California's Water System

We’ve just waded through the “California Water Plan,” 2005 update, which is produced by the California Dept. of Water Resources and is the most comprehensive source available on California’s water. Some interesting facts pop out immediately:

California has the most extensive system
of water reconveyances in the world.

(1) Here are the overall quantities: In a normal year, about 250 cubic kilometers (henceforth noted as km3) of fresh water are delivered to California, nearly all of it rainfall, with the only noteworthy exceptions to rainfall being the Colorado River aqueduct delivering 6.6 km3, and the Klamath River delivering 1.9 km3. The rest is rain.

Of this 250 km3 water supply, about 50 km3 goes into the ocean, about 100 km3 evaporates or percolates, and about 100 km3 is used by civilization. And of that 100 km3 that is diverted and used, about half is diverted for “environmental” uses – preserving the environment of the delta for example. Agriculture uses 40 km3 of water per year in California, and urban users consume 10 km3.

If you review the contents of the State report, you will note they prefer the term “million acre feet.” One million acre feet is 1.23 km3. We find km3 far more practical – it helps us grasp the scale of the California water system relative to other parts of the world, and it helps us relate large units to small ones more intuitively. One km3 is one billion cubic meters (m3), which in turn is 1,000 liters. Try doing that with cubic miles, millions of acre feet, or gallons…

(2) What a plumbing system! Reviewing the map provided in the report (Chapter 3) every year, 7.6 km3 of the annual 30 km3 flow of the Sacramento River is sent into the aqueducts of the California State Water Project – most of it for agriculture in the Central Valley. From the Owens Valley, east of the Sierra crest, 2.1 km3 are diverted into the Los Angeles Aqueduct. From the legendary Hetch Hetchy Valley, nearly 1.0 km3 makes its way to urban users in the San Francisco Bay Area. And every year, 6.6 km3 (as noted) comes in from the Colorado River, mostly for agriculture in the Imperial Valley – but combining with water from the California Aqueduct, some 3.7 km3 of this water from the north and from the east make the 2,000 foot lift over the Tehachapi Mountains into the Los Angeles Basin.

(3) There is a lot of above-ground water storage already in place, and groundwater storage appears to have a great deal of potential. Existing reservoirs in California provide for storage of just over 50 km3 of water. Groundwater storage is not yet comprehensively assessed. In the report (Chapter 4), there is a map of California with shaded areas denoting land with subsurface water storage – and every valley and lowland, including all of the vast Central Valley, and also nearly all of the vast areas to the south and east – are apparently atop groundwater resources.

The report provides incomplete information on California’s overall aquifer capacity, for example, it states “over a period of years, artificial recharge in these areas (Southern California) has increased the water now in groundwater storage by about 7 million acre feet (8.6 km3).” The report goes on to say there are another 11 km3 of groundwater storage that could be developed in California. It appears the potential groundwater storage capacity in California greatly exceeds current surface storage.

(4) Bring on desalination! Without going into the derivations, the information in this report (Chapter 6) suggests the capital costs for desalination plants are about $800 per consumer. Amortized over a desalination plant’s useful lifetime, this does not add all that much to the water bill of an urban consumer. As for power consumption to desalinate water – it is now reliably down to 4.0 kWh per cubic meter. Put another way, if you burned an 85 watt bulb year round, that’s all the electricity it would take for one person to desalinate all the fresh water they need. Not much.

Categorized | Consumption, Electricity, Other
2 Responses to “California's Water System”
  1. Brian Hayes says:

    Sorry if I double post.

    In July 2007, the public utility branch of the Singapore government reported the world’s lowest cost to desalinate part of its water supply at US53 cents per cubic meter.

    They’ve replaced the conventional 8 inch process pipe with a new 16 inch reverse osmosis system. Singapore imports more than half it’s water under expiring contracts from Malaysia and is looking toward water independence.

    Does this new cost factor reflect your impressive challenge to examine desalination?

    I call your work “The Tehachapi Calculation”!! :-O

  2. I grew up in San Diego and remember the Point Loma desalinization plant that was moved to GITMO in 1964. I now live in the Carlsbad, CA watershed and have watched the decades long process of trying to get a desalinization plant through the environmental process. Outside of trying to find a way to lower coastal impacts, desalinization is a very energy intensive process. The real issue is that under Cap and Trade there is no way these cost numbers will work. The San Diego Water Authority has vested San Diego’s future, wisely I believe, in desalinization and envisions, I believe, 600 million gallons a day production from three plants (Carlsbad’s 50, 200, and 400). I believe that Cap and Trade will end any possibility of this being achieved unless nuclear power is considered. Given the political atmoshpere I don’t know if that is a possibility.


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