Toxic Dust From a Dying California Lake

The shrinking Salton Sea is now a major source of air pollution—and no one seems to know how to stop it from getting worse

The smog-control agency for Los Angeles and the surrounding areas, the South Coast Air Quality Management District, issued an odor advisory for the intense rotten-egg stench that was permeating the air of southern California’s Coachella Valley. The source: The state’s largest lake, the 350-square-mile Salton Sea, was burping up hydrogen sulfide, a gas created by the decaying organic matter trapped beneath the water. It was the Salton Sea’s fifth odor advisory for October alone; depending on winds, the hydrogen sulfide can be smelled as far as 130 miles away in Los Angeles.

But the smell is only one small part of a more serious public-health problem, one that has the potential to affect millions of people in southern California and beyond. The Salton Sea is shrinking, a phenomenon due partially to rapid evaporation—summer temperatures around the lake routinely top 110 degrees—and partially to the decrease in the agricultural runoff that was the lake’s primary water source.

The problem is exacerbated by both California’s ongoing drought and the shallowness of the lake: “Because the Salton Sea is so flat and shallow a vertical foot of drop can expose thousands of feet of horizontal playa,” or dry lake bed, explains Bruce Wilcox, an ecologist and the assistant secretary for Salton Sea policy, a recently created position within California’s Natural Resources Agency. As the playa is exposed, it dries quickly in the desert heat and sun; desert winds kick up the dust, creating a serious air-pollution problem. Imperial County, which houses the lake, currently has the highest asthma-hospitalization rates in the state. Because the lake has been used as an agricultural sump for more than a century, the dust also contains pesticides, and officials are concerned about the presence of potentially toxic heavy metals like arsenic.

But the window of time to do anything about it—and save the lake from ecological crisis—is rapidly closing.

Straddling Coachella and Imperial counties, the Salton Sea covers a desert region south of Palm Springs and north of the Mexican border. At 235 feet below sea level, the Salton Sea occupies what was once known as the Salton Sink, a forbidding sunken expanse of ancient dry lake bed with a black mud sub-surface that made crossings treacherous. The area was generally avoided until the end of the 19th century, when land developers realized that the area’s alluvial soil and the hot climate would, with irrigation from the nearby Colorado River, produce valuable farmland. A series of canals were built and water flowed in; soon, more than 10,000 farmers and farm workers relocated to the Salton Sink, now grandly rechristened the Imperial Valley, and quickly put 100,000 acres of land under cultivation.

In the spring of 1905, following extreme rains, the Colorado River flooded and blew out a weakly constructed irrigation canal. All efforts to seal the breach failed—for 18 months, the river continued to flood into the Salton Sink, filling it up with fresh water like an enormous shallow tub. The Southern Pacific Railroad, which had extensive rail interests in the area, jumped in and for two weeks stopped rail traffic in California in order to divert all rolling stock to Salton Sink. Two thousand workers dumped more than 3,000 specially constructed railroad cars full of boulders, wood, and dirt into the flooded canal. The scheme worked: The Colorado River once again resumed its former course into the Sea of Cortez. The lake left behind by the flooding wasn’t deep, but it was enormous, covering nearly a thousand square miles of land. The Salton Sea, as the lake was now called, was more or less left alone for the next several decades; runoff from the Imperial Valley’s huge farm areas offset much of the heavy annual evaporation rate and kept the lake viable.

In the 1950’s, with the rising popularity of the nearby desert resort of Palm Springs, developers once again saw opportunity in the Salton Sea. Towns like Salton City and Bombay Beach cropped up along its shoreline, along with resorts catering to tourists interested in water sports, fishing, and swimming. Meanwhile, fish that had been introduced to the lake were flourishing, and by the late 1950’s the Salton Sea was the most productive fishery in California. At its peak, the Salton Sea was drawing 1.5 million visitors annually, more than Yosemite.

Unfortunately, little thought and few resources were devoted to the management of this accidental lake. As a terminal lake, the Salton Sea lacks any outflow, and in the late 1970s a series of heavy tropical storms caused the water level to rapidly rise and flood its banks.  The surrounding towns and businesses were severely damaged, many beyond repair, and tourism began to shift away. In the 1990s the lake began to recede dramatically, stranding many of the remaining residences and businesses, as changing water management priorities diverted more water from agricultural areas to cities.

Source: The Atlantic

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