National Geographic News
Dust bowl drought victims (migratory farm workers) at ramshackle building in Calif.

The Dust Bowl drought in the 1930s forced many farmers off their land. This farm family makes do in a ramshackle cabin north of Shafter, California.

Photograph by Dorothea Lange, Resettlement Administration/Time Life Pictures/Getty

Lisa M. Krieger

for National Geographic

Published February 13, 2014

A millennium ago—just yesterday, in geologic time—Native Americans waited all winter for rains that never came. They waited the next winter and the next. Then the marshes of their sacred San Francisco Bay turned from cattails to salt grass. Fishing declined and the Native Americans could no longer rely on the bounty of the bay. Finally, they left, hungry and thirsty, in search of water.

Now, as modern Californians hope for fierce storms to break a dangerous dry spell, the questions arise: Is the current drought just an aberration? Or might it signal the beginning of a more fearsome era, with echoes of the ancient drought that uprooted Native Americans? Is it a megadrought?

Most scientists sidestep a yes or no answer. But they agree that the past century has been unusually moist—and warn that California is now vulnerable to a drought that is measured not in years, but decades. Perhaps even centuries.

Aerial view of reservoir dried out during drought.
Photograph by Loomis Dean, Time Life/Getty
An empty reservoir shows the effects of drought in 1948.

On a trip to California's Central Valley on Friday, U.S. President Barack Obama is expected to link the drought to climate change and to announce federal aid aimed at "climate resilience."

But ancient clues in the landscape show this is not the first time the American West has been severely parched. It's unlikely to be the last. And the recent spate of dry years is nothing next to the ancient "megadroughts" that have occurred multiple times in human history. "What research shows is a roughly 50- to 90-year cycle of wet and dry periods over the last few thousand years, with some droughts lasting over a decade. But between 900 and 1400 A.D., during the 'Medieval Warm Period,' there were a couple of droughts that were over a century long," said B. Lynn Ingram, professor of Earth and planetary science and geography at the University of California, Berkeley, and co-author of the book The West Without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us About Tomorrow.

"The 20th century was a relatively wet time, and a time when all of our modern societies were built," she said. "We've had centuries where it was far drier. We're not prepared."

This winter is on track to be California's driest since it became a state in 1850, with reservoirs at record-low levels, farmers fallowing fields, and fire danger high. Although one recent storm offered a respite from months of sunshine, California needs four more similarly sized storms to catch up to the season's average precipitation, according to meteorologist Jan Null of Golden Gate Weather Services. And there's not much winter left.

Aerial photo of the Owens River in Calif.
Photograph by Jodi Cobb, National Geographic
The Owens River (mid-1970’s) in southeastern California nourishes little but its own banks.

Whether or not more rain comes this winter, the culmination of three years of below-average precipitation means that the state is entering its traditionally dry period from May to October with a dire water shortfall.

Weeks of dry skies conjure up uneasy memories of the drought of 1976-77, when Californians added bricks to toilet bowls and captured shower water in buckets. Or, more ominously, the Great Plains' devastating Dust Bowl drought of the 1930s, when the world's greatest grasslands blew away, soil blackened the sky, and lungs were packed with dirt and sand. Farmers fed thistles and cactuses to cattle so they wouldn't starve, and many abandoned their homes in search of rain and relief. The region lost a quarter of its population.

But the prehistoric record, re-created by paleoclimatologists, is even more alarming—and could explain why Native Americans abandoned their settlements and began wandering. Archeological records show that Native American populations expanded in wet years, creating flourishing civilizations. Then, during periods of abnormally low precipitation, settlements collapsed.

Clues From Ancient Trees

Like investigators at a crime scene, scientists are piecing together seemingly random evidence about ancient climates, deciphering clues about prehistoric droughts in sediments, tree rings, species distribution, and other natural evidence—a science known as dendrochronology.

The varying widths of tree rings, for instance, reveal that several pernicious dry spells gripped the West in the late 1500s. In a landmark study conducted in the 1940s, Edward Schulman reconstructed 600 years of Colorado River flow using ring records from long-lived Douglas firs, and found several sustained periods of low flow. It was so dry in 1580 that the giant sequoias in the Sierra Nevada essentially failed to grow at all; all the cores show either extremely thin or absent tree rings.

Photo of cracked earth due to drought in Jackson, Calif.
Photograph by Walter Zeboski, AP
The Pardee Reservoir near Jackson, California, supplies San Francisco with water. The reservoir was 103 feet below normal due to drought in 1977.

Another tree study, lead by University of Arkansas dendrochronologist David Stahle and Edward Cook of Columbia University, used more than 1,400 climate-sensitive tree-ring chronologies from multiple species across North America to reconstruct what's called "the Great Pueblo Drought," which occurred from 1276 to 1297 and may have contributed to the Anasazi tribe's abandonment of their magnificent cliff-dwellings in the northern Colorado Plateau.

