text: The city of Los Angeles diverted water from the Owens River into the Los Angeles Aqueduct in 1913. In 1941, the Los Angeles Department of Water and Power extended the Los Angeles Aqueduct system farther northward into the Mono Basin with the completion of the Mono Craters Tunnel between the Grant Lake Reservoir on Rush Creek and the Upper Owens River. So much water was diverted that evaporation soon exceeded inflow and the surface level of Mono Lake fell rapidly. By 1982 the lake was reduced to , 69 percent of its 1941 surface area. By 1990, the lake had dropped 45 vertical feet and had lost half its volume relative to the 1941 pre-diversion water level. As a result, alkaline sands and formerly submerged tufa towers became exposed, the water salinity doubled, and Negit Island became a peninsula, exposing the nests of California gulls to predators (such as coyotes), and forcing the gull colony to abandon this site.
  In 1974, ecologist David Gaines and his student David Winkler studied the Mono Lake ecosystem and became instrumental in alerting the public of the effects of the lower water level with Winkler's 1976 ecological inventory of the Mono Basin. The National Science Foundation funded the first comprehensive ecological study of Mono Lake, conducted by Gaines and undergraduate students. In June 1977, the Davis Institute of Ecology of the University of California published a report, "An Ecological Study of Mono Lake, California," which alerted California to the ecological dangers posed by the redirection of water away from the lake for municipal uses.
  Gaines formed the Mono Lake Committee in 1978. He and Sally Judy, a UC Davis student, led the committee and pursued an informational tour of California. They joined with the Audubon Society to fight a now famous court battle, the National Audubon Society v. Superior Court, to protect Mono Lake through state public trust laws. While these efforts have resulted in positive change, the surface level is still below historical levels, and exposed shorelines are a source of significant alkaline dust during periods of high winds.
  Owens Lake, the once-navigable terminus of the Owens River which had sustained a healthy ecosystem, is now a dry lake bed during dry years due to water diversion beginning in the 1920s. Mono Lake was spared this fate when the California State Water Resources Control Board (after over a decade of litigation) issued an order (SWRCB Decision 1631) to protect Mono Lake and its tributary streams on September 28, 1994. SWRCB Board Vice-chair Marc Del Piero was the sole Hearing Officer (see D-1631). In 1941 the surface level was at  above sea level. As of October 2022, Mono Lake was at  above sea level. The lake level of  above sea level is the goal, designed to ensure that the lake would be able to reach and sustain a minimum surface level that is generally agreed to be the minimum for keeping the ecosystem healthy. It has been more difficult during years of drought in the American West.