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A photo of water in the Delta-Mendota Canal.

The banks of the Delta-Mendota Canal (shown here on February 25, 2014, in Los Banos, California) were raised 45 years ago in response to subsidence.

PHOTOGRAPH BY JUSTIN SULLIVAN, GETTY

Julie Schmit

for National Geographic

Published March 25, 2014

Extensive groundwater pumping is causing a huge swath of central California to sink, in some spots at an alarming rate, the U.S. Geological Survey reports.

With California in the throes of a major drought and demand for groundwater rising, officials and landowners are racing to respond to the process known as subsidence. Some areas of the San Joaquin Valley, the backbone of California's vast agricultural industry, are subsiding at the fastest rates ever measured, said Michelle Sneed, a U.S. Geological Survey hydrologist and lead author of the recent report.

While the bulk of the sinking 1,200-square-mile (3,108-square-kilometer) area in central California is subsiding only about an inch (2.5 centimeters) a year, one 2-square-mile (5-square-kilometer) area Sneed studied is subsiding almost a foot (0.3 meters) annually. At that pace, "lots of infrastructure can't handle such rapid subsidence," Sneed said, including roads, water canals, and pipelines. The drought is likely to exacerbate the situation, as less rain drives more pumping.

Sinking Lands Raise Flood Risk

The worst subsidence has already increased the risk of flooding in the sparsely populated region, including to the low-lying town of Dos Palos, population 5,400, said Christopher White, manager of the Central California Irrigation District.

That's because portions of the area's flood control system have sunk, reducing their ability to contain floodwater. Local flood officials are crafting emergency plans for where to place sandbags when big rains return.

"We've got some serious issues," said Reggie Hill, manager of the Lower San Joaquin Levee District, which maintains part of the flood canal.

Other canals and dams that deliver water to irrigate the fields of hundreds of growers are also losing capacity as parts of them sink.

White oversees the local effort to respond to the subsidence. His irrigation district, which serves 1,900 growers, spent $5 million in recent years to raise canals and dams.

The federal Delta-Mendota Canal, which delivers water from northern California to growers and cities in the Central Valley, runs near the edge of the subsidence bowl and was the focus of the USGS study.

In 1969 the canal's banks were raised four feet (1.2 meters) along a 15-mile (24-kilometer) stretch in response to subsidence. More renovations—including the raising of several two-lane bridges over the canal—will be needed in 20 years if the sinking in the area doesn't slow, said Bob Martin, an engineer with the agency that oversees the canal.

Sneed said more research is needed to assess the impact of subsidence on cities around the Delta-Mendota Canal.

One permanent impact to the region may be lost groundwater storage. As groundwater levels drop, clay deposits move closer together and space for groundwater is lost. "You can never get the deposits to go back," Sneed said. Groundwater provides about one-third of the area’s total water supply, even more in drought years, officials said.

A photo of an irrigation channel delivering water to farm fields.
An irrigation channel delivers water to farm fields in the Sacramento-San Joaquin River Delta near Isleton, California.
PHOTOGRAPH BY ROBERT GALBRAITH, REUTERS/CORBIS

Surprising Find

The rapid subsidence was first noted several years ago when the U.S. Bureau of Reclamation did survey work as part of an $800-million restoration of the San Joaquin River.

The land had settled so much "we thought our data was wrong," said Rick Woodley, a bureau resource manager. That led to further study by the USGS. Because of the subsidence, some construction tied to the restoration has been delayed. Anything built "needs firm footing," Woodley said.

The California High-Speed Rail Authority, however, said subsidence will not have a significant impact on plans for a new high-speed rail through the area. The system will run from San Francisco to Los Angeles and can be engineered to deal with sinking land, said Frank Vacca, chief program manager.

Long-Standing Issue

Sinking land is not new to the San Joaquin Valley. In the four decades prior to 1970, portions of the valley sank 28 feet (8.5 meters), the USGS reported. Other states also suffer subsidence, and groundwater extraction is often the cause.

