April 8, 2022 — Shasta Dam stands more than 600 feet tall, the height of a 55-story building, with a colossal spillway that towers over the Sacramento River in a curved face of concrete.
Since its completion in 1945, the dam has created California’s largest reservoir, which provides water for farms and cities across the state. But it has also blocked Chinook salmon from returning upstream to the cold, spring-fed streams near Mt. Shasta where they once spawned.
Cut off from that chilly egg-laying habitat, endangered winter-run Chinook have struggled to survive. They’ve had help from an elaborate spawning operation at a government-run fish hatchery, which is intended to function like a life-support system for the salmon.
But that support system is no longer enough. As global warming fuels worsening drought conditions and extreme heat, experts say winter-run Chinook are being pushed to the brink of extinction.
Last year, the water flowing from Shasta Dam got so warm that it was lethal for winter-run salmon eggs. Most of the eggs and young fish died. State biologists estimated that only 2.56% of the eggs hatched and survived to swim downriver, one of the lowest estimates of “egg-to-fry” survival yet.