Oceans of water
It’s easy to understand why so many of us, hearing of threats from climate change and shrinking water supplies, turn our gaze west to the mighty Pacific. The Colorado River, a water source strained to its limits, once seemed endless. The ocean practically is endless. As Saudi Arabia and now Australia have shown, it is possible to remove the salt from ocean water and get perfectly decent -- indeed, quite high-quality -- drinking water.
So why not, Southern Californians ask, tap the sea to solve our state’s water woes?
Desalination, as the process of removing salt from water is known, will be an important part of California’s long-term water supply solution. Already the technology is used to prepare wastewater for refilling underground aquifers. Desalinating ocean water could provide cities with new “local” water sources that, unlike the imported water that currently slakes our thirst, wouldn’t be affected by problems in the Sacramento-San Joaquin River Delta or fights over water rights on the Colorado River. Best of all, the ocean is drought-proof.
But as attractive as it sounds, desalination won’t be the saving hand that pulls our lush lawns and alfalfa fields from the jaws of arid reality. It is, and probably will remain, too expensive, too energy intensive and potentially too harmful to the environment to provide most of the water our state needs. By 2030, state water planners predict, desalination is likely to generate just a small portion -- less than 10% -- of California’s water supply. We will still have to conserve.
Desalination plants employ a process called reverse osmosis, which forces a liquid through a filtering membrane to purify it. Unfortunately, the process is very, very energy intensive -- using about 30% more power than the energy-intensive systems already in place. To put this in perspective: The purification systems and massive pumps that today move water throughout the state use almost 20% of all the energy consumed in California. Switching to “desal” on any kind of large scale would burn through one-third more. Generating so much additional energy would be a greenhouse-gas nightmare.
There are other environmental impacts to consider too. Like the intakes of water-cooled power plants, which also suck in water from the ocean, desalination facilities can trap fish and larvae, harming marine life. Every two gallons of seawater processed create one gallon of potable water and another of double-strength brine, which must be diluted before it can be dumped (usually, discharged back into the ocean).
Because of strict development regulations on the coast, acquiring permits for desalination plants is a complicated and expensive process. Poseidon Resources Corp., a water infrastructure development company based in Stamford, Conn., has spent tens of millions of dollars and 10 years on a plant in Carlsbad that will produce 50 million gallons a day -- and it hasn’t even broken ground. If the company gets final approval from the Coastal Commission on Aug. 6, it will spend at least $300 million more on capital costs before it produces its first drop of desalinated water, which won’t be before 2011.
These costs add up -- and get passed on to consumers. Today, treated water purchased from the Metropolitan Water District costs about $500 per acre foot (an acre foot, or 326,000 gallons, is enough water to supply two families for one year). Because the Los Angeles Department of Water and Power is able to supplement MWD water with groundwater at $200 to $250 per acre foot and imports from the Owens Valley at $300 to $400 per acre foot, its water costs even less. Desalinated water costs somewhere from $850 to $900 per acre foot (Poseidon’s estimate for its Carlsbad plant) to more than $1,500 per acre foot (the LADWP’s estimate).
In the short term, desalinated water is unaffordable for Los Angeles -- though it may make better economic sense as imported water becomes scarcer and pricier. In a place like San Diego County, which has few local water resources and depends almost entirely on imported water from the MWD and even more expensive supplies, desal makes a lot more sense. Hoping to lessen cities’ dependence on water from the delta and the Colorado, the MWD offers a $250-per-acre-foot subsidy for water districts for the purchase of desalinated water, which could make Poseidon’s Carlsbad water, for example, almost competitive with imported water (with the added bonus of being drought-proof and therefore dependable).
Because cities must develop local water supplies, we urge the Coastal Commission to grant final approval for the Poseidon plant in Carlsbad, which has been designed to mitigate environmental damage and will offset carbon emissions from the extra energy it consumes as well. We also hope the federal and state governments will continue funding projects such as Long Beach’s experimental desalination plant, which is trying out more energy-efficient methods of purification and is experimenting with bringing in seawater from beneath the ocean floor -- a method used in Japan that may reduce harm to marine life. Any progress in making desalination cleaner and cheaper, and therefore a better option for California, is welcome.
But desalination is just one in a broad portfolio of technologies and strategies that California will have to employ to meet its water needs in the decades to come. Throughout the state -- and especially in Los Angeles, where water is relatively cheap -- conservation, wastewater recycling, storm water capture and other approaches must come first. Desalination isn’t some kind of magic that will allow us to continue sprinkling our sidewalks, hosing down our driveways and taking hourlong showers. Its modest promise cannot become an excuse to waste water. It must be a complement to conservation -- not an alternative to it.