Over 20,000 Chinook Return to the Klamath After Historic Dam Removal

A peer-reviewed study finds fall-run Chinook reoccupied 88 percent of their historic range in two seasons after four dams came down, even as drought and remaining barriers still limit full recovery.

Today’s Progress

In the two migratory seasons since crews finished removing four hydroelectric dams on the Klamath River along the California–Oregon border, more than 20,000 fall-run Chinook salmon have moved upstream past the former dam sites into habitat blocked for over a century.

A study published in Scientific Reports on 27 August 2026, led by Damon Goodman of California Trout with partners from the Karuk Tribe, Klamath Tribes, Yurok Tribe, state and federal agencies, and universities, provides the first peer-reviewed quantitative assessment. High-resolution multi-beam imaging SONAR near the former Iron Gate Dam site estimated 7,742 Chinook passed upstream in fall 2024—about 18 percent of the basin-wide return that year—and 13,310 in fall 2025, roughly 19 percent of that year’s return. Combined, the two seasons exceed 20,000 fish.

Ground surveys across about 390 river kilometers of mainstem and tributary habitat found Chinook recolonizing 88 percent of their reconstructed historical range. Inside Climate News reported that water quality improved as warm, algae-prone reservoirs gave way to freer flows, and that imperiled coho salmon, steelhead, and Pacific lamprey also returned within the first year. Goodman told reporters the biological response came faster than most scientists expected, with thousands of Chinook moving into the upper basin and spawning across a large share of historic grounds.

The four dams—J.C. Boyle, Copco 1, Copco 2, and Iron Gate—built between 1918 and 1966 for power generation, blocked passage and altered hydrology until removal concluded in fall 2024, reconnecting hundreds of kilometers of anadromous habitat in the largest dam-removal project completed to date.

Why This Matters

Chinook once made the Klamath one of the West Coast’s most productive salmon rivers. For the Karuk, Yurok, Klamath, and other tribes, the runs remain central to food, ceremony, and identity. A 2002 fish kill of more than 30,000 fish helped galvanize the multi-decade campaign that ended in dam removal.

The demonstrated return shows that when mainstem barriers fall, adult salmon can reoccupy reopened habitat within one to two seasons. That is a concrete ecological result, not a projection. Full recovery of self-sustaining, fishable populations is still ahead and depends on water, climate, and remaining infrastructure—but the recolonization itself is already measured.

Evidence and Context

Evidence strength is high for passage and spatial recolonization: SONAR counts with confidence intervals, coordinated tribal–agency ground surveys, and a Nature-portfolio peer-reviewed paper. Limits remain clear. Remaining dams at Keno and Link River still impede access to Upper Klamath Lake and beyond. In 2024, no fall-run salmon were confirmed past Keno; in 2025 a daytime motion-sensor camera recorded 2,497 fish at Keno and only 210 past Link River into the lake. The Bureau of Reclamation says it is working with Oregon Department of Fish and Wildlife and NOAA Fisheries on passage improvements.

Drought, low snowpack, and elevated temperatures hit the basin hard in 2026. “Removing the dams did not remove climate risk,” Goodman said. George Pess, a former NOAA fisheries scientist now with Conservation Angler, told Inside Climate News dam removal is “not a magic bullet” and recovery will not be “a linear ascent.” Water allotments and rights conflicts continue. The study documents rapid recolonization after barrier removal; it does not claim basin-wide population recovery is complete.

What Made This Possible

Decades of tribal leadership, litigation, and negotiation with PacifiCorp, states, and federal agencies produced the largest dam removal yet completed. Post-removal monitoring combined SONAR, AI-assisted review of imagery, and field surveys by tribes and agencies—turning reconnection into measurable science within two seasons.

Progress Toward Global Goals

The measured recolonization of nearly nine-tenths of historic Chinook range and improved free-flowing conditions align with SDG 15 (Life on Land) and SDG 14 (Life Below Water) through restored migratory connectivity for anadromous species, and with SDG 6 (Clean Water and Sanitation) where reservoir-driven heat and algal conditions gave way to more natural flows. Alignment is tied to these documented outcomes, not to branding. Sustained drought and unresolved passage at remaining dams could still undercut gains if unaddressed.

Building on This Success

The following possibilities were generated with the assistance of AI to explore how this progress might be improved, expanded, or adapted. They are ideas for further investigation, not established findings or recommendations from the people featured in the original reporting.

Passage fixes at Keno and Link River could determine whether upper-basin lake and tributary habitats become fully usable. Actors already named in the reporting—the Bureau of Reclamation, ODFW, and NOAA Fisheries—are assessing conditions; a measurable test would be multi-year counts of adult Chinook and other species successfully entering Upper Klamath Lake and documented spawning there, compared with the low 2025 Link River figure.

Drought-year cold-water refugia management is another conditional path. Reconnected spring-fed tributaries already offer thermal shelter; coordinated flow and diversion decisions among irrigators, tribes, and agencies could be tested by whether juvenile survival and adult holding temperatures stay within known Chinook tolerance bands in low-snowpack years like 2026.

How did Chinook salmon recolonize nearly 90 percent of their historic Klamath range within two years of dam removal?

Barrier removal restored volitional access. Adults that returned to the basin in 2024 and 2025 could swim past the former Iron Gate footprint into mainstem and tributary reaches closed since the early-to-mid twentieth century. SONAR quantified the surge; surveys mapped occupancy against historical extent. The mechanism is physical reconnection plus the species’ migratory behavior—not stocking alone—though hatchery and wild contributions to the overall basin run are part of the broader context. Obstacles that remain (Keno/Link passage, water allocation, climate-driven low flows) explain why recolonization of open habitat is ahead of full demographic recovery.

Three Promising Next Steps

1. Complete and monitor fish passage at Keno and Link River dams — Bureau of Reclamation with ODFW and NOAA; success metric: rising multi-year adult counts into Upper Klamath Lake and verified spawning above those structures.
2. Sustain coordinated tribal–agency distribution surveys through at least one full Chinook generation (roughly three to five years) to distinguish temporary straying from established natural production.
3. Track thermal and flow conditions in reconnected spring-fed tributaries during drought years to test whether dam removal’s resilience benefit holds when snowpack is low.

What Readers Can Watch

• Peer-reviewed follow-ups and agency reports on 2026 and later run sizes past the former Iron Gate site and at Keno/Link River.
• Bureau of Reclamation and partner announcements on Keno and Link River passage projects.
• Tribal fisheries departments’ documentation of natural spawning and juvenile production in upper-basin tributaries.
• Snowpack, temperature, and flow data for the Klamath in successive water years, alongside any temporary flow or diversion measures tied to fish survival.