Maybe it started last Jan, when California Governor Jerry Brownish said that his state would need to cut back its water use by 20% or confront "terrible consequences." Or maybe it was in Baronial, when the boondocks of Due east Porterville literally went dry, forcing the country to truck in h2o to residents so they could accept flushing toilets. Or perhaps information technology was in September, when a scientific study noted that the worst for California was yet to come: an epic "megadrought" that, says one researcher, could exist "worse than anything seen during the last 2,000 years."

Whatever the turning point, by this autumn information technology was apparent that the future health of California was in jeopardy. The state'southward vaunted tech culture can exercise a lot of things, but it tin't go far rain.

Or can it? As California's drought worsened, only northward of San Diego a massive seawater desalination constitute–that is, a constitute that sucks in ocean water, filters out the table salt, and then pumps the resulting freshwater into municipal pipes for residents to apply–moved closer to completion. The Carlsbad plant, equally it'due south known, will price $1 billion and volition exist up and running by late adjacent year. Its toll, energy requirements, and potential environmental bear on accept been debated for a decade. When it finally comes online, though, Carlsbad will produce 50 million gallons of freshwater every day, making it the largest desalination plant in North America. What's more, the institute volition demonstrate something vitally important to the rest of California, likewise as to residents of America's south and southwest, who also happen to be suffering through devastating droughts: For the commencement fourth dimension in decades, a substantial new source of drinking h2o will be added to a system that has been running lower and lower each year.

Nevertheless, Carlsbad won't come up shut to slaking California's thirst, especially every bit climate change threatens to further erode its freshwater supplies. The projection is for the plant to supply well-nigh vii% of San Diego's drinking water. It is, so to speak, merely a few very expensive drops in the saucepan. And that has left a question on the minds of many drought-stricken Californians: With ocean water all around, why can't more–or amend–engineering science solve this trouble?

One of the most inconvenient facts for humanity is that about 97% of the water on earth is saltwater–non all of information technology as briny as the Atlantic or Pacific, but to varying extents clouded by minerals that make information technology as well brackish to beverage or employ for agriculture. But we're besides lucky. The earth works like a big desalination plant: Freshwater evaporates from the oceans; the vapor collects in clouds; and it falls every bit rain or snow that in time is nerveless in reservoirs or runs back to the ocean. Oceans are salty, in fact, because rainwater combined with minerals from land and then poured into the sea over hundreds of millions of years.

For decades, the principal technology for desalination worked a lot like this natural process: Engineers congenital plants that could heat up huge pools of seawater then that freshwater evaporates, gets captured, and is then directed into a municipal water supply. Many of these plants notwithstanding exist–near notably in the Middle East, which has relied on desalination for decades. But in the early 1960s, some scientists at UCLA came upward with a new blazon of filter (or membrane, every bit information technology's known in the business) that made a better kind of desalination process, known as opposite osmosis, or RO for short, viable. Essentially, ocean h2o could be pumped through the membrane at a pressure around xv times what comes out of your faucet at home. What passes through is freshwater. What doesn't go through is the salt, which is diverted and sent back to the ocean.

Over the past l years, RO systems accept become a fixture in the h2o business. They're used in big seawater plants like Carlsbad and in ordinary water-handling plants, on yachts and submarines, and as a crucial step for industries (such as pharmaceuticals or loftier-tech) that crave exceedingly pure h2o for manufacturing. An RO membrane is now a commodity that costs almost a dollar a foot. "It will remove 99.viii% of the salt and last v years, or in some cases 10 years," says Tom Pankratz, an industry veteran and desalination analyst. "There may be some small improvements to come, only we're not going to go a whole lot cheaper, in my opinion."

