A hearing room with people seated in a semicircular room with reporters with large video cameras and a witness at the witness stand in front of a map display with Mono Lake on it.

Decision 1631

After Mono Lake and its tributary streams had been deemed worthy of protection in the successful Public Trust lawsuit and Fish & Game codes lawsuits, the California State Water Resources Control Board set out to determine what that should look like on the ground.

The result, Decision 1631, is the practical cornerstone of Mono Lake’s protection.

The evidence for Mono Lake

To reach Decision 1631, the State Water Board relied on an Environmental Impact Report (EIR) and an evidentiary hearing.

The EIR, released in May 1993, was an exhaustive, 1,700+ page document with 25 auxiliary reports full of scientific research. The EIR included information about the effects of varying salinities on alkali flies and brine shrimp, historic streamside forest and wetland vegetation, and the effects of different lake levels on tufa groves. It contained results of computer models developed to assess the Mono Basin’s hydrology, examine water supply and demand, and predict dust storms. It also included firsthand accounts and photographs of the Mono Basin before diversions began.

The EIR examined a range of possible lake levels for Mono Lake by considering everything from no water diversions to unlimited water diversions by DWP. The State Water Board received over 4,000 written public comments in response to the EIR, the vast majority of which supported higher lake levels. 

From the outset, the Mono Lake Committee never fought to get all the water back into the lake. The Committee’s strategy was to figure out precisely how much water was needed in order to protect the ecological resources and to fight for that—not more. It was a bold, and clever, strategy—one that paved the way toward a solution that balanced the water needs of Los Angeles and Mono Lake.

The evidentiary hearing began in October 1993 and followed the format of a court trial, with public hearings held in Sacramento, Los Angeles, and Mammoth Lakes. Experts testified about the research in the EIR and members of the public spoke about wildlife, fisheries, recreation, aesthetics, and more. Many witnesses were residents who had lived in the Mono Basin prior to and during DWP’s excessive diversions.

The State Water Board had estimated that about 20 days of hearings would be enough. Instead, it took 43 days to hear all the testimony about Mono Lake. 

A vote, an ovation, and no appeal

On September 28, 1994, the five members of the State Water Board voted unanimously to approve Decision 1631 and amend DWP’s water licenses to protect Mono Lake.

In the State Capitol, beneath a grand mural depicting California history, as the vote was cast, Board member Marc del Piero pronounced: “Today we saved Mono Lake.” State agency decisions didn’t usually get applause, but on that day the crowd in the courtroom stood in a genuine and enthusiastic ovation.

Of the 16 parties that participated in the formal hearing, including DWP and the Mono Lake Committee, not one of them appealed Decision 1631. A decades-long water battle had ended with all parties agreeing to stop fighting and move forward to implement the solution.

How Decision 1631 protects Mono Lake

Lake level of 6392 feet

Decision 1631 mandated that Mono Lake be allowed to rise to 6392 feet above sea level; the “management level.” It is a compromise—while Mono Lake will not rise back up to its pre-diversion level of 6417 feet, it must stay 20 feet higher than its lowest level.

The State Water Board chose that particular management level to reduce the lake’s salinity so that a healthy ecosystem can thrive; improve air quality by covering much of the exposed dry lakebed, thereby reducing toxic dust storms; protect California Gull nesting islets from on-shore predators with a substantial moat of water; and leave scenic tufa towers exposed around the shoreline.

Ties DWP’s exports to Mono Lake’s level

Decision 1631 set water export rules for DWP that depend on Mono Lake’s level.

When Mono Lake is between 6380 and 6391 feet above sea level, DWP can export 16,000 acre-feet of water a year. If the lake drops to between 6377 and 6380 feet, DWP’s exports are reduced to 4,500 acre-feet of water a year. And if Mono Lake is below 6377 feet, DWP cannot export any water.

Once Mono Lake reaches the management level, a new set of rules will apply to DWP’s water exports.

A flexible plan for restoration

Decision 1631 took a flexible approach to mandating stream and waterfowl habitat restoration.

It says that Rush, Lee Vining, Walker, and Parker creek fisheries and forests must be restored, but the actual requirement was for the development of a restoration plan. It set streamflow requirements, but also called for subsequent revision of those requirements in light of improved scientific information about restoration.

This flexible approach produced rules that benefit the creeks built on the best knowledge available at the time, but also recognized that with new knowledge, even better rules could be crafted.

A piece of paper

Decision 1631 built on the Public Trust case and the Fish & Game codes cases, outlining a practical set of rules to guide the Mono Basin’s recovery. But the decision itself was still just a piece of paper that made a promise to the people of California of a healthy Mono Lake and restored tributary streams.

Every day since the decision was issued the Mono Lake Committee has worked to bring the promise on that piece of paper to life. It takes consistent monitoring of conditions on the ground, everyday coordination with DWP about exports and streamflows, and constant vigilance for unexpected challenges. Implementing Decision 1631 to protect the Mono Basin’s Public Trust values is continual, constant work.

Decision 1631 continues to guide restoration at Mono Lake

We celebrated this anniversary with two articles in the Mono Lake Newsletter that year. If you’re interested in the nuts and bolts of Decision 1631, give them a read.

related resources: The State Water Board decision at 20 Newsletter article | The Mono Lake decision at 20 Newsletter article | Public Trust symposium web page

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