Owens Lake, California

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Figure 1. Seasonally measured evaporation from the three dominant types of surface sediment in Owens Lake, California. Squares in the inset map show monitored sites (after Tyler et al., 1997; Warren, 2016)

Desiccation of a saline lake

Owens Lake is a mostly dry lake sump in Owens Valley on the eastern side of the Sierra Nevada in Inyo County, California. It lies some 8.0 km south of Lone Pine, California. Unlike most playa lakes in the Basin and Range Province which have been dry for thousands of years, Owens held significant water until 1913. Then most of the flow in the Owens River was diverted into the Los Angeles Aqueduct, so that by 1926 Owens Lake had desiccated Today, some of the river flow has been restored, and the lake now contains a little water. Nevertheless, as of 2013, Owens Lake wass the largest single source of dust pollution in the United States.

Before the diversion of the Owens River, Owens Lake was up 19 km long and 13 k) wide, covering an area of up to 280 sq. km. In the last few hundred years, the lake had a variable depth of 7.0 to 15.2 m and sometimes overflowed to the south into the Mojave Desert. In 1905, the lake water was declared "excessively saline," and so the inflow deemed suitable for diversion.

In the late Pleistocene, some 11-12,000 years ago, Owens Lake was almost twice as large, covering some 520 sq. km, with a depth of up to 61 m. Increased inflow from the Owens River, from melting glaciers the post-Ice Age Sierra Nevada, caused Owens Lake to overflow south through Rose Valley into another playa, China Lake. After the glaciers melted, the lake waters receded.

Changing lake levels

 Human exploitation of the inflow was occurring, and the lake level was dropping, even before the Los Angeles Aqueduct was built. Owens Valley farmers were diverting most of the Owens River's tributaries' flow, causing the lake level to drop slightly each year. Starting in 1913, the river and streams that fed Owens Lake were diverted by Los Angeles Department of Water and Power (LADWP) into the Los Angeles Aqueduct, and the lake level started to drop more rapidly quickly.

The lake bed is currently a large saline mudflat, with surface sediments made of a mixture of clay, sand, and a variety of saline minerals including halite, burkeite, mirabilite, thenardite, and trona. In wet years, these minerals form a chemical soup in the small brine pond occupying the lowest part the dry lake sump. When conditions are right, bright pink halophilic archaea spread across the brine-covered parts of the lake bed. Also, on scorching summer days when ground temperatures can exceed 66 °C), water is driven out of hydrated saline minerals facilitating a muddy brine. More commonly, periodic winds stir up noxious alkali dust storms on the dry lake floor that carry away as much as four million tons (3.6 million tons) of saline dust from lakebed each year. This dust can cause respiratory problems in nearby residents. The dust can entrain carcinogens, such as cadmium, nickel and arsenic.

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Dust blowing of the dry surface of the desiccated Owens Lake


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Reflooded portion of Owens lake at sunset

Mitigating the effects of desiccation

As part of an air-quality mitigation settlement, LADWP is currently shallow flooding 70 sq. km of the dry salt pan to try to help minimise alkali dust storms and other adverse health effects. There is also about 3.5 square miles (9.1 km2) of managed vegetation being used as a dust control measure. The vegetation consists of saltgrass, which is a native perennial grass highly tolerant of the salt and boron levels in the lake sediments. Gravel covers are also in use.

Before its desiccation, the once-blue perennial saline lake was an important feeding and resting stop for millions of waterfowl each year. During a visit to Owens Lake in 1917, Joseph Grinnell of the Museum of Vertebrate Zoology Berkeley reported;

"Great numbers of water birds are in sight along the lakeshore--avocets, phalaropes, ducks. Large flocks of shorebirds in flight over the water in the distance, wheeling about show in mass, now silvery, now dark, against the grey-blue of the water. There must be literally thousands of birds within sight of this one spot."

Owens Lake is still recognised as an Important Bird Area in California by the National Audubon Society, and as part of current dust mitigation efforts, shallow flooding of the lakebed creates both superficial and deeper (0.9 m) avian habitats on the lakebed. Flooding is helping to buoy the lake's ecosystem, causing hope in conservationists that an expanded shallow flooding program could do even more. But there are no serious plans to restore Owens Lake to anything resembling a conventional mesohaline lake. The ever-growing city of Los Angeles needs an ever-increasing supply of water.

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Migrating birds feeding on flooded flats at Owens Lake (2017)
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