In the early 20th century, the Los Angeles Department of Water and Power (LADWP) built the Los Angeles Aqueduct to capture snowmelt from the eastern face of the Sierra Nevada and channel water toward L.A. Within a decade, eastern California’s Owens Lake, where the water had naturally flowed and collected for thousands of years, dried up. In 1941, the L.A. utility added an extension that allowed them to drain water from the nearby Mono Basin as well, tapping rivers and streams that had long fed Mono Lake. Mono was best known for its abundant bird life, harboring up to 1 million birds of 300 different species.
By the 1970s, the lake’s plants were dying and dust storms clouded its shoreline. People who loved the lake were worried—including the student researchers, who published their summer research as An Ecological Study of Mono Lake, California, a 200-page report distributed by UC Davis’s Institute of Ecology. The work showed that as the lake’s water level dropped and its salts became more concentrated, its brine shrimp and alkali flies—tiny invertebrates that fed the lake’s birds by the millions—struggled to reproduce. “The present populations of these animals will not be able to withstand the increasing salinity predicted for Mono Lake,” the students wrote. That spelled doom for the lake’s abundant gulls, grebes, and phalaropes.
Armed with these findings, in 1979 a group of environmental organizations sued LADWP over the aqueduct’s effects on Mono, seeking to stop the utility from diverting so much water. They based their argument on the public trust doctrine, a legal principle dating back to ancient Rome that holds that certain natural resources, like navigable waters and shorelands, are held in trust by the state for the benefit of the public. Historically, the doctrine had protected commerce and navigation, barring private landowners from blocking access to waterways below their shoreline’s high-water marks. In 1971, a legal battle over privately owned tidelands prompted California to expand the definition of “public trust” to include those waterways’ habitats and recreational uses. The Mono Lake lawsuit put this brand-new application to the test—successfully. In 1983, the California Supreme Court ruled that protecting Mono Lake’s ecosystem fell under the public trust doctrine. The court left the details to the state water board, who implemented cutbacks to L.A.’s water diversions so that more water would reach Mono and the lake could eventually return to a healthy water level.