What significant legal ruling occurred in 1983 related to Mono Lake's water diversion?

The ruling in 1983 that is significant to Mono Lake's water diversion is centered around the application of the Public Trust Doctrine. This legal principle maintains that certain resources, like water, are held in trust by the state for the benefit of the public, meaning that the state has a responsibility to manage these resources in a way that considers public interest and ecological health.

In the case concerning Mono Lake, the California Supreme Court determined that the state must consider the environmental consequences of water diversions that affect public trust resources. The decision recognized Mono Lake's ecological importance and mandated that the water management practices should safeguard not just human needs but also the health of ecosystems linked to those water sources. This ruling was a pivotal moment in California water law, reinforcing the notion that water rights are not absolute and must be balanced with protecting the environment.

The other options do not pertain directly to Mono Lake's water diversion case. Establishing Delta water quality standards relates to different environmental concerns, the Central Arizona Project is a significant water delivery system unrelated to Mono Lake, and the Reclamation Reform Act addresses land practices rather than direct water quality or environmental issues impacting specific bodies of water like Mono Lake.