That river, Nelson points out, is "the most important salmon-producing system south of the Columbia River." But California authorities haven't required the federal Bureau of Reclamation, which owns and manages the dam, to meet temperature standards downstream of the dam, even though it has the power to do so. "The state just hasn't done its job," Nelson says.

Talk to stakeholders in the salmon fishery, and one term keeps cropping up: "water management." Their point is that drought isn't the most important factor in the survival of the species — policy is, specifically the management of water supplies so that they're balanced among users and serving irrigation demand from farmers doesn't wipe out competing interests, especially during dry years.

To better understand the threats to salmon, it helps to know about their life cycle. Salmon live and breed on a three-year timeline. Adult fish swim in the ocean, but migrate upstream to lay eggs in the gravel beds of inland rivers. After they hatch, the baby fry and juveniles, called smolt, begin migrating downstream, typically via San Francisco Bay, and out to sea. Then the cycle begins again.

The critical period for the fall-run salmon in the Sacramento is while the eggs are incubating in their gravel beds. At water temperatures of 54 degrees, they start being cooked to death. Irrigation releases from Shasta suck down the reservoir's cold water, leaving surface water heated by the sun; that's what ends up in the Sacramento River at spawning season.

In recent years, water in the spawning beds has been measured at 70 degrees or higher. In 2021, state biologists reported, 99% of winter-run Chinook salmon failed to reach the San Francisco-San Joaquin River delta and the bay.

"Salmon have survived droughts in California for millennia," says Scott Artis, executive director of the Golden State Salmon Association. "But when on top of that you have incredible water diversions and temperature pollution, that's what's killing these baby fish. And when you kill the baby fish, they don't come back as adults."

The need for painstaking water management is the result of human interventions in California's natural environment. Over the last 100 years, rivers across the Central Valley were dammed to provide irrigation for farms, blocking salmon from their natural habitats. The federal government opened salmon hatcheries to compensate, but they have not produced enough fish to make up for the losses from poor water management.

Meanwhile, the water demands of California growers became less flexible. Crops that could be fallowed during dry spells, leaving more water for the environment, were supplanted by almond and pistachio orchards, which require water in wet years and dry. California almond acreage rose to 1.38 million last year from 418,000 in 1995. In the same period, pistachio acreage rose to more than 461,000 from 60,300.

The crisis that has unfolded in 2023 and this year has its roots in actions taken during the Trump administration. In 2019, Trump installed David Bernhardt, a lobbyist for agricultural water users, as Interior secretary.

As an attorney in private practice, Bernhardt had sued the government on behalf of the giant Westlands Water District to challenge its enforcement of the Endangered Species Act, which conflicted with Westlands' interests. As Interior secretary, Bernhardt advocated for loosening enforcement of the act.

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