the next generation, or get our heads out of the sand and take action to monitor, manage and balance our water books.

If we choose the second option, what’s needed is fairly clear.

First, conservation and efficiency improvements in homes, businesses and, especially, on farms – which account for some 80 percent of water consumed in the basin – remain the most cost-effective, environmentally sound ways of meeting our water demands.  While we’ve made some solid gains, we have a long way to go and many solutions yet to tap.

Second, we need to manage and regulate — yes, regulate — groundwater.  It’s a finite supply, and as long as there’s no limit on the number of straws in the cup and how much they can slurp, the water level will keep going down. Pumping limits would promote more efficient water use.

Third, we should stop letting antiquated water laws trump sound economics.  If farmers were readily able to sell or lease water to cities and conservationists, they would have incentive to invest in more efficient irrigation practices, switch to less thirsty crops, or fallow a portion of their fields so they could sell the conserved water to others.  A healthier water market could help cities meet long-term needs and even help rivers weather a drought.

This, in part, is the spirit behind the Colorado River System Conservation Program, which would pay for voluntary reductions in water use – whether by fallowing farm fields, installing more efficient irrigation systems, recycling industrial water, or other means – that benefit the basin as a whole.

Lastly, management of Colorado River Basin water is overseen by a long list of federal and state authorities.  While collaboration has improved greatly in recent years, it’s imperative to cooperate around groundwater monitoring and reporting in order to get a basin-wide view of what’s happening underground.

The findings of this study are a wake-up call, and it would be foolish beyond measure to push the snooze button.

[Disclaimer: The editors of Geophysical Research Letters asked me to serve as a reviewer of the Castle et al. manuscript, which I did.]

Sandra Postel is director of the Global Water Policy Project, Freshwater Fellow of the National Geographic Society, and author of several books and numerous articles on global water issues.  She is co-creator of Change the Course, the national freshwater conservation and restoration campaign being piloted in the Colorado River Basin.

Comments

  1. María Cristina Alonso
    Oviedo, Asturias, Spain, Europe
    September 17, 2:40 am

    Good morning, I would like to know if you are aware of three important facts regarding water depletion.
    One: Mass loss as a direct result which is what ‘Grace’ twin satellites can monitor from space because of the slight variations on gravity force measurements depending on distances and density distributions, can lead to an unbalance between forces pushing downwards, and upwards throughout the surface which is the object of these pulls. This results in earthquakes at certain points where the Earth crust is weaker, such as faults.
    Two: It is a very common error to learn things as we are told they are, thus resulting in assuming or not assuming that things are as we were told they are, and this makes me wonder what happens with water and its magnetic properties, and changes in its behaviour related to its temperature and salinity concentration distributions. Whereas we are told in Chemistry lessons that water is sort of, a substance with which to adjust reactions’ stoichiometry, and it has not magnetic impact, I, by myself, have thought on how salty water becomes sensitive to magnetic fields; paramagnetic water, or more accurately paramagnetic watery solutions.
    Three: Osmosis. It is a property which causes a gradient on flow’s circulation from lower to higher concentrations in solutions in order to balance salinities.
    I’ve been thinking about these matters because of the Bardarbunga, Iceland seismic crisis, which is currently active and it is not the only seismic crisis taking place right now in the world, this world, the only one we all have.
    If you are interested in reading more about these topics from my point of view, you are all invited to visit my blog.
    http://learnwareenglish.wordpress.com/
    Make yourself at home!

  2. Patricia
    New York City
    September 12, 1:19 am

    I just don’t comprehend why humans have to destroy everything that is given to us compassion humbleness nobility kindness respect for earth life animals unconditional love for anything natural and God given has gone out the door it is very unfortunate and sad I feel all this things have the hand of the powers that.be even the weather iam just saying I don’t know 100 percent but money greed and power seem to be the norm everything is put in the back burner all is including human lives. What can I say except we should pray and try to take care first of each other than our animals earth and anything that is beautiful and gifted and god given to us if we can get pass the greed power control and money we need to gave unconditional. Love.for every

  3. Mike
    Florida
    August 30, 8:20 am

    Just like DJ said, we need to take back this country before we can fix it. Bandaids aren’t enough, and we won’t do better so long as corporations control everything, including our government.
    Take America back!

  4. William Allman
    Gallup, NM
    August 28, 7:23 pm

    In addition to everything else, the city of Los Angeles has been pumping water for decades from the aquifer on which it sits, resulting in a 2-inch-per-decade drop and placing greater stress on the San Andreas fault. Since I read that in an article more than 30 years ago, and given the increase in population and concomitant agricultural expansion since then, I think it would be safe to assume that rate of sinking has increased, hastening the day when scientists say it is certain that whole area will slide into the ocean.

  5. Sheila Jones
    Phoenix, AZ
    August 28, 6:57 pm

    I love all the studies they have been doing on the thirsty Juniper tree, they are taking over some parts of AZ. Every little bit helps!!

