Environmentalists say there is some urgency to the problem. A recent report by the Pacific Institute, a nonprofit based in Oakland, predicts that in 15 years the water volume will decrease by 60 percent, 100 square miles of lake bed will be exposed and the water will get three times as salty. The average depth of the receding sea is now less than 30 feet.

The big fish, mostly tilapia now, could disappear. If so, migrating birds, like the brown pelicans on the shore here, will have little to eat. The exposed sand and dust, blown by desert winds, will contribute to dust clouds, making attainment of federal air quality standards impossible. Over 30 years, the cost of inaction, the Pacific Institute report argues, will be $29 billion to $70 billion.

In some ways, Salton’s fate is like that of other disappearing saline lakes, such as the almost-vanished Aral Sea in Central Asia and Lake Urmia in Iran: They are slowly getting saltier and disappearing because people have purloined the water that flows into them.

The Salton Sea’s increasing brininess and oxygen deprivation caused by abundant algae are fatal to fish, whose remains sometimes line the beaches. And perhaps because this organic matter is fermenting in a place without oxygen, it sometimes emits a rotten-egg smell that can be blown as far as Los Angeles, 150 miles away.