For decades, sewage has been treated and used for irrigating crops, parks, and golf courses, but making it fit for human consumption requires a much more rigorous filtration technology using polymer membranes. No thicker than a human hair, the membranes are at once delicate and durable. Using pores smaller than one-millionth of a millimeter, they’re capable of wiping out microscopic contaminants. ... the water division at Dow Chemical, he pulls in more than $1 billion in sales annually. The membrane market is growing more than 10 percent a year in part because of increasing water scarcity worldwide and ever more pressure to develop drought-proof water supplies from new sources. ... The whole concept of recycled sewage might be harder to swallow if there weren’t already so much sewage in the water sources we routinely draw from. ... the very reason chemists created these synthetic membranes decades ago is that, increasingly, humans have been contaminating the water supply. Industries have emerged, meanwhile, that need purer water for manufacturing. Most major players in the automotive, beer and wine, food processing, petrochemical, pharmaceutical, and semiconductor industries, for example, rely on water purified by membranes. ... recycling wastewater is about half the cost of desalinating ocean water: Both use RO membranes, but the salinity of ocean water is much higher, so it’s harder and much more energy-intensive to pump it through the tiny holes.
Since 1960, tens of millions of people have migrated toward the Pacific, settling in Las Vegas and Tempe and Boulder. Denver has tripled in size. Phoenix, having added some 3.6 million people, has more than quintupled. Today, one in eight Americans depends on water from the Colorado River system, and about 15 percent of the nation’s crops are grown with it. ... the demands on the river were never sustainable. In 1922, the seven states in the Colorado River watershed signed a compact dividing its water. With little historical data, they calculated the river’s capacity after a decade of unusually wet conditions. ... Since the current drought began, in 2000, that shortfall has averaged 25 percent. Instead of adjusting their allotments, states have drawn down the nation’s largest reservoirs, which are quickly draining. Even this winter’s El Niño weather pattern won’t bring enough rain to restore the region’s supply ... To determine who gets water and who doesn’t, states rely on a system that originated more than 150 years ago—when water was plentiful and people were scarce. ... “prior appropriation,” which promised rights to use a share of water based on who got there first. ... Prior appropriation became the foundation of western water law, and it established order in the West. Today, though, state water laws are largely to blame for the crippling shortages. Because water rights were divvied up at a time when few cities existed west of the Mississippi, some 80 percent of the region’s water goes to farmers, leaving insufficient supplies for growing cities and industries. And farmers must put all their water to “beneficial use” or risk losing their allotment—a rule that was originally intended to prevent hoarding but that today can encourage waste. Many farmers have not adopted modern technology that can cut water use by up to 50 percent, in part because they need to protect their water rights. ... Allowing people to buy and sell water rights is a more expedient way to redistribute the West’s water, he argues. Waste would be discouraged, water would shift to where it’s needed most, and farmers would be compensated. ... The West would have plenty of water if people used it more wisely: Most of the region’s supply goes to growing low-value, water-intensive crops such as hay and alfalfa—in many cases in the desert.