Desalination and water’s scale issue

A sometimes poorly understood piece of the water story is the question of scale – the truly enormous quantities of water required to do human stuff like be a city or grow our food.

This is the shortcoming of well-meaning suggestions like building a pipeline to the Missouri River or a string of desalination plants along the coast, or a string of desal plants that connect up with big pipelines criss-crossing the country.

Writing in the San Jose Mercury-News last week, Stanford’s Leon Szeptycki and Newsha Ajami gave a nice explanation of the problem in the context of California’s ever-present desal discussion:

We withdraw approximately 42 million acre-feet per year from rivers, streams, and aquifers in California. We use up a net total of 33 million acre-feet of that. According to the 2013 update to the state’s water plan, even if every proposed ocean desalination facility were built (an unlikely scenario), they would produce a combined total of approximately 382 thousand acre-feet a year, less than 1 percent of the state’s existing water budget.

This doesn’t mean that desal does not have a place at the margins, in niches where there is no good alternative. But in general the scale of our water use is far too vast to have any impact on the overall problem.

3 Comments

  1. In general, I think that desalination has a kind of mythical quality to it. Here in NM, I’ve heard a USGS engineer say that desalination is “the future” and that there is something wrong with you if you don’t accept that. What makes that crazier is that desalination in NM is being marketed as the saving grace for communities in the middle of nowhere without any other source of water, our brackish water is non-renewable, and the supply is only projected to provide 50-100 years of their water needs. Private companies stand to make a fortune off of a limited resource, the public will suffer, and no one seems to notice.

  2. In California, desalination is always brought up as one spoke in the wheel but its just that. It would take something on the order of 20 desalination plants the size of Carlsbad to equal the amount of water diverted via MET’s aqueduct over a years time. The problem, besides the cost, is where do you put them. You would have to industrialize the coast which isn’t going to happen.

    Conservation and using what we have in smarter ways is the best long term solution.

  3. @Bert Bell, I absolutely concur with your comments! And not to mention the energy needs to run all of those desal plants.

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