BRAWLEY, Calif. — The drought crisis on the Colorado River looms large in California’s Imperial Valley, which produces much of the nation’s lettuce, broccoli and other crops, and now faces water cuts. But those cuts will also be bad news for the environmental and ecological disaster unfolding just to the north, at the shallow, shimmering and long-suffering Salton Sea.

“There’s going to be collateral damage everywhere,” said Frank Ruiz, a program director with California Audubon.

To irrigate their fields, the valley’s farmers rely completely on Colorado River water, which arrives by an 80-mile-long canal. And the Salton Sea, the state’s largest lake, relies on water draining from those fields to stay full.

But it’s been shrinking for decades, killing off fish species that attract migratory birds and exposing lake bed that generates dust that is harmful to human health. As the sea has receded, it’s also left abandoned houses, shuttered resorts and landlocked marinas that, in the mid-20th century, had transformed the area into a fishing and water-sports playground for Southern Californians.

Now, with cuts in water use coming after two decades of drought that have left the Colorado’s reservoirs at dangerously low levels, the sea will shrink even faster. “Less water coming to the farmers, less water coming into the Salton Sea,” Mr. Ruiz said. “That’s just the pure math.”

Audubon has a project to protect and improve several hundred acres of wetlands on the sea’s eastern shore to attract birds on what is an important migratory flyway. But the stakes are even higher a dozen miles to the south, where for more than $200 million the state is creating new wetlands, 4,100 acres of wildlife habitat that are being carved out of dried-up lake bed.

There is a plan to complete other, similar projects this decade, to restore some sense of environmental normalcy to the sea — if the state can keep up as the water recedes.

“We know we’re going to need to accelerate implementing these projects,” said Lisa Lien-Mager, a spokeswoman for the California Natural Resources Agency, which oversees the state’s Salton Sea activities.

The sea has been a slow-moving train wreck for years. It was created in 1905 when an engineer tried to divert some of the Colorado’s flow into a canal. But the diversion was poorly designed and easily overwhelmed, and soon the entire volume of the Colorado began pouring into what was then the Salton Sink, more than 200 feet below sea level. The water continued flowing for nearly two years.

Over previous centuries, the sea had formed here occasionally, a result of natural changes in the Colorado River. But with little rainfall and few other natural sources of water, it always dried up. This time, though, as settlers arrived and farming began, agricultural drainage water replenished what was lost to evaporation. Which means as long as there’s cropland and irrigation in the nearby Imperial Valley, the lake will likely remain.

Today the Salton Sea covers some 350 square miles, but keeping it full has been a losing battle in recent decades, as Imperial Valley farmers undertook water conservation efforts after they agreed to transfer some of their water to San Diego and other cities. The efforts, which saved about 500,000 acre-feet a year, reduced inflows into the sea. (An acre-foot is the amount of water used by two to three households a year.)

Other ways to stem the sea’s decline have been proposed, including piping in seawater from the Sea of Cortez in Mexico, an idea that a state-appointed expert panel recently rejected as too costly and impractical.

Now, to help stave off disaster on the Colorado, growers here are expected to lose another 250,000 acre-feet of water a year.

As the sea has shrunk it’s become so salty — it’s currently nearly twice as salty as seawater — that only a handful of fish species, including tilapia and the endangered desert pupfish, remain. With fewer fish, bird populations along what is an important migratory flyway have declined.

Human health has been affected, too. The retreating water has exposed huge expanses of lake bed, and with wind stirring up dust from them, air quality in the Imperial Valley is among the worst in the state. That’s led to a high incidence of childhood asthma and other respiratory illnesses among the valley’s 180,000 residents.

The need to cut Colorado River water use is a contentious issue among the seven states that use it. California, which has the largest allotment, is currently at loggerheads with the other states over how to reduce consumption by up to 40 percent of the river’s annual flow, as demanded by the federal government. A January deadline for a deal passed with no resolution, and the government may be forced to step in and make cuts.

