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The Ocean Isn't the Answer in California

Desalination plants are a really expensive way to get more water.

Whenever there’s a drought in California, a seemingly obvious source of new water supply beckons. The state abuts a giant ocean. Why not just take the salt out of some of that seawater? It’s the high-tech, forward-looking thing to do, right?

It’s also the really expensive thing to do. Of all the options for increasing the state’s water supply considered in a report out Thursday from the Pacific Institute, an environmental think tank based in Oakland, California, desalination costs the most per acre-foot (325,851 gallons, 1.2 million liters) of water produced:

source: pacific institute

As is indicated in the above chart, water conservation measures are generally the best deal. Some even have negative costs -- the savings from paying less for water more than offset the cost of a new shower head or restaurant ice machine. The two different landscape conversion estimates, in case you were wondering, are based on whether replacing your lawn with non-thirsty plants costs $2 a square foot (low) or $5 a square foot (high).

All the potential sources of new water supply that were examined actually do cost something, but the numbers compiled by the Pacific Institute’s Heather Cooley and Rapichan Phurisamban show that the price can vary -- a lot. The non-seawater sources all involve using water that’s already available on land and, if necessary, cleaning it up. Plants that desalinate brackish groundwater (of which there were 23 in California as of 2013) or filter treated sewage (there’s one huge one in California’s Orange County that I wrote about last year) often use the same reverse osmosis process that’s at the heart of modern seawater desalination plants. But brackish groundwater and treated sewage have less salt and other junk in them than seawater, so it costs less to make them drinkable.

Desalination still makes sense for some coastal communities cut off from California’s rivers, reservoirs and aqueducts. Santa Catalina Island in Southern California has been desalinating seawater since the early 1990s, and a big new desalination plant opened last December in Carlsbad just north of San Diego. But again, it’s expensive: the San Diego County Water Authority has committed to buy water from the Carlsbad facility for the next 30 years for $2,100 to $2,300 an acre-foot (with adjustments for inflation). By comparison, surface water from the Metropolitan Water District of Southern California costs a bit more than $900 an acre-foot.

That surface water might not be as available in the future, and technological progress may cut the cost of desalination. But the “atmospheric river” of rain and snow bearing down on Northern California this weekend is an apt reminder that the state usually gets so much precipitation that treated seawater, while a welcome supplement at some times in some places, is probably never going to be a major water source. This is something that would-be California water saviors, such as William Shatner with his idea of a pipeline from Seattle or the guy who wanted to ship in Alaska water by tanker, have repeatedly failed to grasp. Most of the time the state has so much water, available at such low prices, that high-priced alternative sources generally aren’t going to be economically viable.

The economics are different in Israel, or on the Arabian Peninsula, where fresh water is much scarcer and desalination has become essential to modern life. But along the Persian Gulf, where large-scale desalination first took off in the 1980s, there are worries that it may be nearing its limit. From a Guardian article last month:

Gulf states are heading for “peak salt”: the more they desalinate, the more concentrated wastewater, brine, is pumped back into the sea; and as the Gulf becomes saltier, desalination becomes more expensive.

An ever-saltier Gulf may not be great for marine life, either. The Gulf is a unique body of water, shallow and connected to the ocean by only a 21-mile-wide strait, so such issues seem far less urgent for desalination plants on the Mediterranean, the Pacific or the Gulf of Mexico. But this is an indication that desalination isn’t a free lunch.

What is a free lunch? The closest thing in California seems to be replacing lawns and water-hungry gardens with less-thirsty landscaping, which according to the Pacific Institute study could save between 870,000 and 2 million acre-feet of water a year. (By comparison, the state’s total urban water use averages about 9 million acre-feet a year, and the capacity of the Carlsbad desal plant is 56,000 acre-feet a year.)

This is sometimes easier said than done: Anna Scott has a revealing story in Bloomberg Businessweek this week describing how Metropolitan Water District lawn-removal subsidies enriched a fly-by-night landscaping firm that covered lots of Los Angeles-area front yards with unsightly (and environmentally problematic) gravel. But in general, the most sensible sources of new water for thirsty California are the ones closest to home.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

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