Other megadrought evidence can be found in forests at the bottoms of lakes and streams, using tree-ring analysis and radiocarbon dating. Graham Kent, director of the Nevada Seismological Laboratory, found a forest in the Sierra Mountains dating back to the medieval era. A drought from 850 to 1150 drained the alpine Fallen Leaf Lake, leaving it barren enough for tall trees to grow, he concluded. Then the water returned, and the trees were preserved. An 800-year-old pine branch, recently salvaged from the lake, still smells pungently of sap.

Ancestral forests can also be found in recently exposed shorelines of eastern Sierra lakes and creeks. Scott Stine of California State University in East Bay tramped across an old lakebed and found dozens of ancient cottonwoods and Jeffrey pines rooted in place. Dating revealed that they grew when two severe and long-lasting droughts—from 900 to 1100, and 1200 to 1350—lowered the water level in the lake, then died when a return to a wetter climate filled the lake and drowned them.

A helitanker douses a hot spot in the huge Zaca fire.
Photograph by Vincent Laforet, National Geographic
Drought increases the risk of wildfires. Here, a helitanker douses flames in the 2007 Zaca Fire near Santa Barbara, California.

"Water dropped to 60 or 70 percent of what today we consider normal precipitation," he said. "The trees could colonize newly exposed shorelines." Stine has also discovered submerged tree trunks along the shoreline of California's Mono Lake, suggesting that the water level was once tens of feet lower than it is now. Studies of the lake's sedimentary stone show that the water fell to a very low level between 960 and 1460. Research in other Sierra lakes reveal a similar scenario: long dry-wet-dry-wet intervals.

With the drought came adaptation. Frances Malamud-Roam, Ingram's co-author, took sediment core samples in San Francisco Bay that indicate that the bay grew saltier due to the lack of freshwater runoff from the mountains, the presumed result of decreased rain and snowfall. She found evidence that the plant life shifted from tules and cattails, which thrive in fresh or brackish water, to saline-loving salt grass and cord grass.

Frightening Implications

If this is the past, what is the future?

Some scientists think we are already in a megadrought. Bill Patzert, research scientist and oceanographer at NASA's Jet Propulsion Laboratory in Pasadena, believes the drought began in 2000. He has identified patterns in the temperature of the Pacific Ocean that alter the flow of the jet stream, creating a ridge of high pressure off California that sends warm air to Alaska and freezing cold to the eastern United States. This pattern can hold steady for years, he said. (Related: "Could California's Drought Last 200 Years?")

A dry canal is filled with weeds.
Photograph by David McNew, Getty
A dry canal is filled with weeds on February 6, 2014, near Bakersfield, California.

If true, the implications are frightening: More wildfires. Stress on sensitive ecosystems. Less water for agriculture, cities, and wildlife. Wells would go dry, lawns would turn brown, fields would go fallow. There would be an earlier spring, with snowpack that melts quickly. The federal government would likely need to step in with billions of dollars of emergency aid. (Related: "Behind California's January Wildfires: Dry Conditions, Stubborn Weather Pattern.")

And modern Californians, unlike earlier populations, are not so easily uprooted. More than 38 million people, from Silicon Valley to Hollywood, depend on access to water. We've built cities, highways, universities, industries, and vast acres of irrigated farmland.

This image provided by NOAA compares January 13, 2013 and January 13, 2014 snow cover in Northern California and Nevada.
Photograph by NOAA/AP
Snow cover in northern California and Nevada was drastically diminished in January 2014 compared with the year before, as seen in these images by the Suomi NPP satellite.

It is time to begin facing that future now, scientists say, by reducing and improving the efficiency of water use. Increased emission of greenhouse gases will create a global one-way trend toward higher temperatures—making a dry landscape even drier.

"Today, in our technologically sophisticated world, it is easy to believe we are immune to such an outcome. But we have not been seriously tested," wrote Sandra L. Postel, director of the Global Water Policy Project and a National Geographic Fellow, in the introduction to Ingram and Malamud-Roam's book. "We have so successfully masked aridity that we have become imbued with a false sense of security about our water future."

Srihari Yamanoor
Srihari Yamanoor

Sustainability is a MUST. We need to remove some land off agriculture. Developments that destroy ecology need to stop. Also remember how 40% of food produced gets thrown out. That has got to go. Good luck getting any of this done. 

Rick Terry
Rick Terry

Scary, aquaponics and hydroponics may be beneficial.

Mark Witt
Mark Witt

Never plant in a desert and never build on a flood plain...we always are allowed to make the same mistakes. Better to think ahead and not act foolishly but we in America have big government to bail everyone out and insurance .Why think ahead when we can buy our way out of the next calamity. When we suck rivers dry to have golf courses and green manicured lawns,swimming pools in the deserts something is just wrong with that...what ever happened to common sense? Wing and a prayer is eventually going to come's going to happen and in some cases already has. Some orchards have been bull dozed for the lack of water...

