The Coming California Water Boom
California might be in the middle of its worst drought in 1,200 years, but it's also uniquely suited to take advantage of recent advances in small-scale, solar desalination technology. If there's one thing California has plenty of, it's sun, and a recent project funded through state Proposition 50 has proven the viability of zero-discharge desalination and water reuse via concentrated solar stills.
Unlike conventional desalination, which uses high-pressure reverse osmosis to separate water from solids, concentrated solar stills focus the sun's energy with parabolic mirrors to accelerate evaporation inside an enclosure -- distilling fresh water and leaving solids behind.
A recent experiment was conducted on the west side of the San Joaquin Valley, demonstrating that solar energy could make desalination affordable, sustainable, and scalable. Researchers built and continuously operated a solar desalination plant, reclaiming over 93% of the subsurface drainage water, while minimizing or eliminating brine discharge (the salt removed as a solid “co-product").
With concentrated solar stills, an acre of land in California can generate 60-80 acre feet of water per year; this is up to forty times the per acre water consumption of an average California crop (~2 AF/yr). This means that an acre of solar desalination can satisfy the water needs of forty acres of irrigated farmland. That means only two percent of the land needs to be dedicated to water production. With access to an abundant source of saltwater, an area encompassing two square miles would provide 100 million gallons per day; sufficient fresh water for a city the size of Las Vegas (600,000 people).
The result could mirror what has happened in energy generation; rather than relying on large-scale, centralized plants, smaller “distributed” desalination projects across the state could free up hundreds of thousands of acre-feet of water through reuse, reducing overall demand on the water grid. Irrigated farmland is the single largest use of water in California, and adopting concentrated solar stills could drastically increase water reuse -- and go a long way to making agriculture in California sustainable.