On October 28, 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.

“The trend now is to move water from agricultural to urban areas because that’s where the growing demand is,” says  Michael Cohen, a senior research associate at the The Pacific Institute, an environmental research organization. “But doing that has huge environmental consequences that now manifest at the Salton Sea.”  By the early 2000s, it had become clear that the lake was headed for disaster: The agricultural runoff that sustained the lake contained not only fertilizer and pesticides, but high quantities of salt. Over the years, the salinity rose enough to kill off the lake’s fish species, even salt-water fish.  The only survivor was the hardy tilapia, an African freshwater fish that was originally introduced into the canal system to control algae growth. The water-quality concerns and massive fish die-offs further damaged the Salton Sea’s reputation and discouraged tourism or investment.

In 2002, a small amount of hope arrived for those hoping to save the lake from its seemingly inevitable death. The utility company Imperial Irrigation District made a deal to divert billions of gallons of water every year to San Diego County—the largest farm-to-city water transfer in U.S. history—on the condition that the state of California would assume future responsibility for the Salton Sea. For its part, the Imperial Irrigation District agreed to continue for a period of time to supply mitigation water from fallowed farmland to offset evaporation and shrinkage of the Salton Sea.

“Our lifeblood is agriculture,” says Robert Schettler, an Imperial Irrigation District spokesperson. “But we agreed to fallow agricultural land for 15 years to give the state enough time to figure out what to do.”

But the 15 years are nearly over, and thus far, the state has failed to act. At the end of 2017, the flow of water into the lake will be greatly reduced, causing salinity to spike; eventually, even the hardy tilapia will die off, the birds that feed on them will either migrate or die off themselves, and the dust will only get worse.

For a vivid example of the health hazards and environmental costs associated with a dry lake bed, one need only look north of the Salton Sea to Owens Lake. West of the Sierra Mountain Range, this lake was drained in the 1920s to meet the water needs of a growing Los Angeles. The dry lake bed is now the biggest manmade source of hazardous dust in the United States; Los Angeles has spent more than $1.2 billion dollars trying to suppress the dust, pouring 30 billion gallons of water onto the lake bed each year, but air-quality problems remain. Hazardous dust levels around the lake bed are 10 times the acceptable standard.

Compared to the Salton Sea, Owens Lake is in a much cooler, less arid climate, is much smaller (the treated area covers 27 square miles), and sits in a much less populous region—meaning that the Salton Sea, if nobody intervenes, will be a much bigger problem.

But nearly all the solutions that have been proposed have one thing in common: an unrealistically high price tag. The state issued a $9 billion plan in 2007, for example, that failed to gain any traction—possibly because Imperial County, one of the poorest counties in California, has relatively little political muscle. “If the Salton Sea was next to Sacramento, San Francisco, or Los Angeles, the problems would have been fixed a long time ago,” Cohen says.

The long-term price of inaction, though, is staggering. It’s challenging to put a dollar amount on the loss of a vital bird sanctuary or the loss of a recreational lake, but the human-health costs of a dead, shrunken Salton Sea are enormous. Some voice concern that a severe wind event might spread the lake’s hazardous dust towards the heavily populated coastal cities or even as far as Arizona, affecting millions. Windblown dust and salt could also take a heavy toll on the area’s agribusinesses, financially harming even more people.

One more recent idea that seems to be gaining popularity is a canal or pipeline that would link the Sea of Cortez in Mexico to the Salton Sea, pumping in water to re-cover the exposed playa. But some, including Cohen, are skeptical of the idea, citing the great distance a pipeline would need to cross (over 160 miles), the need for an agreement with Mexico, and the high price tag. It would also take years to  to negotiate, fund, and build such an ambitious project—and perhaps the biggest challenge in saving the Salton Sea is that time is no longer an available luxury. “The Salton Sea is in bad shape now, but in 2018 it’s going to get much worse, very rapidly,” Cohen says.

In August, the Imperial Irrigation District, in conjunction with Imperial County, released a new proposal called “The Salton Sea Restoration and Renewable Energy Initiative.” The proposal envisions a much smaller lake, around a third of its current size, surrounded by shallow ponds that would support bird life and suppress dust. If approved, proponents of the plan argue, it could be enacted relatively quickly, and at a comparably low cost.

But the proposal, which calls for geothermal-power development to help fund the ongoing restoration of the Salton Sea, would also signal the end of the lake as it’s been known for the past several decades. There’s currently one geothermal power plant on the lake, but its energy is sold to Arizona; if produced for California residents, geothermal energy could help address the state’s long-term goals of greatly increasing renewable-energy resources. The resulting Salton Sea would be an entirely different entity, with little or no resemblance to its past life as a fishing and tourist mecca.

“There were a lot of people who wanted to see the Salton Sea returned to the way it was in the 1950s,” Wilcox says, but “that’s just not possible. You can’t have that kind of lake [anymore].”

“We were all waiting for that perfect solution,” he adds, “and most of us have realized there isn’t a perfect solution.” And in the meantime, the clock is ticking.