Smaller Colorado River projected for coming decades, study says

Dec 23, 2012

(Phys.org)—Some 40 million people depend on the Colorado River Basin for water but warmer weather from rising greenhouse gas levels and a growing population may signal water shortages ahead. In a new study in Nature Climate Change, climate modelers at Columbia University's Lamont-Doherty Earth Observatory predict a 10 percent drop in the Colorado River's flow in the next few decades, enough to disrupt longtime water-sharing agreements between farms and cities across the American Southwest, from Denver to Los Angeles to Tucson, and through California's Imperial Valley.

"It may not sound like a phenomenally large amount except the and the river is already over-allocated," said Richard Seager, a at Columbia University's Lamont-Doherty Earth Observatory and lead author of the new study.

The study expands on findings published in 2007 in the journal Science that the American Southwest is becoming more arid as temperatures rise and shift from human-caused . It also comes on the heels of a major study of the by the U.S. Department of Interior that projected longer and more severe droughts by 2060, and a 9 percent decline in the Colorado's flows.

"The projections are spot on," said Bradley Udall, an expert on hydrology and policy of the American West, at the University of Colorado, Boulder. "Everyone wondered what the next generation of models would say. Now we have a study that suggests we better take seriously the drying projections ahead."

The present study narrows in on three key regions for —the Colorado River headwaters, the greater California-Nevada region and Texas, which gets nearly all of its water from within state borders. The study makes use of the latest models (those used by the in its Fifth Assessment Report due out next fall), to estimate seasonal changes in precipitation, evaporation, and in the near future, 2021-2040. "It's a much finer grain picture than the one we had in 2007," said Seager.

Drying is expected in all three regions, as warmer temperatures trigger more evaporation, even in places that may see greater seasonal rain or snowfall, the study found. The models project that temperatures in 2021-2040 will be 1 to 2 degrees Celsius warmer than now. The Colorado headwaters are expected to see more precipitation on average, but annual stream flow is expected to decline by 10 percent, and as much as 25 percent during springtime, as warmer temperatures boost evaporation, the study found. California and Nevada will also see big changes in spring, with a projected 20 percent drop in spring runoff; Texas will overall become drier with a 10 percent decline in annual runoff. For Texas the models predict that precipitation will decrease and evaporation rates will also go down in spring and summer, but only because "there is no moisture to evaporate," said study co-author Mingfang Ting, a climate scientist at Lamont-Doherty.

Population growth in the Southwest is putting added pressure on regional water resources. To put the Colorado flow projections in context, a 10 percent decline is about five times the amount of water that Las Vegas uses in a year, said Udall. With alternate water sources tapped out, the West will likely have to meet the decline by cutting back on water use. "You can't go build another water project," he said. "That's what makes this problem so difficult."

Explore further: Cut the salt: Green solutions for highway snow and ice control

More information: DOI: 10.1038/nclimate1787

Related Stories

Colorado River Basin vulnerable to drought

Feb 22, 2007

A National Research Council study of the Colorado River Basin found that the area could suffer severe droughts as the climate warms and population grows.

Southwest headed for permanent drought

Jan 31, 2011

(PhysOrg.com) -- The American Southwest has seen naturally induced dry spells throughout the past, but now human-induced global warming could push the region into a permanent drought in the coming decades, ...

US southwest could see 60-year drought: study

Dec 13, 2010

An unprecedented combination of heat plus decades of drought could be in store for the Southwest sometime this century, suggests new research from a University of Arizona-led team.

Recommended for you

Nicaragua: Studies say canal impact to be minimal

4 hours ago

Officials said Thursday that studies have determined a $40 billion inter-oceanic canal across Nicaragua will have minimal impact on the environment and society, and construction is to begin next month.

User comments : 14

Adjust slider to filter visible comments by rank

Display comments: newest first

rwinners
3 / 5 (6) Dec 23, 2012
Ah, but just like oil... if the price rises significantly, more water will be delivered.
Do be prepared to pay for it!
XQZME
2.5 / 5 (11) Dec 24, 2012
Expel 2 million illegal aliens and there would be a reprieve.
Caliban
2.5 / 5 (8) Dec 24, 2012
Expel 2 million illegal aliens and there would be a reprieve.