  6. DJ
    Indiana
    August 28, 1:45 pm

    As long as we allow corporations to run this country we are not going to see any real solutions only bandaids. We the people are just finding out about this crisis because the corporations own the news companies and decide what we see on our TVs. We as a people are going to have to take our government back first of all then we are going to have to make changes that will effect us all last like water rationing, no more watering lawns, new farming practices, no more swimming pools, reclamation of grey water and yes desalantion plants in major a major way. Redirecting water from other parts of the country is only a bandaid and won’t solve the real issues. Think about Mexico’s problem in they receive no water from the Colorado river because we use it all. Our forefathers are turning in their graves at what this country has become. The world is popping out babies when they dont have jobs let alone thinking about what the quality of life these children will have. As a human race we are going to have to make some really hard decisions if we want to see the next century.

  7. mary karen
    tennessee
    August 28, 9:35 am

    We are blessed with some of the world’s best tasting water and plenty of rainfall here in west tennessee. Because of that, folks around here are pretty much oblivious to the water issues out west. But things could change as every year I see more and more farmers punching wells to irrigate their fields in an effort to raise profits. They don’t look at the long term problems that are being created – not just depleti I n of water table..
    But what scares me the most is that water and mineral rights all over the WORLD are being purchased by – you guessed it – the oil and gas companies or their board members. The first thing Bush did after leaving office was water rights to one of the largest aquifers in world. When it comes to regulating – and it will as I firmly believe that these gluttonous companies are waiting in the wings for water prices to get sky high – they will be ready to jump in. And you thought gas was high??? Honey you ain’t seen jack!
    We can self regulate or sit back and wait for the “1%” to do it.

  8. Joe Kirby
    Carlsbad NM
    August 27, 6:47 pm

    Is anyone in the oil and gas industry recycling the water used in the drilling and fracking process ? This would improve their image with the public fir sure. Also curious as to drip farming. Is this something that could replace irrigation in the future to conserve agricultures use if water. I would like to see more national awareness of this global dilemma. So many american people are unaware of the facts. I’m shocked when I meet educated people who are clueless as to the worlds shortage of this most precious commodity . I believe educating our youth may be as important as all conservation efforts we put in place.

  9. Rebecca Laureano Thornburgh
    United States
    August 27, 6:44 pm

    I am so in shock that so people in this country just turned their..at 62 I look at my grandchildren sadly hoping someone will come up with solution…so they may have a future on this planet.I have tried over the years to educate people about rationing water..turn off lights etc. I still have a brick in each toilet..bless each and every one of for trying to help.

  10. Mom
    Utah
    August 27, 6:35 pm

    Nothing will benefit human health and increase chances for survival of life on Earth as the evolution to a vegetarian diet. -Albert Einstein
    A local vegetarian diet :)

  11. Jon
    Kingman AZ
    August 26, 3:17 pm

    I wrote to the California Governor about running a series of large PVC pipe lines, from the western edge of lake Superior about 2,000 miles to upper Ca. with feeds going south to other drought stricken states when in need.. Lake Superior has enough water to flood both north and south America two feet deep. much of the water from the lake runs south and finds its way to the gulf of Mexico into salt water

    • Sandra Postel
      August 26, 4:01 pm

      The Great Lakes states and Canadian provinces signed a compact a few years back banning large diversions of water from the Great Lakes. Check out the Great Lakes Compact.

  12. C.Kafura
    United States
    August 24, 12:00 am

    Way too much turf grass in suburban and urban areas. Uses a lot of high quality water. Needs to be cut with a mower using fossil fuels. Treated with pesticides and fertilizers that poison the environment. Poor ecological habitat value. Labor intensive. Also, boring in my opinion.

    Water is being transported from the west slope through tunnels under the continental divide to the front range in CO to water lawns. Water is being transported hundreds of miles in canals to water lawns in metropolitan Phoenix.

    Alternative: Gray water and rain water harvesting to grow native food, shade, and habitat producing plants.

  13. Paul Suliin
    Colorado
    August 13, 3:30 pm

    I noticed a couple of people mentioning gray water. Unfortunately that’s not as simple a solution as people think it is. Yes, gray water can be re-routed easily to water the same household’s lawn or garden, but remember that large-scale agriculture uses 80% of the water in the basin. That means a whole separate piping system to route gray water from households to the farms where the vast majority of the water is used. Household water conservation can have only a small effect on the current situation.

  14. Paul Suliin
    Colorado
    August 13, 3:02 pm

    I noticed that over 10 years (2004-2013) the groundwater in the Colorado River basin was depleted by an amount sufficient to meet the needs of the entire US for 8 years. My question is, how is that possible? Did those 7 states really use in 10 years as much water as the entire US uses in 8 years? If not then where did the water go?

    • Sandra Postel
      August 13, 3:33 pm

      Most of that groundwater depletion in the Colorado Basin is attributable to water used for crop production, not home use. In order to provide a sense of how much water it is (since millions of acre-feet is not something most can grasp), I made the comparison to the number of years of home water use for the US population that volume could supply, and arrived at 8 years.