Down the drain: What remains of Shasta Lake in Lakehead, Califronia, which is at thirty% of its normal capacity.Photograph: Justin Sullivan, Getty Images

This is some other way of proverb that RO is a "mature applied science." Information technology's a term that repels California's entrepreneurs and venture capitalists, who adopt to focus on the heady prospect of a startup that volition meliorate an existing technology by, say, a factor of 10. Recently, there have been calls in California newspapers for entrepreneurs like Elon Musk to apply their talents to the desalination game, just it'due south almost certainly the case that water is a specialty technology that is beyond the reach–and, probably, the interest–of nigh mavericks or upstarts. "When you expect at the cardinal corporeality of free energy for desalination, in that location isn't that much difference betwixt what they're doing now and the amount of free energy that is theoretically required," says Tom Davis, who runs the Center for Inland Desalination Systems at the University of Texas at El Paso. Davis says that the trend now is to create filters from a new, wondrously hard material known equally graphene. But he is skeptical. He has peered down the pipeline, he says. "And I have not encountered a revolutionary technology."

The difficulty of improving water systems is akin to the difficulty of irresolute energy or transportation systems: the existing technologies are and then well established that it'southward economically difficult to innovate anything new–or anything risky. For instance, "frontward osmosis" is a new idea in the water biz. Rather than pushing saltwater through a membrane, it allows the natural concrete properties of water to separate the salts out without a high-pressure process. Several U.S. startups, near notably the Boston firm Oasys H2o and a Bay Expanse startup called Trevi Systems, are at the forefront of this technology. The upside is the process uses less energy and is–at least theoretically–less expensive. (The downside is that an MIT study recently cast uncertainty on the energy savings.) Forrard osmosis is nevertheless being adjusted in pocket-sized, experimental plants, such as one that Trevi is involved with in the United Arab Emirates. And so even if it works, it might accept years earlier it'southward widely implemented.

But it may be the case that big leaps forward come up from changing the components inside desalination systems and not merely by changing the procedure itself. One Danish company, Aquaporin, has begun manufacturing membranes that mimic the function of the human being kidney, with provocative results. Located in a gleaming new edifice at the border of the Academy of Copenhagen, Aquaporin is led past a immature Danish scientist named Peter Holme Jensen. "When we started in 2005," Jensen explains, "we said, 'Allow'south attempt to exploit and reuse nature, considering if nosotros're looking for sustainability, we don't think we can do better than nature.'" These membranes–they wait and feel a lot similar thin sheets of white paper, with a glossy blanket on superlative–can be employed in systems that use either opposite osmosis or frontwards osmosis. (Shortly, they will be tested by NASA as a style to recycle wastewater in space; as Jensen says, yous can actually pee through its membrane and drink what comes out the other side.) The membranes could eventually reduce the costs of desalination past peradventure as much as 15%. In an industry where very little changes, that would be transformative.

If the water industry were like the pharmaceutical manufacture, Jensen says, "it would be every bit if they hadn't invented a new drug in xxx years." Inside such a bourgeois marketplace, he adds, information technology may take years earlier his applied science tin have a big impact. That would likely be too far in the future to solve California's immediate h2o problems. And not everyone thinks of desalination as the simply solution to how some regions are "drying out." Heather Cooley, of the Oakland-based Pacific Institute, notes that the Carlsbad plant will non just create a new freshwater supply that costs well-nigh double the corporeality Southern Californians already pay for water, but could potentially have a rebound effect. Some plants–in Australia and in Florida–have come online, just to observe they aren't completely necessary. In some cases, drought situations can ease; at other times, a higher price of water from the desalination process can incite consumers to use less, thus obviating the need for a big, new supplemental found in the beginning place. "At that place tends to be a risk in building desal plants that are also large, or building them also presently," Cooley says.

In that location's as well the potential that a establish may significantly impact fish populations harmed by the intake pipes or the supersalty discharge from the desalination procedure. However, experts similar Pankratz see it as an inevitable choice. "Desalination is like insurance," says Pankratz. "The water situation is pretty bad in Southern California. Merely until things hit catastrophic proportions, people are going to be talking most how expensive desalination is and how much free energy it uses." Eventually, he says, they'll be set to pay–because by then, in that location may exist no other options.