Lake Powell, the Colorado River's second-largest reservoir, in April 2010 (Photo: Gretchen Weber)

There’s some good news for the 35 million people in the Western United States who rely on the Colorado River for their water, says a new study from the Oakland-based Pacific Institute.

No, the supply isn’t increasing.  And yes, the population is still growing.

But according to the paper, entitled Municipal Deliveries of Colorado River Basin Water, more efficient water use by water agencies across the West is making the supply/demand gap a lot less painful than it could be.

“Although population growth has increased very quickly, the amount of water delivered has not kept pace,” said study author Michael Cohen. “That shows that people have been getting much more efficient with their use of water.”

According to the report:

• Since 1990, the number of people who rely on water from the Colorado River basin has grown by 10 million. But during that time, per-capita water use has declined an average of one percent per year.
• Water agencies in Southern California delivered four percent less water from the Colorado in 2008 than they did in 1990, despite delivering water to almost 3.6 million more people.

Cohen said he was surprised and encouraged by the study results, and while he credited some of the efficiency to short-term policies (such as temporary drought restrictions) and new standards (like more efficient toilets and fixtures), he said that a lot of the change is likely due to changing attitudes.

“People are becoming much more aware of the value of water in the West, becoming sensitive that it is, in fact, a limited resource, and a resource that should be used wisely,” he said.

Not everyone in California is embracing efficiency, however.  Of the 100 water agencies studied, those with the three highest per-capita water deliveries are in California; the City of San Marino and two districts in Coachella Valley.

“They think it’s appropriate to have lawns in the middle of the desert even though they have to water them two or three times a day,” he said.  By comparison, he said, there are other, less affluent parts of Coachella Valley where water usage is about average for the state.

“Lots of agencies say [water usage] is driven by climate, but here’s a pretty stark example of cities or agencies with the exact same climate, but very different water use patterns,” Cohen observed.

Of course, what this study does not look at, is the 500-pound gorilla that is agricultural water use, which uses 70% of the water from the Colorado.  Municipal deliveries comprise just 15%, although it is the fastest growing segment of water use.

It seems that whatever efficiencies can be implemented now in any sector will only serve to ease what’s likely to become an even starker gap between supply and demand.  According to the Bureau of Reclamation, demand has recently outstripped supply along the Colorado, and a new federal study released earlier this month finds that the river’s flow could decrease 9% in the next 50 years due to impacts of climate change.  Meanwhile populations are expected to continue to grow rapidly in many regions dependent on the river.

“The question is, how are they going to balance supply and demand in the future,” said Cohen. “I think this report shows that at least part of that answer lies in more efficient use within the cities themselves.”

Lake Mead, the Colorado River's largest reservoir in May, 2010 (Photo: Gretchen Weber)

The Colorado River is a critical source of water for more than 30 million people throughout the western United States. California alone gets more than a trillion gallons of water each year from the Colorado. But over the years, recurring droughts and the growing demands of urban populations have stressed the river system, which the Bureau of Reclamation now characterizes as “over-allocated.”  In efforts to plan for the region’s future water needs, the agency, in collaboration with Western states, has undertaken a two-year study to look at what lies ahead for the river and the cities, farms, and families that rely on it.

On Monday, the agency released the first interim report of the “Colorado River Basin Water Supply & Demand Study,” which projects changes in the river’s flow under four different scenarios. A model that incorporates predicted impacts of climate change shows a nine percent reduction in the Colorado’s flow within 50 years.  The study also projects more frequent and more severe droughts throughout the system.

According to the report:

“Under the Downscaled GCM Projected scenario, the mean natural flow as measured at Lees Ferry over the next 50 years is projected to decrease by approximately 9 percent, along with a projected increase in both drought frequency and duration as compared to the observed historical streamflow record. Droughts lasting 5 or more years are projected to occur 40 percent of the time over the next 50 years.”

That likely means harder times for those who rely on a river that already has little water to spare.

In a statement Monday, the Environmental Defense Fund (EDF) applauded the study’s focus on potential climate change impacts, but urged the agency to find ways to address the supply/demand imbalance while still maintaining “healthy” river flows.

“The economic well-being of rural communities and major cities in the basin are inextricably linked to the environmental health of the Colorado River itself,” said EDF’s Rocky Mountain regional director, Dan Grossman. “And just as human health depends on healthy blood flow, the Colorado River’s health depends upon healthy water flows that are being compromised by current management practices and policies, as well as a warming climate.”

