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. MORE