Water loss in Mono Lake
Mono Lake, located in east-central California, is a unique saline lake that has experienced significant water loss due to the diversion of stream water for municipal use by the city of Los Angeles. This diversion, which began in 1941, has led to a drastic reduction in the lake's water levels—by over 15 meters (49 feet)—and an increase in salinity, which now contains approximately three times the dissolved salts of seawater. The lake is primarily fed by underground water and streams from the Sierra Nevada, with evaporation being the main method of water loss, as it has no natural outlet.
The ecological impact of water loss has been profound, affecting the lake's delicate ecosystem that supports limited plant and animal life. While fish cannot survive in the high salinity, species like brine shrimp and alkali flies thrive, and certain birds, such as California gulls and eared grebes, rely on these organisms for food. Environmental concerns have risen over the years, prompting lawsuits and advocacy for more sustainable water practices. In response to these pressures, Los Angeles has begun to reduce its water extraction from Mono Lake, with hopes of restoring its natural levels and ecology. The ongoing efforts signify a broader recognition of the need to balance urban water demands with environmental stewardship.
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Water loss in Mono Lake
IDENTIFICATION: Natural saline lake located in east-central California
The diversion of stream water from Mono Lake for use by the city of Los Angeles led to lowered water levels and higher-than-normal salinity in the lake, which had serious impacts on the lake’s delicate ecosystem.
Mono Lake, which covers about 150 square kilometers (58 square miles), receives most of its water from underground water flow and from streams that drain from the Sierra Nevada to the west. The lake has no outlet, so evaporation is the main natural cause of water loss. Since 1941, the city of Los Angeles has diverted water from the streams that drain into Mono Lake into the Los Angeles Aqueduct to supply the city with water. This loss of stream water into the lake resulted in a drop in the lake’s water level of more than 15 meters (49 feet), with a consequent increase in dissolved constituents in the lake.
By the early twenty-first century, Mono Lake’s water contained about three times the of dissolved salts found in seawater. The main kinds of dissolved ions (charged particles) found in the lake are sodium, chloride, and carbonate-bicarbonate. Lesser amounts of potassium, magnesium, and sulfate ions are also present. In addition, the waters have a very low hydrogen concentration (low acidity) and high hydroxide ion concentration compared with most natural waters. Nitrate, phosphate, and ammonium ion concentrations are also fairly high compared with most natural waters, especially in the lower portions of the lake. These ions help to stimulate the growth of in the lake waters.
The fairly high concentrations of calcium and carbonate-bicarbonate ions in some places in Mono Lake have caused chemical precipitation of tufa towers (composed of calcium carbonate) underwater, often helped by the action of algae. As the lake levels have dropped, the tufa towers have become exposed around the edges of the lake in certain places. The towers provide nesting places for some owls, falcons, and small mammals.
Plants and Animals
Mono Lake is too salty for fish and most water birds. In the spring, however, the lake explodes with millions of tons of and other small plants. Two larger organisms feed on the algae: brine shrimp and small alkali flies. Brine shrimp are small crustaceans that are often red. Each is only a little more than 1 centimeter (0.4 inch) long, with small appendages that they use to move algae into their mouths. They are found in Mono Lake, mostly in the upper, oxygen-rich waters, only from spring to fall; it has been estimated that some seven trillion shrimp may inhabit the lake at their seasonal peak. Alkali flies occur in swarms along the shoreline of the lake. They feed on the algae and lay eggs in algal mats underwater.
A few species of birds have adapted to being able to use Mono Lake at least during some parts of the year, especially when there are large quantities of brine shrimp and alkali flies to eat. The California gull is one such bird; these gulls are abundant in the summer, when they form nests on some of the small islands in the lake. The gulls migrate toward the ocean during the winter. The eared grebe is another bird that lives in the lake in the summer and fall, consuming vast amounts of brine shrimp before flying south in the winter to the Gulf of California. The red-necked phalarope and Wilson’s phalarope stop over at Mono Lake, where they consume large quantities of alkali flies, before flying more than 4,800 kilometers (about 3,000 miles) south in the winter to places in South America. The American avocet, a long-legged wading bird, stops at the lake in the spring when flying to the north and in the fall when flying to the south. Many kinds of ducks also stop by the lake, although the waters are too salty for them to spend much time there. Before Los Angeles diverted the freshwater streams draining into Mono Lake, many more kinds and numbers of ducks used to stop at nearby streams and visit the less salty waters in the lake near the streams.
Environmental Problems
The diversion of stream flow from Mono Lake to the Los Angeles Aqueduct that began in the 1940s resulted over time in a large drop in the average volume of water in the lake and, thus, lowered the lake level. The of the waters eventually doubled in concentration, reducing the production of algae and thus the populations of brine shrimp that fed on the algae. The lake’s recreational uses were also affected, as boat docks and beaches were left without water near them as the water level dropped. Up to five-sixths of the average flow of stream water that had originally gone to Mono Lake was being diverted to Los Angeles, and in years with low rainfall, some streams simply dried up. The fish populations, vegetation, and that depended on these streams were severely damaged.
Beginning in 1979, environmentalists brought lawsuits intended to force the city of Los Angeles to stop diverting water from Mono Lake. After many court decisions and appeals, in the mid-1990s, Los Angeles was required to reduce its diversion of Mono Lake waters so that the original level and salinity of the lake could eventually be restored.
Despite these measures, water levels in Mono Lake continued to suffer from stream diversions. During the 2020s, the Mono Lake Committee requested that the State Water Resources Control Board issue an emergency pause on all water diversions from the lake. Environmentalists also argued that rather than relying on stream diversions, the city of Los Angeles should invest in the development of more sustainable water sources or restrict its water usage. Because of their pleas, in 2024, Los Angeles agreed to take less water from the lake, 4,500 acre-feet instead of 16,000 acre-feet. Environmentalists believe this will significantly add to a natural rise in the lake's water level that occurred during this year.
Bibliography
Bland, Alastair. "L.A. Has Taken Water from Iconic Mono Lake for 82 Years. Will California Stop It?" Calm Matters, 30 May 2023, calmatters.org/environment/water/2023/05/mono-lake-water-diversion/. Accessed 18 July 2024.
Carl, David, and Don Banta. Mono Lake Basin, California. Mount Pleasant, S.C.: Arcadia, 2008.
Flaherty, Dennis, and Mark A. Schlenz. Mono Lake: Mirror of Imagination. Santa Barbara, Calif.: Companion Press, 2007.
Hart, John. Storm over Mono: The Mono Lake Battle and the California Water Future. Berkeley: University of California Press, 1996.
James, Ian. "As Los Angeles Plans to Take Less Water, Environmentalists Celebrate a Win for Mono Lake." The Los Angeles Times, 2 June 2024, www.latimes.com/environment/story/2024-06-02/mono-lake-los-angeles-water-decision. Accessed 19 June 2024.
Mono Basin Ecosystem Study Committee. The Mono Basin Ecosystem. Washington, D.C.: National Academy Press, 1987.
"Mono Lake's Exciting Rise May Well Disappear." Mono Lake Committee, 30 May 2023, www.monolake.org/today/mono-lakes-exciting-rise-may-well-disappear/. Accessed 18 July 2024.