The Salton Sea is a vital, threatened link between the Colorado River and coastal cities. Photograph by Claire Martin / INSTITUTE

There is a place in the California desert where a pipe pokes out from a berm made of broken concrete and delivers freshwater to a dying sea. I stood there recently, on a beach of crumbled barnacles, and watched it gush. The sea was the dull blue of a cataract, surrounded by small volcanoes, bubbling mud pots, and ragged, blank mountains used for bombing practice by the Navy and the Marines. The air smelled sweet and vaguely spoiled, like a dog that has got into something on a hot day. When the wind blew, it veiled the mountains in dust and sent puckered waves to meet the frothy white flow from the pipe. The sea, which is called the Salton Sea, is fifteen times bigger than the island of Manhattan and no deeper in most places than a swimming pool. Since 1924, it has been designated as an agricultural sump. In spite of being hyper-saline, and growing saltier all the time, the sea provides habitat to some four hundred and thirty species of birds, some of them endangered, and is one of the last significant wetlands remaining on the migratory path between Alaska and Central America.

In early April, the governor of California ordered the state to conserve a million and a half acre-feet of water in the next nine months, a drastic response to an intensifying four-year drought that has devastated small communities in the north, decimated groundwater supplies in the Central Valley, and made the cities fear for the future. To achieve this savings, Californians are starting to forgo some of the givens of life in modern America: long showers, frequent laundering, toilet-flushing, gardening, golf. It can be hard to visualize a quantity of water. An acre-foot is what it takes to cover an acre to the depth of twelve inches: some three hundred and twenty-five thousand gallons. A million acre-feet is about what the city of Los Angeles uses in two years. A million acre-feet, give or take, is also how much runs off to the Salton Sea each year from the farms of the surrounding Imperial Valley. Salty, spent, and full of selenium and phosphates, the excess water flows down to the sea, where, two hundred and thirty feet below sea level, it evaporates under a blistering sun.

With the state turning brown, the eye is drawn to the bright-green place with the enormous wading pool. A hundred and thirty-five miles east of San Diego, the Imperial Valley has a population of a hundred and eighty thousand, and about five hundred thousand acres of farmland. It was settled as an agricultural area in the early twentieth century, and holds senior rights to water from the Colorado River. California’s share of the river was divided in accordance with the doctrine of prior appropriation: whoever first put the water to “beneficial use” could continue to claim it, so long as they did not waste. Of the 4.4 million acre-feet of Colorado River water that California is normally entitled to each year, the Imperial Irrigation District’s allowance is 3.1 million. Alfalfa is the most widely planted crop, followed by Bermuda grass and Sudan grass, and flood irrigation is typical. A third of the hay is exported to China and to places lacking the land or the water to grow grass—the United Arab Emirates, Saudi Arabia, and Japan—where it feeds dairy cows and the cattle that produce Kobe beef.

In 2003, in the largest agricultural-to-urban water transfer in United States history, San Diego County made a deal with the Imperial Valley to buy as much as two hundred thousand acre-feet a year. San Diego County has a growing metropolis, a population of three million, a substantial biotech industry, and virtually no natural water supply. By 2021, the transfer will account for a quarter of its water. The deal gives Imperial billions of dollars to spend on improving efficiency on its farms and in its irrigation infrastructure, which in some places is primitive.

The transfer, mutually beneficial and environmentally necessary, changes the Imperial Valley’s relationship to water, bringing it more in line with the realities of long-term drought in a state of thirty-nine million people. There is just one catch. Between the needs of the city and the farmers sits the Salton Sea, which conservation will destroy. “The sea is the linchpin between Colorado River water and urban Southern California,” Michael Cohen, a senior research associate at the Pacific Institute, a water-policy think tank, says. Without the inflows, the sea, already shrinking, will recede dramatically, exposing miles of lake bed loaded with a hundred years’ worth of contaminants. Much of the wildlife will disappear—poisoned, starved, or driven off. The consequences for people around the region could be dire, too. Before irrigation, the valley was plagued by violent dust storms. With the water gone, the lake bed could emit as much as a hundred tons of fine, caustic dust a day, leading to respiratory illness in the healthy and representing an acute hazard for people with compromised immune systems. No one knows how far that dust can travel on the wind. Mary Nichols, the state’s top air-quality official, says, “The nightmare scenario is the pictures we’ve all seen of the Dust Bowl that contributed to the formation of California in the first place.”

Last year, when Axel Rodriguez was four, he started coughing, a weird cough that sounded like a drum, deep and percussive, and scratchy, as though something inside his chest were trying to claw its way out. The cough would go away for a few days, only to come back stronger.

Axel’s mother, Michelle Valdez, is twenty-four, with straight, dark waist-length hair and, behind studious glasses, eyes made up like Cleopatra. She told me recently that the problem had started in August, when the family moved into a new house, a pale-yellow stucco rental in Calexico, about thirty miles south of the Salton Sea. “The houses in this area catch a lot of dirt,” she said—from the cars on the heavily trafficked road nearby, from the grass that the landlord insists on mowing, from neighboring Mexicali, the polluted city of a million just across the Mexican border, and, most of all, she said, from the farm fields throughout the valley. “We are in a hole here,” she said. “All the nasty stuff just sits in it.”

In September, the cough came and didn’t let up for two weeks. “Morning, afternoon, evening, it was cough, cough, cough,” Valdez said. Axel missed school, and his throat got so swollen that he could barely eat. He became a regular at the emergency room. Valdez and her husband, Antonio Marron, plied Axel with cough syrups, drops, Claritin—they’d been told he had allergies—and when those didn’t work they contemplated taking him to Mexicali for an herbal cure. “I was very desperate,” Valdez said. The medicines were also putting pressure on their finances. At the time, Marron was making about two hundred dollars a week working at Best Buy; Valdez stayed home, taking care of Axel and his sister, Ana, who is three.

One windy, cold morning in September, Axel told his mother that his chest hurt and he couldn’t breathe. Marron covered Axel’s face with a blanket and took him to the emergency room again. His lungs were swollen and full of mucus. This time, Marron was told what the family had already begun to suspect: Axel had asthma. At the hospital that day, they met a nurse, Aide Fulton, who runs the Imperial Valley Child Asthma Program. She began to educate them about how to manage a chronic condition in an environment seemingly designed to aggravate it.