Los Angeles Aqueduct

IDENTIFICATION: System of canals, tunnels, and pipes built to divert water from the Owens River to Los Angeles

DATE: Completed on November 5, 1913

The Los Angeles Aqueduct was constructed to meet the growing demand for water in the city of Los Angeles, but the diversion of water from the Owens River led to the drying of the Owens River Valley and the subsequent collapse of that region’s agricultural industry.

The Los Angeles Aqueduct extends 378 kilometers (235 miles) from the Owens River a few miles north of Independence, California, to San Fernando, California, on the north side of Los Angeles. Begun in 1908 and completed in 1913, it is a complex system of unlined, lined, and lined and covered canals, tunnels, and steel pipes. For seventy-three years the entire flow of the Owens River at the aqueduct intake point, an average of about 984 million liters (260 million gallons) per day, was diverted from the Owens Valley to Los Angeles. Beginning in 1986, a portion of the original flow was restored to the Owens River below the intake point. The aqueduct was extended north to the Mono Lake basin in 1940, and a parallel aqueduct was completed in 1970.

In 1900 the of Los Angeles was about 200,000 and was rapidly increasing. The city’s water supply came from the Los Angeles River and a few wells and local springs. A substantial supply of water was required for the city to continue to grow, and there was no local source. To solve the problem, Fred Eaton, an engineer and former mayor of Los Angeles, conceived the Los Angeles Aqueduct and discussed his idea with William Mulholland, superintendent of the Los Angeles Department of Water. Mulholland spent forty days surveying the proposed aqueduct route and discussed the proposal with the Los Angeles Board of Water Commissioners. All this was done in secret to avoid a burst of land speculation. Eaton had already obtained options to buy most of the private land along the aqueduct route and later agreed to sell the options to Los Angeles at cost.

One obstacle remained. The US Reclamation Service (which was created in 1902 and renamed the Bureau of Reclamation in 1923) was in the process of planning a major project in the Owens Valley and had withdrawn the public lands in the area from claim. Part of the aqueduct route passed through these public lands. The residents of the valley were enthusiastically in favor of the irrigation project.

Plans for the aqueduct were made public, and a committee from the Los Angeles Chamber of Commerce met with President Theodore Roosevelt. To the disappointment of the Owens Valley residents, President Roosevelt reached the conclusion that the Owens River water would be much more beneficial to Los Angeles than to Owens Valley, and in 1906, the US Congress granted the necessary right-of-way for the aqueduct. To ensure its right to the Owens River water and increase the available supply, the city of Los Angeles began buying the irrigated ranches and farms above the aqueduct intake in addition to properties below the intake that were now useless for lack of water. It was this maneuver, rather than the building of the aqueduct itself, that angered Owens Valley residents.

The Owens River Valley lies between the Sierra Nevada mountain range to the west and the White Mountains and Inyo range to the east. It is about 16 kilometers (10 miles) wide and 160 kilometers (100 miles) long. In its pristine state, the valley was a desert. The Owens River, flowing south from the Sierra Nevada, supported a fringe of willows and other riverside vegetation; the rest of the valley was thinly covered with cactus, chaparral, and sagebrush. The river ended at Owens Lake, an alkaline lake with no outlet. Because of evaporation over many thousands of years, the lake water was highly mineralized, primarily with sodium bicarbonate, but also with sulfates, chlorides, and other salts. The upper end of the lake was a freshwater marsh, which provided good for waterfowl, as did the river north of the lake. The river, its fringe of vegetation undoubtedly home for many native birds, was on a major migratory for several species of birds. Irrigation ditches serving farms, ranches, and orchards extended as far as 8 kilometers (5 miles) from the river. Carp, an exotic fish imported from Europe, swam in the irrigation ditches.

On completion of the Los Angeles Aqueduct in November 1913, the lower 85 kilometers (53 miles) of the Owens River channel became dry; partial flow was not restored until 1986. The narrow fringe of riverside vegetation died, the marshes at the head of Owens Lake dried, and, eventually, the lake itself dried. Windstorms crossing the dry lake bed carried irritating alkali dust through the valley and often far beyond. The irrigated farms and ranches almost entirely disappeared, and Los Angeles, which owned most of the valley, allowed it to return to desert. The economy of the valley changed from one based on agriculture to one based on tourism and outdoor recreation. In purely economic terms, the income from tourism and outdoor recreation has vastly exceeded what might have been expected from an expansion of irrigation-based agriculture in the region.

By 1970, Los Angeles was using large quantities of well water to supplement aqueduct flow, lowering levels and drying local springs. In addition, the water level at Mono Lake was declining, threatening island breeding grounds of California gulls by creating land bridges that coyotes could cross.

If the aqueduct had not been built, the Reclamation Service probably would have constructed massive irrigation systems that might have been much more damaging to the of Owens Valley. Indeed, a Sierra Club spokesman once said, “We recognize that Los Angeles is probably the savior of the valley. Our goal is to save the valley as it is now.”

Environmental Impact and Climate Change

Los Angeles has spent billions at the Owens Lake site to combat the environmental and health impact of dust from the dry lake bed. The site was the largest source of carcinogenic particulate air pollution in North America in the middle of the twentieth century. The US Environmental Protection Agency required Los Angeles to address the dust pollution. The Owens Lake Dust Mitigation Project, begun in 2000, included managed vegetation, gravel cover, buried drip tubing, and irrigation bubblers. It requires a considerable amount of water and by 2023 had cost about $2.5 billion.

Climate change threatens this dust mitigation project. Snowmelt from the Eastern Sierra Nevadas feeds several rivers in California. However, record snowfall in the winter of 2022-2023 led to an historic snowpack melt in the summer of 2023. Dubbed the Great Melt, it filled the bed of Owens Lake for the first time since the aqueduct system was established. The resulting flooding destroyed roads and breached the Los Angeles Aqueduct near the lake's shore. According to the Los Angeles Department of Water and Power, during a wet year like 2023, it manages 1 million acre-feet of water in the aqueduct. This is equal to filling 493,617 Olympic-sized swimming pools. Department officials noted this was the third wet year in six years--both 2017 and 2019 saw high runoff. Huge water flows carry more sediment than the aqueduct can handle, so the department must divert some of the water into the dry lake bed. The water volume threatened berms constructed as part of the dust mitigation project. Excess water was diverted to spreading grounds where it can replenish the water table, but the salty water was detrimental to vegetation planted to control dust.

Mono Lake, whose water levels had been low after several years of drought, also rose by several feet in 2023. As a result, rabbit and sage brushes were sprouting in larger areas and groundwater levels rose. In the 2020s, the Mono Lake Committee, which formed in the 1970s to protect the salt lake, was seeking to reduce the amount of water Los Angeles was permitted to pull from it.

Officials noted that dust was typically not a problem the year after record snowmelt. However, the sediment and damage caused by the water could lead to more severe dust in subsequent years.

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