The next interim report is expected in the Fall of 2011, and a final report is due in July of 2012.  According to the Bureau of Reclamation’s website, the study will, “define current and future imbalances in water supply and demand in the Colorado River Basin and the adjacent areas of the Basin States that receive Colorado River water for approximately the next 50 years, and will develop and analyze adaptation and mitigation strategies to resolve those imbalances.”

Peter Osterkamp hopes his generation of farmers isn't the last in the Imperial Valley. (Photo: Krissy Clark)

Clichés about water in California can seem more abundant than the water itself these days.  But that doesn’t make the clichés any less true.

There’s that Mark Twain saw about how “whiskey is for drinkin’ and water is for fightin’,” and the line about how water flows uphill toward money.  And then there’s the time Twain fell into a California river and “came out all dusty.”

All those quips seemed fairly dead-on when I was down in the desert of southeastern California recently.  I was reporting for two radio stories on how Imperial Valley farmers are facing the double wallop of an eleven-year drought (and counting) in the Colorado River basin, and the expected effects of climate change.  Recent models suggest that Lake Mead — the giant reservoir that stores Colorado River water for Imperial farmers and much of the Southwest — has a 50% chance of drying up in the next 50 years.  Talk about dusty.  And because the Colorado is so over-allocated already, no water is left by the time the river reaches — make that attempts to reach — the Colorado delta in Mexico.  More dust.

That cliché about water flowing toward money actually cuts both ways in the Imperial Valley.  It once benefited farmers here.  As Marc Reisner reminds us in his seminal book, Cadillac Desert, the main reason this piece of desert can grow anything, let alone supply the U.S. up to 90% of its winter vegetables, is thanks to a handful of wealthy land owners and railroad magnates. In the early 1900s they helped secure priority rights to about a fifth of the Colorado River’s total flow, funded construction of irrigation canals through nearly 100 miles of desert, and later used their considerable political clout to help convince the federal government to improve those canals and build Hoover Dam. Though, to be fair, the canals are completely gravity fed.  So the water never technically flowed uphill to Imperial Valley.

But as populations continue to grow in California cities, and farmers’ political clout shrinks, water has started flowing away from Imperial Valley, up over the coastal range, to Los Angeles and San Diego.  Phoenix and Las Vegas are thirsty for some of it too. California cities are already paying farmers to fallow some of their fields and to make their operations more water-efficient.  In exchange, farmers have agreed to start transferring more than 300,000 acre-feet of water annually to cities, enough to serve about 500,000 households.

A dry irrigation channel alongside a fallowed field in the Imperial Valley.

Farmers still have rights to more than two million acre-feet, but if the drought continues and climate models are correct, they may be pressured to give up more.  John Pierre Menvielle, a retired farmer on the Imperial Irrigation District Board, says farmers can’t afford to transfer more water without doing real damage to the agricultural economy, though they may not have a choice.  “We do worry about the voting populace on the coast.  You’ve got 17 million votes over there.”  Then he squints his eyes and adds “that’s why we have lawyers,” lending credence to Twain’s water-is-for-fightin’ remark.

Doug Kenney, of the Western Water Policy Institute at the University of Colorado, says the tug-of-war over water between farmers and cities is more complicated than just who has the most money or political clout.  “It’s not just the agricultural community that wants to keep its water.  The urban community typically likes to be surrounded by an agricultural community, and its viewed as a valuable amenity.” But at some point, Kenney says, economics wins.  “If the cities need more water, and that water is currently in use by farms, and the cities are willing to pay 10, 20, and maybe 100 times more for that water than the farmer can, at some point that water has to move to the cities.”

But if climate in the Colorado River basin continues its arid trajectory, a massive water transfer away from farms to support more urban growth has risks. “If you’re a farmer and one year comes along and you only have half your normal water supply, well, you can probably get by,” says Kenney.   But cities are less flexible in a drought.  If “the city grows up on that water supply, and then you have a situation where one year there’s only half of that supply, it’s a little more problematic,” he says.

Whiskey may be for drinking, but contemplating the future of this corner of California in the face of dwindling water supplies, is pretty sobering.

View of Lake Mead on 9/9/10 (Original image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center. This version produced by Tom Yulsman of CEJournal)

Lake Mead is the largest reservoir in the country.  It’s located on the Colorado River, which provides water for about 27 million people in seven states, including millions of Californians.  In fact, California gets more than a trillion gallons of water from the Colorado River each year, directly from Lake Mead via the Colorado River Aqueduct which snakes across the desert.  Eighteen million people in Southern California are dependent on the Colorado for 40% of their water.  And for some agricultural operations, that percentage is more like 100.  Needless to say, it’s a critical source of water.