In the San Joaquin Valley, subsidence largely abated when growers began pumping from large federal and state water projects built in the 1950s and 1970s that are fed by Sierra Nevada snowpack.

But growers say they're now getting less of that water as the snowpack has diminished and more water goes to sustain critical habitat for endangered species. That combination has renewed growers' demand for groundwater, especially in drought years when surface water supplies dwindle, said Timothy Quinn, executive director of the Association of California Water Agencies.

Landowners near the heart of the subsidence bowl are totally reliant on groundwater to irrigate crops, including almonds and grapes. More tree crops have also been planted in the valley, and they will die if left dry in drought years.

Local officials are working with landowners to reduce the deep groundwater pumping that causes subsidence, and to secure future surface-water resources and recharge shallow groundwater reservoirs, the Central California Irrigation District's White said.

California's groundwater is largely managed locally, but the renewed subsidence may spur more state oversight, Quinn said. "The groundwater situation in California will be a crisis long after the drought."

22 comments
Norma Okun
Norma Okun

my comment is simply to say if it isn't water the problem than is a rust fungus on the coffee bean.

Kath O'lieen
Kath O'lieen

How long it takes for all the agencies and municipalities to get on the same page (if ever) is anyone's guess. 

It will likely take a several dramatic events to get the power companies and CalTrans to revise their business practices to factor in this issue. In the meantime, continued overbuilding, industrial AG and other "business-as-usual" will continue until the damage is so great that they will finally just give up completely. 

What that will mean for the the people living at that time, it doesn't look very good unless there is proactive planning that is already at least a decade behind. California is a truly unique place in that it covers all but but one type of climate [tundra] and can be on the forefront of pilot programs in new building materials and approaches to better husbanding of resources for a sustainable future.

Kath O'lieen
Kath O'lieen

How long it takes for all the agencies and municipalities to get on the same page (if ever) is anyone's guess. It will likely take a several dramatic events to get the power companies and CalTrans to revise their business practices to factor in this issue. In the meantime, continued overbuilding, industrial AG and other "business-as-usual" will continue until the damage is so great that they will finally just give up completely. What that will mean for the the people living at that time, it doesn't look very good unless there is proactive planning that is already at least a decade behind. California is a truly unique place in that it covers all but but one type of climate [tundra] and can be on the forefront of pilot programs in new building materials and approaches to better husbanding of resources for a sustainable future.

KENNETH LANE
KENNETH LANE

California with it's losse soil, arid climate and over population situation pretty much gets what it deserves.  And what about that lousey food?

Dwayne LaGrou
Dwayne LaGrou

They have the technology and the materials to make a large scale desalination action plant or plants to work. In the middle east they rely almost entirely on salt water removing plants for all of their fresh water needs. California is RIPE with possiblities. Use Wave Generators, Solar and Wind power to run the plants and they will have all the fresh water they want! It's a simple matter of finding the right people to make it happen, And, To make it happen CORRECTLY & NOW, before they are scrambling around trying to pick at it for years, Wasting money and time.

It can and must be done. There are enough millionaires and Billionaires out there that could get together and do it. Besides, What other options will work in the long term?!

Nancy Smith
Nancy Smith

we has met the enemy, and it is us folks!  when demand exceeds supply, all h.e.l.l will break loose, but for now we only feel a little of that heat. technology isn't the answer, it will be more of a socio-cultural modification.

Nancy Smith
Nancy Smith

we has met the enemy, and it is us folks!  when demand exceeds supply, all h.e.l.l will break loose, but for now we only feel a little of that heat. technology isn't the answer, it will be more of a socio-cultural modification.

John C.
John C.

So, why are they pumping millions of gallons of fresh water into San Francisco Bay to save the delta smelt?

Justin Smith
Justin Smith

All cities, manufacturing and power companies in California should switch to desalinated water and let the farmers and the rest have river and underground water. That would help out a lot.

Billy Corners
Billy Corners

i wonder if its possible to use salt water to recharge a deep ground aquifer.