  15. Dan
    San Francisco
    August 7, 3:21 pm

    Do the aquifers have any other function besides supplying humans? Are there any species or ecosystems that rely on them? Or do they mostly just exist as pockets of water?

    • Sandra Postel
      August 13, 3:38 pm

      Many aquifers have hydrological connections to rivers and provide critical base flows, especially during the drier summer months. When those aquifers are overpumped and water tables are drawn down, the base flows can diminish, drying up a river and greatly harming fish and aquatic life.

  16. David Morales
    Mexicali, B.C Mexico
    August 7, 1:06 pm

    Aqui en el otro lado de la frontera, las personas desperdician agua como si nunca se fuese acabar, y eso debe estar en conciencia, ya que Baja California depende mucho de las aguas del Rio Colorado..

  17. Scott haralson
    Grove Okla.
    August 3, 7:50 pm

    Living in Okla. I watch the Gas & Oil Pigs, use our water to make obscene profits,then replace it by pumping back poison water into the ground, all the time creating many,many 3.5 earth quakes that we never experienced prior to franking.

  18. Jeanne
    Shingletown, CA
    August 3, 2:30 pm

    If California lawmakers would use their brains, they would allow us to use our gray water. Just think about how much water is wasted in our kitchen sinks, dishwashers, and bathtubs. Yet it is illegal to use it without going through so much red tape. All that water could be used to grow crops, water lawns and help keep the farmers in business. And therefore help keep our price of groceries from skyrocketing. and keep California green.

  19. Gene Holmes
    Atlanta GA
    August 1, 12:33 pm

    Your list of cities relying on Colorado River Basin water
    should include Denver, which gets it through a tunnel under the Continental Divide. One proposed solution is a 600 mile pipeline to Denver from the Missouri River.

    • Sandra Postel
      August 1, 1:36 pm

      Yes, thanks, it was by no means an exhaustive list: Denver, Albuquerque, etc… Denver gets about half its supply from the Colorado River.

  20. Tom Sweetnam
    Colorado remote
    August 1, 10:20 am

    The world’s population will be 10 billion by 2040. What will fresh water demand look like then? In his seminal portent, “The Coming Anarchy”, Atlantic Monthly editor Robert Kaplan illustrates that many of the “brush wars” raging on planet Earth today, especially in Africa, are all about water and grazing land for cattle…driven by overpopulation.

    Overpopulation was the root cause of land degradation in Northern Mexico (by the 1930′s), and to this day is one of the major causes of massive illegal immigration on our southern border, again driven by overpopulation.

    I think the best primer on water history, water usage, and water politics in the Southwestern US, is Marc Reisner’s ‘Cadillac Desert’. First published in 1993, it’s still as relevant today as it was 21 years ago. PBS did an excellent documentary based on Reisner’s book.

  21. GE
    Montana
    August 1, 10:10 am

    I want to know where is all this water going once it’s been used? The water isn’t disappearing. Also, where is the tech that could turn salt water into fresh water? It’s 2014!!!

  22. Bob Daniels
    Saudi Arabia
    August 1, 4:22 am

    Is fracking an issue in AZ, NV, UT, CA? Too many people, not enough water.

    • Sandra Postel
      August 1, 10:36 am

      Of the seven Colorado Basin states, fracking is biggest in Colorado and California, though CA’s fracking would not involve much if any Colorado River water.

  23. Kwang Yi
    Indiana
    July 31, 11:55 pm

    It’s an informative article, and I feel younger people should be made aware of this water shortage problems and the practice of conservation should be rigorously and systematically taught in school. The people in the US tend to take everything as granted. I’m living in a place where I’m being sued by HOA for implementing rain water collection system, because some people in this neighborhood believes 2 50-gallon water tank is too much of an eye-sore.

  24. nuala
    california
    July 31, 8:36 pm

    If it were not for farmers who grow all our fruits and vegetables and raise beef and sheep, the USA people would be hungry and it would be a third world country with its inhabitants starving.
    Is this what we want .Why do city developers keep giving out building permits which keep increasing the populations in cities such as Phoenix and Las Vegas. Can you imagine one large apt. complex would use in a week or a year.Why not go build in Oregon or Washington where there is a surplices of water,
    My way of thinking

  25. Lorien Elsey
    Las Vegas NV
    July 31, 3:23 pm

    I am HORRIFIED to see no mention of FRACKING as a CAUSE of the current water situation of the Colorado River. :( hello?? Anybody in there??

  26. Horrified
    New Jersey
    July 31, 2:11 pm

    Similar depletion is occurring in Oklahoma, yet use of limited water has been approved by the state for fracking. All of this will come crashing down, with the poorest paying the greatest penalty.

  27. LaNell
    Denver, CO
    July 31, 11:51 am

    Not one word about the enormous amounts of water used by the animal agriculture business or fracking. These two industries alone are more devastating to our water supply than any other. If we want to solve this problem, we have to be honest with ourselves.