The thing is, after 11 years of dry conditions in the region, Lake Mead dropped to its lowest level ever in October.  And so far, it’s stayed there.  Since Hoover Dam was completed in the 1937 the water level has never been so low.  As of today, it’s at 38% of capacity.  And it’s not just Lake Mead that’s low.  The whole Colorado River storage system is at just 55% of capacity, so forget just filling it up with water from upstream.  Of course, winter’s on it’s way, and with that, precipitation, so the lake shouldn’t stay quite so low for long.  And, thanks to a wet year, Northern California’s reservoirs are doing well.

But when you think about this water shortage in terms of population trends and the changing climate, the future for water in the Southwest looks grim.  Population areas supplied by the Colorado River are some of the fastest growing in the country. So demand is going up.  At the same time, scientists and water managers say the supply will go down.  The region is expected to get warmer and drier in the coming decades, which means less precipitation, and more specifically, less snow.  Which means that of the precipitation that does come, more will come as rain, which is harder to capture and store for use throughout the dry summer months.

In fact, studies show that the river’s flow is likely to decrease 10-15% in coming decades due to climate change, according to the Bureau of Reclamation’s Terry Fulp, and, he said, the demand is already outpacing the supply.

“The supply and demand curves have crossed,” he told me last May.

The question of just how long the Colorado River can continue meet the needs of seven states with growing populations, depends on how quickly those supply and demand curves are diverging.   Scientists have given varying estimates of when Lake Mead will go dry, but recent studies estimate a 50-50 chance that it could happen before 2057.  (Earlier studies had estimated it as soon as 2021.)   The state’s population is expected to increase by half, to nearly 60 million, by 2050.

So, Californians, what happens then?  And what should we be doing now to prepare?  It might be worth thinking about.  In 2060, taking shorter showers and turning off the water when you brush your teeth might not be enough.

With cores from trees like this one, scientists have been able to reconstruct more than 1,000 years of climate history in this region. (Photo: Gretchen Weber)

Abbie Tingstad is a paleoclimatologist whose doctoral work at UCLA involved reconstructing climate in the Upper Colorado River Basin, using tree rings and lake sediments.

By Abbie Tingstad

Unlike biology, chemistry, or most mainstream sciences, it’s hard to envision what someone who studies paleoclimatology actually does. I run into a lot of blank stares at dinner parties. So I’ve started describing the field as “climate forensics.”

Paleoclimatology and forensics of the Law & Order or Bones variety share the basic goal of reconstructing something that has happened in the past. In the latter, of course, the sequence of events that led to a crime is put together. In the former, researchers identify past variations in climate.  These sciences also have quite a lot in common when it comes to the basic methodology:

1. Collection of evidence
I’ll use the example of tree rings, something I have direct experience working with from my research in northeastern Utah. Based on river gauge data, this area of the Colorado River Basin originates 10-15% of Upper Basin water, which is why my colleagues and I were interested in understanding the incidence of past droughts here.

In this case, my climate “fingerprints” were moisture-sensitive Piñon pines. We searched for sites that appeared to have very old living trees — identifiable by trunk size, the open appearance of the branches, and the presence of dead limbs — and lots of dead trees. We used a manual coring device to take pencil-sized samples from both living and dead trees.

2. Lab work
Back at UCLA, I mounted the delicate samples onto wooden holders with an adhesive. Then my assistants and I sanded each sample using progressively finer sandpaper, until individual cells within annual rings were visible under a light microscope.

I counted the annual rings on each of the live samples back in time, starting with the ring closest to the bark. I noted recurring patterns of narrow rings, which are generally associated with climate events unfavorable for tree growth (for example, during the Dust Bowl drought). These patterns allowed me to identify when the dead trees lived. As I had hoped, some of the dead trees were older than any of the living trees, allowing a longer reconstruction.

After dating the samples, I measured the widths of the annual rings using a microscope attached to a computer. I then used statistical software to check the accuracy of my dating and to generate one time sequence per site, based on the ring widths of all the individual trees.

3. Reconstruction of events
In a crime lab, analysts will compare fingerprints, residue samples, or other forms of evidence with a database to place the evidence into context. Paleoclimatologists do the same, except we use instrumental climate information. In the Uinta Mountains research, I found that the tree rings correlated well with measures of moisture such as streamflow and snowpack over the 20^th century time period for which instrumental data are available. Using a statistical technique called linear regression, I developed a mathematical expression to estimate these climate variables based on tree ring widths. Applying these models to the entire data sets, I developed reconstructions for Uinta Mountains streamflow and snowpack going back several centuries.