Swiftright Right
Swiftright Right

@Dwayne LaGrou  Yeah but unfortunately the real world demands systems that work not crap from the cover of PopSci.


Have you been to the middle east? Im guessing not since you have not had to foot a middle eastern water bill. let me give some prospective.

The average cost of a cubic meter of water in the US is about 37 cents. That figure is what a consumer pays with NO subsidies.


The average cost of 1 cubic meter of water Kuwait is (as of 2008) $4.99 of which the government subsidizes $4.30 for a consumer cost of 60 cents per m3. These prices assume mass quantities of cheap oil. Solar and wind would probably double that cost, Wave power is a pipe dream, we are about as close to a working fusion plant as we are to industrial wave power.

Swiftright Right
Swiftright Right

@Nancy Smith  As I see it people are going to have to start ponying up cash OR start working like we use to. 


Californian's farmers use 45% of the states water to produce cheep and bountiful produce. simply put they need to drastically cut their water use. 


Virtually all ways to do that are either capital intense (hydroponics tented fields and drip irrigation) or work intense (terracotta pots, hand watering)  or simply cutting production. All of them result in a serious mark up in produce costs. 


At that point supply and demand kicks in, if you want a head of lettuce you grow it. Yes its work intense and yes you have to get your hands dirty but a 99 cent seed pack can produce $100-200 of greens. Producing it yourself also has the added benefit of not having to use gas or jet fuel to move a pound of picked peppers from Napa valley to NYC.

Aldo Leupold
Aldo Leupold

@John C. The smelt argument, the golf course and even the residential lawn argument is just a smoke screen to the real issue with California water, keep in mind that the single largest water user in Ca is agriculture, who made $44,000,000,000.00 last year alone growing luxury crops (grapes, almonds) in a desert. Meanwhile Google "Resnick water wars" and see how another set of crafty billionaires are manipulating our water resources to make billions off of a public resource.


And meanwhile, pay no attention to the man behind the curtain,, SMELT!! LOOK OVER THERE!!!

Swiftright Right
Swiftright Right

@Justin Smith  Not really, most of the major utilities are located by the coast and use sea water because its free. Manufacturing and home use are (literally) a drop in the bucket compared to farm use. 


Agricultural and irrigation uses 65% of every gallon of fresh water currently available. 


Manufacturing, industry and power use 5%

Andrew Booth
Andrew Booth

@Billy Corners No Billy. From what I understand the aquifer contains what's known as 'fossil water'. The aquifer took about ten thousand years to fill with water gradually filtering in through the substrate from rainfall in far and distant terrains. Over the last 200 years it's been very quickly pumped out and it will take thousands of years to refill naturally.

If you pump in salt water then you can only inject into very localised areas rather than across the whole aquifer. Secondly, the salt water can't be consumed by people or animals so it would be poisonous to all life. The aquifer water would also emerge from springs or as ground water and poison any land and watercourses it comes into contact with. The aquifer would then remain dangerous for many thousands of years and it would cause a disaster on the scale of Chernobyl.

The only answer is to stop pumping the fossil water.  

Andrew Booth
Andrew Booth

@Cynthia Carlson But how can it ever end? 

With a constantly increasing population and a continually increasing demand for water for drinking, lawns, golf courses, crop irrigation etc the whole system is going to slam into the buffers in the not too distant future.

Dwayne LaGrou
Dwayne LaGrou

It beats the heck out of me! I'm from Michigan and LOVE the fact that we have 4 distinct seasons that we can enjoy year long. To me, having sunshine and warm weather year round would be boring. Us folks in the upper mid west and north east have more diversity then we could imagine. From the most fresh water shore lines in the world to mountains and plains and caves to gaze at. I can't think of one reason to live there except Hollywood. And I think they have enough celebrities already!

Swiftright Right
Swiftright Right

@Andrew Booth @Cynthia Carlson  My guess it will end when global civilization crashes and the population  gets cut 60-90%. 


For as smart as we are suppose to be people en mass behave exactly like bacteria in a petri dish. The population grows and grows till it crashes.

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