Editor’s note: This is part of an occasional series on California water issues.

Almost exactly 100 miles due east of Manteca as the California gull flies is the lake that Los Angeles’unquenchable thirst was killing off before a landmark 1983 State Supreme Court ruling.

Mono Lake, which the eastern most reach of Highway 120 skirts its southern shore, had survived at least 760,000 years before the Los Angeles Department of Water & Power extended the Owens Valley Aqueduct 105 miles to the north.

Just as it had done over two decades prior to Owens Lake the City of Angels in 1941 started sucking the life out of Mono Lake by diverting water from the four of the five snow fed creeks that had been flowing into it since before modern civilization.

Fifteen years early in 1926 Los Angeles drained Owens Lake farther to the south dry. The lake in 1900 covered 200 square miles with the depth fluctuating between 21 and 45 feet depending on the Sierra runoff each year.

Owens Lake, which has no outlet, disappeared in just 13 years after Los Angeles started to divert water from its tributaries to fuel the city’s growth and that of the rest of the LA Basin that was clearly unstainable via natural hydrology of the water basin containing the Los Angeles and Santa Ana rivers.

By 1981 — forty years ago after Los Angeles started diverting water from the Mono Lake Basin — the lake dropped by 45 feet, lost half of its water volume, and doubled its salinity.

It had set the stage for an ecology disaster. The most visible victims were California Gulls. The dropping lake created a land bridge to allow predators to reach two islands where 90 percent of the California Gulls were known to nest. As a result there was a large loss of chicks and eggs as predators accessed the islands with ease.

The California Gulls are just one of 98 species that rely on the Mono Lake ecosystem.

Scientists had started cataloguing the unique life of the eco-system that included brine flies and brine shrimp on the assumption Los Angeles would use its water rights to kill off Mono Lake as it did Owens Lake.

In 1976 the first comprehensive ecological study of Mono Lake was conducted by a group of students from UC Davis and Stanford. That led to the formation in 1978 of the Mono Lake Committee dedicated to saving Mono Lake.

A year later the committee along with the National Audubon Society sued Los Angeles. They based their suit on the Public Trust Doctrine that was incorporated into state law. In a nutshell, the doctrine holds that government has a duty to protect navigable bodies of water for the use and benefit of all people.

The case made it to the California Supreme Court in 1983 concurred with the Mono Lake Committee. Its precedent setting decision that is still reverberating through California water issues ruled the state had an obligation to protect places such as “Mono Lake” “as far as possible” even if established water rights had to be reconsidered.

By 1994 Los Angeles finally dropped efforts to work around the decision. They agreed to drastically reduce diversions to make sure the water level was at a level that assured the ecosystem system supporting the brine shrimp and the birds would not collapse.

Within a few years the lake level rose to cover the land bridge.

And while the noted eerie looking tufa towers composed of calcium carbonate — limestone — that is created when carbonate rich saltwater lakes area mixes with spring water are more exposed than they were when diversions started in 1941, the ecological system has been prevented from collapsing.

Los Angeles made up for the loss of water diversions from the Mono Lake basin by instituting California’s first aggressive large scale conservation effort. That effort included recycling water for non-potable uses, giving away free low-flow showerheads, and rising rates in the summer when water use is at its peak to discourage careless consumption.

Mono Lake is considered to be the oldest lake in the United States. At one point in the past it covered much of modern day Nevada and Utah at the end of the last glacial age.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com