Or, eliminate several million fucktards that feel compelled to wash their cars, trucks, boats, motorcycles and ATVs every few days.

That would help.

VendicarD
2.6 / 5 (5) Dec 24, 2012
The Colorado river no longer reaches the ocean. It's flow is all used up before it gets there.

A reduction in water flow will mean the loss of large amount of agriculture.

As the central U.S. reverts to desert, one wonders how America will be able to feed itself.
Lurker2358
2.3 / 5 (3) Dec 24, 2012
Expel 2 million illegal aliens and there would be a reprieve.

Or, eliminate several million fucktards that feel compelled to wash their cars, trucks, boats, motorcycles and ATVs every few days.

That would help.


Or we could do both. That would help twice as much.

Although actually, if the 2 million use 200 gallons of water each week washing their cars, then that's only 20.8billion gallons per year, or 2.781 billion cubic feet per year.

This comes to 12 hundredths of an inch across 10,000 square miles.
jsdarkdestruction
4 / 5 (4) Dec 25, 2012
Expel 2 million illegal aliens and there would be a reprieve.

"Some 40 million people depend on the Colorado River Basin for water "
i dont see how 38 million people instead of 40 is going to have much of an effect.
Caliban
1 / 5 (2) Dec 25, 2012
Expel 2 million illegal aliens and there would be a reprieve.

Or, eliminate several million fucktards that feel compelled to wash their cars, trucks, boats, motorcycles and ATVs every few days.

That would help.


Or we could do both. That would help twice as much.

Although actually, if the 2 million use 200 gallons of water each week washing their cars, then that's only 20.8billion gallons per year, or 2.781 billion cubic feet per year.

This comes to 12 hundredths of an inch across 10,000 square miles.


Excellent work, there, Lurker.

I think the standard units you are looking for is "Acre Feet" though.

One acre-foot = 325,853 gallons.

20.8 billion gallons ~ 63,832 acre-feet.

That is actually quite a bit of water, my friend.
Nartoon
3 / 5 (4) Dec 26, 2012
The 40M people who use water, as opposed to industry don't actually waste water. Every drop flushed down a toilet/shower etc. goes back into the river cleaner than it came out. The only reduction is for lawn watering.
ScooterG
1.4 / 5 (7) Dec 27, 2012
"Everyone wondered what the next generation of models would say"

Wrong. We all know climate change models are designed to support AGW.
ScooterG
1.7 / 5 (6) Dec 27, 2012
As the central U.S. reverts to desert, one wonders how America will be able to feed itself.


Should our food production decline, likely we'll export less and import more. That will cover our needs `til the weather patterns change again - don't panic.
rwinners
3 / 5 (2) Dec 28, 2012
Scoot along, Scooter. The US now feeds a significant portion of the world population. Where will we import from?
VendicarD
4 / 5 (4) Dec 28, 2012
The universe is well known to have a strongly Liberal Bias.

"We all know climate change models are designed to support AGW." - ScooTard

ScooTard drinks far too heavily and far too often.
VendicarD
4 / 5 (4) Dec 28, 2012
I'm not sure where ScooTard is going to be getting the money to import this food, or where he is going to import it from.

"Should our food production decline, likely we'll export less and import more." - ScooTard

Perhaps he believes that he will be trading earth wompum for space alien wheetabix or something.

Caliban
5 / 5 (1) Dec 28, 2012
The 40M people who use water, as opposed to industry don't actually waste water. Every drop flushed down a toilet/shower etc. goes back into the river cleaner than it came out. The only reduction is for lawn watering.


@nartoon,

not to put too fine a point on it --this simply isn't true. All wastewater that is treated and released back into our waterways is significantly degraded in quality, with considerably increasent loads of bionutrient, chemical, metal, pharmaceutical and other solids --most notably toilet paper fiber-- which is then diluted in the larger volume of waterway flow.

The only decrease of note is in the numbers of active pathogens. You could make the argument that this is an improvement, but it stills comes at a very real cost in terms of water quality.

By the time the Colorado's waters finally evaporate upon the sands of its former delta, they are so laden with waste from "treated" discharges that they have long since ceased being potable.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.