Tony Cooley
Tony Cooley

The major user of water is agriculture.  We all have benefited from the lower cost of food allowed by irrigated production in these areas.  The farmers have substantial investments in their infrastructure.  If the drought is likely to be modest in duration, it would be worthwhile to provide aid to help them bridge the economic cost to survive until more water is available.  However, if we have good information that a long-term drought is occurring that we cannot bridge by simple measures, money would be best spent in adapting to the new conditions and helping the losers change to a different source of income instead of propping up the existing system.  Of course the inevitable ambiguity and uncertainty of long-term weather forecasting, as well as the natural desire of those whose livelihoods depend on the current system to continue that system, will cause substantial ongoing public investments in the current system for a long time after it becomes likely that we truly are going into a long-term drought.

I am very impressed with our scientific ability to use dendrochronology, palynology, and other tools to map out the extent and intensity of variations in water availability over such a long period of the past and with such temporal precision.  Kudos to those who developed the dendrochronology method for accurate dating and yearly growth information.  This works because multiple trees growing at the same time show the same pattern of variation in annual ring thickness that reflects local growing condition variations.  A continuous time record of these variations greater than the age of any single tree is created by obtaining many logs of various ages.  Taking the records from these old logs, identifying the parts that match the ring variations of parts of other logs, and overlapping these records at their matched parts allows the assembly of the full chronology.  The actual year of an event hundreds, or in some cases thousands, of years in the past can be identified.  Other dating techniques have a precision limited to much larger time intervals or percentages of the age.  The duration and actual dates of past droughts or correlation of two events, like a drought and population migration, can now be matched with much greater precision using this method.  It allows much more powerful conclusions to be formed.

Prediction is harder than clearly defining a long record of the past, which is hard enough.  Future events are driven by the specifics of many conditions, which then feed into complex and interacting mechanisms and processes to make our weather.  This was also the case with past events.  Unfortunately, we don't have a direct correlation between our record of what happened and what specific but unknown conditions produced that result in the past. There is still an interpretational and modeling step required to estimate how the past conditions of the record were produced.  This limits our confidence in our ability to predict the future.  At least having reliable information of past experiences provides a better basis for estimating the future.

We should not lightly make major changes in the way we allocate resources and invest in infrastructure.  Neither should we ignore the warnings that science can give us about likely future changes.  As we better define the water future of the western states, we need to have the political debate about our priorities and adjust our incentives to implement those priorities so we can mitigate the impact of decreased water (if that is the prediction) on those who already live there and have invested in their homes, workplaces, and infrastructure.  I anticipate that agriculture will end being the primary loser because of the economic clout and numbers of the non-agricultural users relative to their use of water as individuals.  Reducing agricultural use frees up a lot of water relative to the other users.  Unfortunately, it will also be hard to keep a constituency for protecting our wildlife heritage in our water use allocations.  A case must be made for the essential importance of this to sustainability of our use of the west.  The "bugs and bunnies" are not just photogenic. We both obtain benefits and avoid major ecological disasters by preserving as much as we can.

I'll end by commenting that I am very pleased that we will have such good data from the past to use in forming our future responses, whatever they may be.

Roger Bird
Roger Bird

LENR (cold fusion) is on it's way and will provide sufficient concentrated energy for desalinization.  Within 5 and 10 years, some of your electricity will be powered by LENR.  I guarantee it.  By 2029, ALL of your electricity will be powered by LENR.  

In the meantime, the only salvation for California and Nevada should this drought continue will be some form of very expensive desalinization, or people just migrating, or dying.  People should not underestimate how devastating a mega-drought can be.  It may come on slowly, but that could be it's most dangerous aspect.

Even if desalinization for cities and farming were feasible, the wild areas will still become deserts.  Not a pretty prospect.

Dwayne LaGrou
Dwayne LaGrou

And if they think that they can just pump water from the Great Lakes out west, They are sadly mistaken. It has already been proven that if that were attempted it would result in a complete collapse of the Great Lakes environment that would destroy it! There has to be better ways to help. They could do like they do in the middle east by using green energy sources to power desalination plants.

James H.
James H.

@Roger Bird  "Within 5 and 10 years, some of your electricity will be powered by LENR.  I guarantee it."

That's a BIG claim there Roger :-)!

Mark Fogarty
Mark Fogarty

The Great Lakes Compact prevents any state not bordering the Great Lakes from diverting any water from them. Not even an option. The west would just drain them dry like they already have to their own water sources.

Bo Galvin
Bo Galvin

@James H. @Roger Bird 

I have to agree James. I believe we are 20-50 years from fusion reactors.

Roger, where did you obtain your data?


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