Skip to comments.California Irrigation Changing Weather Patterns in American Southwest
Posted on 02/02/2013 11:15:45 PM PST by neverdem
Water diverted to central California's farmlands boosts rainfall in nearby states and may even exacerbate periodic flooding in some regions, a new study suggests. The phenomenon may also be happening elsewhere in the world.
California's Central Valley—an area almost twice the size of Massachusetts where farmers raise more than 200 different crops, including apricots, asparagus, cotton, and grapes—is one of the largest irrigated regions in the world. Every year, several cubic kilometers of water are supplied to the Central Valley's fields, about 60% of it from river flow diverted into the region and the rest from wells. A significant amount of that liquid evaporates from fields rather than nourishing crops, says James Famiglietti, a hydrologist at the University of California (UC), Irvine. That boosts humidity in the valley, according to previous research, but scientists haven't evaluated its effects farther afield.
So Famiglietti and university colleague Min-Hui Lo employed a global climate model. In one set of the team's simulations, no irrigation occurred. In another set, the researchers added a volume of water equivalent to 350 millimeters of precipitation falling on each square kilometer of the valley's fields between May and October, the time of year when soil moisture typically takes a dive if irrigation isn't provided.
The extra moisture boosted rainfall as far away as western Nebraska and the panhandle of Oklahoma, the team reports in Geophysical Research Letters. Most notably, parts of southern Wyoming and the Four Corners states—Utah, Colorado, Arizona, and New Mexico—received between 4 and 14 millimeters more precipitation each June, July, and August. Overall, that boosts summer rainfall in those areas by 15% above average, which in turn increases runoff into the Colorado River by 28%.
But not all of the enhanced rainfall comes from California moisture, the team notes. As water vapor in the air condenses, it releases prodigious amounts of heat. When that hot air rises, it creates low pressure at ground level in the region surrounding the storms and draws in moist air from surrounding regions, including the Gulf of California and the Gulf of Mexico. "The added moisture really fires up the storm cycle" in the Southwest, Famiglietti says.
The new research "offers one compelling answer to the question of what happens to all of the water evaporated from California's Central Valley farmland," says Lara Kueppers, an ecosystem scientist at UC Merced. The Central Valley is just one of many regions globally that are actively and unsustainably diverting surface water and ground water onto agricultural fields, she notes. "To accurately capture the influence of these regions' on the atmosphere, these massive diversions need to be accounted for."
Yet, climate models typically ignore the effects of moisture from irrigation, Famiglietti says. India, China, and the Great Plains area of the United States are just a few regions where irrigation might significantly humidify the air, and regions downwind are likely receiving increased rainfall as a result, he notes.
Such irrigation doesn't just increase rainfall, adds David Changnon, a climatologist at Northern Illinois University in DeKalb. The enhanced precipitation in Colorado, for example, may be boosting the strength and frequency of local flooding events that commonly occur there in late July and early August.
Also, Changnon says, the findings may provide a glimpse of a future in which the American Southwest becomes increasingly parched. If California ever dials back irrigation because of reduced availability of ground water or reduced flow in rivers now diverted to the Central Valley, precipitation throughout the American Southwest could take a dive. A study of rainfall patterns in the Southwest before the 1940s, when irrigation in the Central Valley became widespread, might provide scientists with a better climatic crystal ball.
When your model tells you the unbelievable, throw out your model. The faster the supercomputer used for models the faster and BIGGER the mistakes. Cr@p in equals cr@p out. I seem to remember a small body of water less than 100 miles west called the Pacific Ocean.
Who’s the head Ubangi that get to declare whether something is sustainable or not? Is it the same idiot that declared carbon dioxide to be a pollutant?
I hate to break the news to these clowns, but they may want to take a drive through the Central Valley some day. Roughly half, if not more, of their water supply has been cut off, thanks to critters like Snail Darters, Gnat Catchers, bit turtles, etc.
Maybe in the past the most productive agricultural land in the world had some small effect on climate, but not anymore - it’s practically desert now.
Please don’t bother the “scientists” with “facts”. They left that school behind a long time ago.
Just ask Rep. Nunez about the devastation that Obama/EPA/Dept. of Interior and California has done to the San Joaquin Valley and its once bustling farming industry.
Check on how many thousands of farm workers were put out of jobs because the snail darter etc.
Well, I’m sure these idiots are more than willing to supply a solution. Let me guess. Ban farming where it requires irrigation! Who needs farmers anyway? We can just buy our vegetables at the supermarket.