My colleagues and I used these estimates of past hydrology to analyze drought frequency, length, and severity. This information extends knowledge of baseline conditions for water management beyond the 20th century.

4. Comparison with other lines of evidence
Even if a paleoclimate record may appear to be a “smoking gun,” researchers validate their work by developing climate reconstructions for a particular area based on different types of data and/or by comparing their work with that of others. As in criminal investigations, the strongest case is made when independent forms of evidence all point to the same conclusion.

At the end of a paleoclimate investigation, researchers are able to present strong evidence for things like long droughts in the Western U.S. during Medieval times, or shifts in the way El Niño behaves, or that late-20^th century temperatures are high in the context of relatively recent Earth history. However, paleoclimatology is an imperfect science. Tree rings, lake and ocean sediments, corals, glaciers, and other archives imprinted by past climates cannot compete with modern instruments. But like many good crime scene reconstructions, a few distorted or missing bits don’t make the big picture wrong.

Paleoclimatologist Abbie Tingstad holds samples of tree cores at the base of an ancient pinon pine at her research site in northeastern Utah. (Photo: Gretchen Weber)

Historic water marker on the shores of Lake Powell, April 2010 (Photo: Gretchen Weber)

People have been talking about “peak oil” for decades now, debating when oil production will peak and then start to decline as remaining resources become scarcer and harder to access.   Less attention has been given to the idea of “peak water,” which is the subject of a new analysis by the Oakland-based Pacific Institute.  The concepts of peak oil and peak water aren’t entirely analogous for a number of reasons, not the least of which is the fact that, overall, water is a renewable resource.  But there are limits to what water is renewable, and how fast supplies recharge.  While the world is not going to run out of water, the report authors argue, in parts of the world including the southwestern US, we’re likely long past the point of peak water.  That matters a lot, said study co-author Meena Palaniappan, because unlike oil, which is shipped across the world, water is still a local and regional issue.

“We’re not going to run out of water,” said Palaniappan, “but we’re going to see a change.  We’re at the end of cheap, easy access to water.  We’re going to have to go further, pay more, and expect less in terms of fresh water.”

The report divides peak water into three types: peak renewable water, the total annual supply of water from sources such as rainfall, rivers, and groundwater sources that are refilled relatively quickly; peak non-renewable water, which includes groundwater aquifers that either do not refill or do so extremely slowly; and peak ecological water, past which, the value of ecological services provided by water is greater than the value it provides in direct human services.  Or simply, it’s the point where taking water causes more ecological damage than it’s worth.

“The goal is to find the sweet spot, where we can maximize the human value water provides as well as the ecological value,” said Palaniappan.

In the western US, we are definitely past peak ecological water, said Palaniappan.  As evidence of this, she cited the Central Valley aquifer, which is being pumped down far faster than it can recharge and the Colorado River, which supplies Southern California with much of its water, and no longer reaches the ocean most years because every drop of it is appropriated for human use.

Last week, I was in Salt Lake City to talk with Terry Fulp, the Bureau of Reclamation‘s Deputy Regional Director of the Lower Colorado Region.  He said that after 10 years of drought on the Colorado, each of the seven states that draw from it are still getting their allotted water supply, and the reservoirs are about half full.  The Colorado River system, which supplies water to more than 30 million people, has a huge storage capacity, equal to four times the river’s annual flow, Fulp said. But increasing demand due to the drought and to population growth have the Bureau looking ahead at the challenges the system may be facing in the not-too-distant future.

“The supply and demand curves basically have crossed,” said Fulp.  “If you look over the last 100 years, the water supply has been above the demand, but demand has been growing, and essentially, today they have met.  We’re operating on a tight margin, a very tight margin, so the question is about projecting what we think the future will look like twenty years out.”

Like Palaniappan, Fulp says that conservation is critical and may become increasingly so in the near future. But even so, he said he doubts the demand for Colorado River water is going to decrease. The supply may, however.  Long droughts are common in the paleorecord, and water managers are planning for an additional 10-15% reduction in flow due to the effects of climate change.   This matters a great deal in a system where just about every drop is spoken for.  Fulp says that developing methods for accessing new water supplies, such as groundwater and desalinization plants, needs to be central to a long-term water management strategy for the region.

Exposed turbine intakes and the "bathtub ring" at Lake Mead. Photo: Craig Miller

You can see a slide show of the retreating waters at Lake Mead and Hoover Dam and listen to my radio feature from The California Report. Also, The American Experience will rerun its documentary on Hoover Dam, Monday night on most PBS stations.

