A Second Aqueduct

The challenge of water supply continued to press.  While the City had taken virtually its full Mono Basin entitlement for several years between 1941 and 1970, it found it could not divert the full amount authorized by the 1940s water rights permits on a long-term basis without constructing additional conveyance facilities downstream from Mono Basin.  The Water Rights Board and the Department of Water Resources urged the City to take steps to develop its full entitlement or risk the potential that other appropriations might be granted by the Water Rights Board.

At the same time, a U.S. Supreme Court decision in 1963 (Arizona vs. California) had allocated Arizona more water from the Colorado River, reducing MWD’s entitlement to Colorado River water by more than 50%.  In addition, water from the MWD was expensive because of the high energy costs involved in delivering it.  This consideration, plus the availability of higher quality water, led to a decision to bring more Eastern Sierra water to Los Angeles.

The Second Los Angeles Aqueduct, an $89 million dollar facility, was completed in 1970.  Beginning at Haiwee Reservoir, just south of the Owens dry lake bed, this project was shorter half as wide as Mulholland’s “ditch,” and was easier to build as a result if improved construction equipment and the lower cost of steel pipe.  The new aqueduct added another 50% capacity to the water system.  The two Los Angeles Aqueducts now deliver an average of 430 million gallons a day to the city.

Under normal circumstances, 70% of the city’s water comes from the Eastern Sierra.  Wells in the San Fernando Valley and other local groundwater basins supply 15%, and purchases from MWD furnish the last 15%.  From a system of ditches and waterwheels in the 1780s, the system has grown to 105 reservoirs, including four major reservoirs along the aqueduct system.

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