As this drought-stricken body of salt water recedes, the repercussions mount: Its exposed alkaline flats are giving rise to dust storms. A haven for endangered migrating birds has become more vulnerable to predators. And Los Angeles' ability to divert snowmelt from the region — which it has done for seven decades — could be cut off.
In recent months, the Department of Water and Power has reduced its take from Mono's tributaries by more than two-thirds. Still, the 1-million-year-old lake is within two feet of the level that state officials say threatens the alpine ecosystem at the base of the eastern Sierra Nevada.
FOR THE RECORD:
Mono Lake: In the June 25 Section A, a graphic with an article on the effects of the drought on Mono Lake showed the scale as water level in feet. The scale should be water level in feet of elevation.
Unless the region gets a significant amount of rain by the next official water level reading in April, Mono may fall to 6,377 feet in elevation, triggering a halt to any diversions. The California State Water Resources Control Board established the limit in 1994 to resolve a dispute between environmentalists and the city 350 miles south.
Of particular concern is further exposure of a land bridge that coyotes could cross to access the second-largest California gull colony in the state. That passageway to Negit Island and nearby islets is surfacing, leaving the eggs and chicks vulnerable.
"I'll be terrified if the lake level drops another few feet," said Kristie Nelson, a biologist who has been conducting research on Mono Lake's gull population since 2004. "In years past, coyotes have been known to swim across 200 yards of water to get to the gull eggs."
Famous for its towering, craggy tufa formations, the high desert lake east of Yosemite National Park is the remnant of a vast inland sea, where fresh alpine runoff cascading from Sierra slopes combines with salty water that is home to brine shrimp.
The controversy over the city's diversions of water from Mono's feeder streams is one of California's longest-running environmental battles.
In April, the DWP reduced its annual water exports from 16,000 acre-feet to 4,500 acre-feet, when gauges recorded the surface level at 6,379 feet in elevation. An acre-foot of water is enough to supply two households for a year.
In a separate effort to conserve meager eastern Sierra snow runoff, the DWP dammed the Los Angeles Aqueduct this year. That closure will remain in place until November so the DWP can fulfill obligations such as dust mitigation on Owens Lake, which dried up after the city water agency opened the aqueduct in 1913.
Usually, the aqueduct supplies Los Angeles with a third of its water.
"If the lake level falls more than two more feet, we'll be in the hands of the weather gods," said Geoffrey McQuilkin, executive director of the Mono Lake Committee, a nonprofit group focused on protecting the ecosystem.
"There's no contingency plan on the shelf for record drought."
The committee has started weighing emergency proposals, including construction of chain-link or electric fences between the mainland and offshore nesting sites. Video cameras were recently installed "to see if coyotes are testing the boundaries," McQuilkin said.
In the meantime, the shoreline is steadily falling back, creating a "bathtub ring" of dusty lake bottom. Warmer temperatures, increased turbidity and reduced flows in the tributaries — Lee Vining Creek, Walker Creek, Parker Creek and Rush Creek — threaten trout populations and riparian vegetation that is home to migrating birds such as yellow warblers and lazuli buntings.
With evaporation outpacing inflows from those streams, a sheet of water less than 4 feet deep and few hundred yards wide is all that protects tens of thousands of breeding gulls from predatory coyotes.
The situation is reminiscent of 1978, when, due to unrestricted city diversions, the lake level had dropped so low that the land bridge to Negit Island was fully exposed. The California National Guard, with the support of the Audubon Society, tried to blow it up with dynamite, but the muck exploded sky high and then simply fell back into place.
A year later, a chain-link fence was installed on the island. But as the water evaporated, coyotes padded around the ends of the fence and devoured nestlings.
In an escalation of firepower, the U.S. Forest Service in 1990 strung 1,100 yards of low-voltage wire across a portion of Mono's north shore, in hopes a jolt on the snout would discourage coyotes from crossing shallow water to raid the rookery.
The electronic barrier didn't work, Nelson said, "because the system rapidly degraded in the corrosive alkaline foam and water blowing off the lake."
Standing beside a water level gauge separated from the lake by a hundred of yards of dry land, Nelson said: "We have to take a hard look at all options. These birds are in serious danger."
Los Angeles has diverted a total of 4.28 million acre-feet of water from the Mono Basin since 1941.
Formal protests began with a lawsuit that residents and environmental groups filed in Mono County Superior Court in 1979 against the DWP. The suit alleged violations of public trust and the creation of a public and private nuisance by exposing 14,700 acres of former lake bed.
In 1983, the U.S. Supreme Court let stand a ruling that environmentalists had the right to challenge the amount of water Los Angeles was exporting from the tributaries. A decade later, the state water board ordered minimum flows restored for the diverted streams and set the minimum water level for Mono Lake.
So far, the 6,377 mark has never been reached.
Now "after two decades of protections," McQuilkin said, "we're facing some of the same issues we were concerned about in the 1970s."
"Only this time," he added, "it's not Los Angeles' fault."