Revisiting Desalinization

Much of the water in Southern California comes from the north, and to get into the Los Angeles basin must be pumped over the Tehachapi Mountains. This is the biggest water lift in the world, about 2,000 feet (ref. NRDC).

When looking at alternatives to transporting huge quantities of water that might be better left where it is, desalinization is not getting sufficient attention. It turns out that 2,000 feet of lift is about the point where the energy necessary to desalinate seawater is actually slightly less than the energy required to pump water over a 2,000 foot mountain.

In our features “India’s Water Future” as well as “Arctic to Aral,” we have reported on the energy requirements to pump water. Using the same formulas, it turns out that the energy required to lift a cubic kilometer of water 2,000 feet is 248 megawatt-years.

What if that water were desalinated in plants located on the Pacific Coast, perhaps using land within Camp Pendleton between Los Angeles and San Diego? As we reported in “Photovoltaic Desalinization,” desalinization plants able to process 1.0 cubic kilometers per year are being designed today, at an estimated cost of $2.0 billion dollars. At an operating energy requirement of 2.0 kilowatt-hours per cubic meter, it would take 2.0 billion kilowatt-hours to desalinate one cubic kilometer of seawater. That’s only 228 megawatt-years, LESS energy than is used to pump the same amount of water into Los Angeles from the north.

According to the Los Angeles County Dept. of Water and Power, the average residential household in LA County uses 500 gallons of water per day (ref. LADPW). That equates to 690 cubic meters per year, which means that 1.0 cubic kilometers of water would supply nearly 1.5 million households with water – well over five million people.

For every gallon of usable water extracted from seawater, seven gallons of slightly more salinated seawater must be returned to the ocean. The costs for a system to distribute this water in a sufficiently dispersed stream certainly wouldn’t cost more than the desalinization plant itself. Assume a cost of $5.0 billion for a desalinization plant that would supply water to 5.0 million people. Amortized over 50 years, this capital cost would only amount to about $20 per person per year – adjusting for present value of money, certainly no more than $50 per person per year – not much.

What water crisis? What water shortage?

Categorized | Energy
One Response to “Revisiting Desalinization”
  1. I wasn’t aware of the additional cost of distributing the saltier water back. How much of an impact does that water have on the environment if not dispersed? As in, what happens if you just pump it back in one location? How would you disperse that kind of volume?

    By the way, I’m for desalinization. I think it’s a great idea and something we need to build now, not when water is in short supply. I’m just curious about this aspect of the problem that I was unaware of before.



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