Here in The Central Valley the irrigation water comes from local rivers which are supplied from winter mountain run-off.
If there is low snowfall in the Sierras, our area farmers do not receive the water needed for crops and the crop yield is deminished. Along that line of thinking the snail darters must receive the water to survive and damn the farmers.
This year, snow and rainfall have produced an abondance of water which will flow through the valley rivers and thus to the local farmers.
But, no matter how much water flows, the useless snail darters will get their water and farmers will lose in the process.
What Difference Does That Make?
Not a big deal really.
All the pools in the L.A. area have caused the humidity level to raise there.
Oh yeah, like the Pacific Ocean affects humidity. That’s crazy talk!
I seem to remember a small body of water less than 100 miles west called the Pacific Ocean.
Exactly. Irrigation hardly puts out enough climactic moisture tio compete with the sweat on an India Elephants Arse.The Ocean is the major driver along with general wind direction, and the sun.
These envirinmentalists are like a male mouse floating down the river laying on a shingle with a hard on, yelling , “ RAISE THE DRAWBRIDGE!”
Its beyond ludicrous.
I’ve been talking about how moisture is carried across the land for five or six years now. I don’t know about the numbers, but the effects are real.
The way most of the farmers in that area irrigate is with impact sprinklers. There is a great deal of loss on a windy day, which is usual. Between that and the evaporation off the leaves the farmer loses 15% of what is ejected from the nozzle. Considering the acreage, that's a lot of water.
The greenies will blame the farmers for the persistence of Bromus madritensis in that Mojave region as displacing native wildflowers, seeing as they haven't a either the clue or the inclination to do anything effective about it.
Considering the acreage, that’s a lot of water. >>>>>>>>>>>>>>>>>>>>
No it is not. Its actualy less than a drop in the bucket
of the earths regional weather system.
Thats why it is ludicrous.
Seem to remember reading that the cental valley was impassable until late summer most years because Tule lake occupied most of the valley floor. William Brewer wrote extensivly of it in his travels as the state surveyor 1851-1854. Ferrys were used between Yurba Buena (San Francisco) and Sacramento because land travel was by way of Bakersfield.
I think even Kit Carson and Fremont both talked about valley crossings being cirquitus.
Some years ago, a “genius”-type scientist and inventor wondered why severe deserts can go right to the beach of an ocean, yet have almost no precipitation.
He discovered that ocean water has a 2-3mm thick layer on top of it that is much warmer than the rest of the water, and it somehow blocks evaporation from the surface.
But if you sprinkle some water mist and droplets on this upper layer, it temporarily breaks it up, and the amount of evaporation jumps.
So he had the idea of putting 20-30 vertical wind turbines on floating rafts several miles off a desert coast. As the wind turned the turbines, they would pump water up many feet, to spray a heavy mist into the air, which would then descend over a wide area to break up the 2-3mm warm water layer.
Thus much more evaporation would come from the ocean, and it would significantly increase precipitation inland.
Those correct dates are from 1860-64 and he was working for the US Geological Survey under Josiah Whitney (it is available online here). His diary (I have it in front of me) emphasizes a particularly wet set of years due to the great flood of January 1962, which would skew his observations for years thereafter. If I recall correctly, he went down to the southern Sierra the year after the flood.
Hand-wave. Numbers and sources please or I won't bother with you again. What I'm talking about can be found in any grade-school science page.
Much of the rain that falls in dry areas evaporates before it hits the ground (you can see it). If it does make wet surfaces much of that evaporates after the shower, or is transpired from vegetation. That fraction does not run off or sink to the water table; it rises back into the atmosphere to form clouds to be carried farther and redeposited. So to presume that when rain falls inland, all the water that fell must have come from the ocean is totally erroneous. A substantial fraction has cycled across the landscape (varying with both topography and vegetation).
Frankly, I see the effects cited in the report as a good thing, an effect that could help us transform much of the Great Basin back into a productive savannah instead of the sagebrush wasteland it is today. Without dams and irrigation, that region would be the borderline desert it was before those farms were developed (albeit with heavily subsidized water delivery).
This whole fight over water in the southern San Joaquin Valley is in reality a set of competing real estate scams. I don't like any of the big players involved; they're all government whores. The California Aqueduct moves more water in late summer than the flow of the San Joaquin River would have been without the dams. The bulk of that water evaporates. It's a lot. Don't get me started about soils, vegetation, aboriginal burning, trace mineral composition and albedo when it comes to retaining water in topsoil. Those soils are LONG gone. We don't have that system any more.
I'd go all the way and hope for a really big fishin' hole!