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11 Trillion Gallons of Water Needed To End California Drought
mrflash818 points out a new study which found that California can recover from its lengthy drought with a mere 11 trillion gallons of water. The volume this water would occupy (roughly 42 cubic kilometers) is half again as large as the biggest water reservoir in the U.S. A team of JPL scientists worked this out through the use of NASA's Gravity Recovery and Climate Experiment (GRACE) satellites. From the article:
GRACE data reveal that, since 2011, the Sacramento and San Joaquin river basins decreased in volume by four trillion gallons of water each year (15 cubic kilometers). That's more water than California's 38 million residents use each year for domestic and municipal purposes. About two-thirds of the loss is due to depletion of groundwater beneath California's Central Valley. ... New drought maps show groundwater levels across the U.S. Southwest are in the lowest two to 10 percent since 1949.
GRACE data reveal that since 2011, farmers raising water-intensive crops in barren desert soil caused the Sacramento and San Joaquin river basins to decrease in volume by four trillion gallons of water each year (15 cubic kilometers).
I wasn't real thrilled with the linked article. All it did was call out a number with nothing to scale it against.
A real quick search brought up an estimate of three years worth of rain like this would be needed to make up for the drought and also had some other ways of relating what 11 trillion gallons actually means as precipitation received is traditionally measured in inches.
http://www.cbsnews.com/news/wh...
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Is that a lot? I mean compared to rainfall over that area.
It is about 10cm or 4 inches spread over the entire state.
There are 264 gallons per cubic meter. So 11 trillion gallons is 4.16e10 m^3. California has an area of 424,000 km^2, or 4.24e11 m^2. So divide the volume by the area, and you get the depth = 4.16e10/4.24e11 = 0.098 m or 9.8 cm or about 4 inches.
I live in San Jose, and we have gotten more than 4 inches of rain in the last week, and it is still raining. There are areas of California (the Mojave Desert) that get a lot less, but also areas (the North Coast) that get a lot more.
Most of California isn't desert, only parts of Southern California. As an example, the Central Valley, the state's biggest agricultural area isn't, nor are the wine growing areas near San Francisco, and yet, they're being hit by the drought just as badly.
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They have been taking water from somewhere for a long time, cant they just take more of someone else' water in order to live in a desert?
Hey, the USA is a large and sparsely populated country.... How about you try living in some of the more habitable areas?
Nobody lives in the California Desert. Well, okay, we do have a decent retirement community out in Palm Springs, but the parts that most people settled on were temperate grasslands, forests, and wetlands (the Central Valley was an inland sea for much of the year before we dammed it all up).
The real problems are:
1) Irresponsible farming by agribusinesses. This one here is the biggie, but is really hard to control because the biggest agribusinesses have so much political clout, both here and in Washington.
2) 150 years of politics. For well over a century, the saying has gone, "Liquor is for drinking; water is for fighting." There are a byzantine set of local, regional, statewide, interstate, and international laws governing how water is used everywhere in the state, most of it based on environmental studies decades or centuries out of date, and none of it changes quickly.
3) Wetland destruction. For a long, long time nobody understood the value of wetlands in water table control, flood prevention, and ecosystem management, and so much of it was filled in and paved over in the last 100 years. This has proven to be a huge mistake, one that will take decades and billions of dollars to fix, and isn't helped by ignorant jackasses who insist that environmental concerns don't exist, that scientists are hucksters, and that God will provide everything we could ever want, forever.
4) Climate change. The theory is nearly 200 years old; the lab-scale proof is over 150 years old; definitive proof it's happening out in the environment is over 50 years old. It's happening, right now, and given politics and the endless prattle of ignorant jackasses it doesn't look like it's going to be slowing down any time soon.
Did you notice what's not on that list? Cities. All of the urban and suburban development in California accounts for less than 10% of the state's annual water usage (the vast, vast majority is used for agriculture), and the number is dropping every year, as more efficiency and water recycling programs come online.
They've been doing that for years in my city to brackish water to supplement the water supply. The problem is that these last few years have been exceptionally dry. You can't just build desalination plants overnight, especially for the amount of water we're talking about, plus it needs to be transported quite a distance and is very expensive. Most of the water is used for agriculture. California produces around 1/3 of all of the food in the country.
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Sure, over-use is a problem, but there's also less precipitation than is normal.
See the scary map here:
http://droughtmonitor.unl.edu/
The weekly update for California says:
Locally heavy precipitation fell across portions of the state this past week. Amounts ranged from 1-6 inches (liquid equivalent) across a large portion of northern California, and parts of the central and southern coastal areas. Up to 3 inches of precipitation (liquid equivalent) was reported in the southern Sierras. However, snow pack remains well below-normal in many areas due to the relatively mild temperatures associated with these storm systems. In addition, much more precipitation is needed to replenish lost reservoir storage. There are still deficits in the conservation pool of millions of acre-feet in the Shasta and Oroville reservoirs north of Sacramento. Oroville reservoir gained about 100,000 acre-feet of storage in the recent storm, returning to one million acre-feet in storage capacity. The capacity of this reservoir is 3.5 million acre-feet, with a flood reserve space of 750,000 acre-feet. Well to the south, last week’s storm produced several inches of rain for San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties. However, this was not enough to generate runoff in natural streams and therefore did not provide any benefit to surface reservoirs. Since the start of the Water Year (October 1), almost all precipitation gauges in the area are still running below normal. No revisions were made to the California drought depiction this week. With the anticipation of another significant precipitation event in the short-term, alterations could be required next week, pending resulting impacts.
Actually, the main crop that is quite profitable but requires vast amounts of water is not rice, but nuts, specifically Almonds. Rice isn't a problem because the delta around the Sacramento river normally floods, so it doesn't take a ton of effort to rice farm up there. The issue is irrigating both snowmelt and river water to the central valley to grow almonds and other crops.
It's less than a dollar a day per person, problem solved. Truth is no one wants to solve the water problem.
http://en.wikipedia.org/wiki/E...
"Still, according to the U.S. Geological Survey, thermoelectric power generation accounts for only 3.3 percent of net freshwater consumption with over 80 percent going to irrigation."
I'm not sure the use in power is as bad as you assert.
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Technologically the plant designs are almost identical. Both are a reverse osmosis design using pressurised water driven up against a membrane. Modern desal plants are actually quite energy efficient, just not as efficient as AWT plants. And the only reason AWT plants are more efficient is that the input water actually has less impurities than salt water.
The other benefit of AWT plants is you get high nutrient biosolids from it that you can then use as fertiliser. Note this is ONLY the case if the AWT sits down stream from a standard waste water plant. If it doesn't and you do an all in 1 process the solids are contaminated with nasty stuff from the medicines we consume which means it is restricted in its use.
I will add to point 2.
The Gold Coast Desal plant is a 125ML RO plant and the brine is returned to the ocean. Testing has shown that you can't detect the increased salt content when more than 20m from the outlet pipe.
The biggest problem with people who think it will increase salinity of the oceans is their inability to grasp the scale of the ocean vs what is removed.