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LA is getting less water from Mono Lake due to lower levels

With a third year of drought reducing streams cascading down the eastern Sierra Nevada, the level of Mono Lake has fallen so low it has resulted in a 72% reduction in the amount of water that Los Angeles may divert waterways from the area this year.

On April 1, the level of Mono Lake was just under 6,380 feet above sea level – about 1 inch below a threshold set in Department of Water and Power licenses. from Los Angeles to divert alpine runoff from streams that feed the lake east of Yosemite National Park.

The measure, taken at the start of a new year of runoff, triggered the requirement that the DWP reduce its annual water exports from 16,000 acre-feet, enough to supply 192,000 residents, to 4,500 acres. -feet, enough to serve 54,000 residents.

The last time Mono Lake fell below the same threshold was from 2015 to 2017, in the final years of California’s last severe drought. The level is measured by gauges along a crisp stretch of shoreline next to the town of Lee Vining.

The hypersaline desert lake, famous for its towering, craggy tuff formations, has been at the center of long-running disputes over the city’s water diversions from the lake’s waterways. The state Water Resources Control Board set limits on diversions in 1994 to resolve a fight between environmentalists and the city 350 miles to the south.

Since then, the DWP says its water diversions from the Mono basin have been reduced by 80% and that it has adopted an “environmentally-focused approach” to water exports that has included investment in restoration projects. The ministry says these projects have been successful in improving the ecological health of fish populations and riparian habitats that are vital for birds.

But conservationists remain concerned about the environmental effects of decades of water diversion, especially given the current extreme drought and worsening effects of global warming.

“Twenty-eight April 1sts have passed since the state water board’s decision,” said Geoffrey McQuilkin, executive director of the Mono Lake Committee, a nonprofit organization focused on protecting the ecosystem, ” yet Mono Lake remains chronically and artificially low.”

McQuilkin said Los Angeles has achieved remarkable success in conserving water and developing a sustainable water supply for its roughly 4 million ratepayers, but the city has yet to “repair the damage caused by decades of excessive water diversions at Mono Lake in the past”.

Adam Perez, DWP waterworks manager, said the department is fulfilling its obligations under its license agreement and is committed to protecting the environment and the health of Mono Lake and its waterways.

Department staff in the area include biologists, hydrologists and other specialists who study lake health, monitor flows and stream bottom sediments, and track fish populations and water sources. that support the birds. Perez said restoration projects in the Mono Basin have been successful in improving the health of streams, riparian vegetation and wildlife habitats.

“We’re trying to do our best to balance the needs of a big city and make sure we can balance the needs and restoration of Mono Lake as well,” Perez said.

After reductions in water deliveries during the last drought, Mono Lake levels rebounded with wet weather in 2017, then declined in the last three extremely dry years.

The city has put in place infrastructure to use water from several streams – Lee Vining Creek, Walker Creek, Parker Creek and Rush Creek – but is currently diverting water from two of them, Rush Creek and Lee Vining, while not using the other two, Perez mentioned.

In the last runoff year from April to March, the DWP exported 13,800 acre-feet from Mono Basin, less than the allowed 16,000 acre-feet. This amount will now decrease by two-thirds over the next 12 months.

In the nearly three decades since the state ordinance limited water diversions, the hydrology of the Eastern Sierra has become more extreme, with wet years wetter, dry years drier and longer droughts, which the DWP says has made efforts to raise lake levels more difficult. . In the past year of extreme heat and drought, the department says about 150,000 acre-feet of water evaporated from the lake’s surface.

In 1994, the state water board set a goal to restore Mono Lake to a level of 6,392 feet, about 12 feet above the current level, in order to protect the ecosystem, the quality of water and air quality. At that time, the DWP said officials had estimated, based on models, that the longest period to reach that level would be 38 years, or 2032.

“The long dry spells certainly impacted the ability of the lake to rise as expected in the 90s when they put these models together,” Perez said. And the department says updated models that include the effects of climate change suggest reaching that higher level could take years longer than expected.

Meanwhile, the shoreline of Mono Lake continues to recede, creating a “bathtub ring” at the dusty bottom of the lake. Warmer temperatures, increased turbidity and reduced stream flows threaten trout populations and riparian vegetation that supports migratory birds such as yellow warbler and lazuli sparrow.

With evaporation exceeding inflows from these streams, a sheet of water less than 4 feet deep and a few hundred meters wide is all that protects tens of thousands of breeding gulls from predatory coyotes.

“The relationship between Los Angeles and Mono Lake remains a work in progress,” McQuilkin said, “and the current drought isn’t helping.”

The DWP says cuts in water deliveries have left water in the Mono basin to support its environmental projects.

“The result of our work is significant,” the DWP said in an emailed statement. “Mono Lake and its tributaries now provide abundant resources for unique shore-nesting waterfowl, and a healthy environment for plants and fish to thrive.”

The department also plans to launch a $50 million project on the Lake Grant Reservoir spillway on Rush Creek, which it says will increase stream flow in wet years.

If the drought persists during this runoff year, Perez said, DWP will likely be allowed to export the same limited amount of water next year. If the lake continues to drop in coming years below a lower threshold of 6,377 feet, Perez said, “our exports would be essentially disabled from Mono Basin.”

Mono Basin water represents a small portion of the water that the DWP transports through the Los Angeles Aqueduct.

According to DWP figures, 48% of the city’s water between 2016 and 2020 came from the Eastern Sierra Aqueduct. The city purchased 41% of Southern California’s Metropolitan Water District, including 35% of the Bay Delta and 6% of the Colorado River. The remainder comprised 9% groundwater and 2% recycled water.

City officials have set goals to reduce Los Angeles’ reliance on imported water supplies and expand local supplies, including recycling more wastewater, capturing more stormwater and purifying contaminated groundwater so it can be pumped and used. But the DWP says local water supplies cannot fully replace imported water.

When the department faces cutbacks on the LA Aqueduct, the city typically secures water from the Colorado River Aqueduct and the State Water Project to supplement its supplies. But water agency managers expect to receive only 5% of their full allocations from the Bay Delta through the State Water Project this year, and the Colorado River is also experiencing severe shortages as reservoirs continue to dwindle. .

Governor Gavin Newsom called on Californians to voluntarily reduce their water use by 15%, and state officials urged residents to step up conservation efforts.

“Water allocations are extremely difficult for us at this point,” Perez said. “I think right now everyone across the state of California, across the West, is going to be looking at each other and finding ways to retain and do our part, because we’re in a tough spot.”

Los Angeles Times

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