A 2017 comprehensive study of salmon, steelhead and trout in California showed that half of the steelhead and salmon populations native to the Klamath River are in danger of extinction within the next 50 years. Removing the four aging hydroelectric dams from the river would significantly improve ecological and geomorphic conditions throughout the Klamath watershed and play a key role in returning these fish to stable population levels.

Iron Gate, Copco 1, Copco 2 and JC Boyle dams create conditions that make it impossible for migratory fishes like salmon and steelhead to survive. These dams completely block passage to historical spawning and rearing habitats. The dams also increase river water temperatures and create ideal conditions for invasive species, salmon disease and the proliferation of toxic algae.

In addition, the dams impede the downstream movement of sediment and large wood, which are key drivers of salmon habitat. They also truncate numerous ecological processes and can change salmon food webs, ultimately reducing habitat suitability.

Reconnecting the Klamath River by removing these dams will provide native salmon and steelhead access to over 300 miles of historical spawning and rearing habitat. These fish are also keystone species and their return to abundance will signify the restoration of critical ecological and geomorphic processes across the Klamath watershed.

Six distinct populations of salmon and steelhead call the Klamath watershed home, and all of them are suffering from degraded habitat conditions associated with dams.

Upper Klamath-Trinity Rivers spring-run Chinook salmon face the greatest risk of extinction. These fish are currently at less than three percent of historical numbers. Blocked from the vast majority of their spawning and rearing habitat, they are extremely vulnerable to stressors including climate change and drought.

Southern Oregon-Northern California Coast Coho salmon are also in critical condition, with a population decline of 95 percent since the 1960s. Perhaps not coincidentally, Iron Gate Dam, which completely blocks passage to cold-water spawning and rearing habitats, opened in 1964.

Klamath Mountains Province summer steelhead mature in fresh water and rely on access to cold stream water during the hottest months of summer, similar to spring-run Chinook. The four lower Klamath dams contribute to reduced flows and the warming of water temperatures during summer, limiting important habitat for this species. Summer steelhead are also in critical condition according to the recently released State of the Salmonids Report.

Southern Oregon-Northern California Coastal Chinook salmon, though stable, are vulnerable to disturbances like wildfires and floods because of their small population size and limited range. Upper Klamath-Trinity River fall run Chinook salmon and Klamath Mountains Province winter steelhead are also in long-term decline, due in large part to a lack of historical spawning and rearing habitat in the upper basin.

Removal of the four lower Klamath dams will begin a long-anticipated recovery for each of these species. Passage to diverse and productive habitats in the upper basin will improve population resilience, ultimately allowing these species to persist in the long-term. Sediment and woody debris will be distributed throughout the system, restoring important habitat diversity and complexity, and enabling these fishes to thrive once again. Dam removal will also encourage historical flow and thermal regimes and help rebuild depleted food webs. With cold water flowing throughout the Klamath, the risk of fish disease and the prevalence of toxic algae will decline.

Dam removal, in tandem with habitat restoration, will support a comeback for these economically and culturally important fish and is the best hope for a resurgence of healthy waters along the Klamath River. Anglers and commercial fishermen, local communities, native tribes, and the fish themselves will all benefit for years to come.

Lusardi is an aquatic research ecologist and applied conservation biologist at the Center for Watershed Sciences and is the California Trout-UC Davis Wild and Coldwater Fish Scientist.