The valley’s water distributor, the Imperial Irrigation District, itself is the biggest user of Colorado water, with rights to about one-fourth of the overall annual allotment of all seven states. California officials have offered some cuts, most of which would come from the district. A reduction of 250,000 acre-feet would equal about 8 percent of the district’s allotment.

Scott Emanuelli, the president of the Imperial Valley Farm Bureau, said growers have conserved water in the past and were willing to do more now if needed. “We’re accustomed to bearing the burden,” Mr. Emanuelli said. Growers would be paid for conserving water, with money likely to come from the Inflation Reduction Act.

The other Colorado River states have complained that California is not offering to sacrifice enough. But for Tina Shields, the manager of the irrigation district’s water department, an 8 percent reduction is significant.

Ms. Shields said the cuts might be met by improving irrigation efficiency, which some of the valley’s farmers have already done, or by reducing the number of cuttings of hay and other forage crops. But the reductions are so large that some fallowing will probably be needed.

“And that’s a bitter-pill word for us,” she said. Idled farmland means less work and less spending on supplies and equipment, effects that would ripple through the economy in one of the poorer parts of California, where about one in six people already live in poverty. “It’s not good for our community,” Ms. Shields said.

But faster shrinking of the Salton Sea isn’t good either, she said.

“It’s like we’re between a rock and a hard place,” Ms. Shields said. “We do a really good thing by becoming more efficient. And then it’s like, ‘Oh, by the way, now you have this negative impact from the Salton Sea, that your kids are potentially going to get sick from some really crummy air quality.’”

Mr. Ruiz of California Audubon said he was not concerned about the farmers. “They’re going to get paid for fallowing their lands, or retiring their lands or maybe just reducing the number of crops,” he said. But like Ms. Shields, he was worried about the health effects of a more rapidly shrinking sea.

In addition to protecting wildlife habitat, the Audubon project aims to deal with that in a small way for now. The site, about a mile’s hike from the half-abandoned, graffiti-riddled town of Bombay Beach, across an expanse of barnacle shells and fish bones that crunch under foot, consists of wetlands that have appeared as the lake has receded.

Fed by spring water — unusual for the Salton Sea — these areas are now home to small shorebirds who flit about pools of water amid grasses and invasive tamarisk. But without efforts to stabilize them the wetlands could disappear, said Camila Bautista, a program coordinator with Audubon.

“We want to work with the existing wetland and enhance the features there to allow the wetland pools to persist,” she said. The plan, which is still in its design stages, would also reroute some water to adjacent areas of exposed lake bed to further control dust.

To the south, at the state project, bulldozers, graders and trucks are creating new wetlands, rearranging the dry lake bed into habitat for fish, birds and other wildlife. When completed later this year, the project will consist of a network of ponds with nesting and “loafing” islands for birds, fed by pumps and a diversion dam.

The idea, said Vivien Maisonneuve, program manager with the state Department of Water Resources, is to replicate what is successful in nature.

There already appear to be some signs of success, with anecdotal reports of increased numbers of pelicans and other birds, including, recently, a bald eagle. “So it’s already coming back,” Mr. Maisonneuve said.

The water will come from the Salton Sea and from the New River, the main route for drainage water, with the two sources being mixed to control salinity and naturally occurring selenium, which can accumulate in the food chain and harm wildlife. By inundating nearly seven square miles of lake bed, the project will also eliminate a source of dust.

But just beyond the berms that will keep water in the new ponds, the Salton Sea is still shrinking, exposing more lake bottom.

While the state’s plans call for improvements, some as elaborate as the current project, on 30,000 acres of dry lake bed by 2028, estimates suggest that about 55,000 additional acres will be exposed by the middle of the century. And that total likely will be reached even faster now, with the new cuts in the Colorado River supply.

The current project offers a constant reminder of what’s to come. The pump station taking Salton Sea water for the new ponds and wetlands is fed by a trench that extends three miles into the lake, in anticipation of an ever-drier future. “Even as the sea is receding, water will be able to reach the pump station to keep the project working in the future,” Mr. Maisonneuve said.