The Las Vegas Sun has a digital clock on its website, counting down to a theoretical doomsday when the city’s principal source of water would go dry. Wagering on that question may not have found its way into the sports books on the Strip–but it did become a lively pastime among engineers and hydrologists, when a report emerged from San Diego’s Scripps Institution, with a dire forecast. The paper, by climate physicist Tim Barnett, put the odds at 50-50 that Lake Mead, the giant reservoir behind Hoover Dam, would reach “dead pool” by 2017. That’s the point at which the dam shuts down and neither hydroelectric power nor water emerges from it.

The Barnett study “definitely raised eyebrows throughout the basin,” admits Terry Fulp, deputy director of the U.S. Bureau of Reclamation’s Lower Colorado Region, which operates Hoover Dam and Lake Mead. As it turns out, Barnett was a bit pessimistic. Subsequent work by him and others revealed that he overestimated the evaporation rate at Lake Mead, and omitted inflows below a certain point on the river.

The bottom line, according to Balaji Rajagopalan at the University of Colorado: Doomsday is not quite that near at hand. But that doesn’t mean it’s not on the horizon. “After 2027, the demand increase outpaces the supply decrease,” Rajagopalan told me in a recent interview. “And that’s why much of the risk explodes from 2027 to 2057.”

All of these studies are couched in probabilities, much in the same way that the Corps of Engineers talks about a “100-year” flood. Rajagopalan says: “Even in our study, we have a 50% risk [of dead pool], but that occurs in 2057. And that makes a big difference in terms of water managers, what they can do.”

One of those managers is Pat Mulroy, who directs the Southern Nevada Water Authority. Her constituents rely on Lake Mead for 90% of their water, so she says she’s not inclined to wait around for a consensus. “I mean, during the entire period of the ‘90s when we were bickering with our friends in the lower basin over surpluses, there was zero probability that the drought that we’re currently in was going to happen,” Mulroy told me.  “I’ve lost confidence in probabilities.”

The Bureau’s Fulp says the Colorado system leans heavily on the huge water storage capacity of Lake Mead and its sister reservoir upstream, Lake Powell. “We’ve known for decades that this system is highly variable and that’s why so much storage was built.” When filled to capacity (which it was, more or less, 10 years ago), Lake Mead alone can hold enough to put an area the size of Pennsylvania under a foot of water. But a 10-year drought has left Mead at just over 40% of capacity (so think of flooding something more the size of Costa Rica). Just as current evidence and climate models both point toward lessening flows on the Colorado, many parts of the southwest still see relatively high population growth.

Scientists continue to run their statistical models aimed at handicapping the Colorado’s demise as a dependable bringer of water. But as Fulp sums it up, “It’s really a debate about when. It’s not really ‘if.”

I regret an error of my own that appeared in the radio feature. I misstated the number of people in southern Nevada who are dependent on water from the Colorado. The correct number is about two million.

Photo: National Park Service

The Colorado River supplies water to approximately 27  million people in seven states and irrigates more than three million acres of farmland. In Southern California alone, it supplies 18 million Metropolitan Water District customers with 40 percent of their water.

So last year, when a study out of Scripps Institution of Oceanography reported that there’s a 50 percent chance that the Colorado River’s largest reservoir (and the largest reservoir in the United States), Lake Mead, will be dry by 2021, the news generated a lot of buzz.

But a new study out from the University of Colorado Boulder finds that despite a 10-year drought in the Colorado River system, the odds of draining the river’s delivery system before 2026 are pretty slim — below 10% in any given year.  Researchers say this is primarily due to the massive reservoir storage capacity along the Colorado — more than 60 million acre feet, which includes Lake Mead.  The reservoir system of the Colorado is currently at 59 percent of capacity, according to the study.

But the scientists predict that by mid-century, the Colorado could become less reliable unless water-management strategies change.

The researchers found that if climate change causes a 10 percent reduction in the Colorado River’s average stream flow as some recent studies predict ([PDF]), the chances of fully depleting the system’s reservoirs will exceed 25 percent by 2057.  If there is a 20 percent reduction in stream flow, the chances of deleption rise to 50 percent.

“On average, drying caused by climate change would increase the risk of fully depleting reservoir storage by nearly ten times more than the risk we expect from population pressures alone,” said lead study author Balaji Rajagopalan in a press release about the study.

The authors of the study conclude that the magnitude of the risk will depend not just on the amount of drying the region experiences, but also the types of water management and conservation strategies that are implemented in the near future.

For the last decade, California’s annual use of Colorado River water has varied from 4.5 to 5.2 million acre feet.

Photo: Adrian Fogg