How do Columbia River dams interfere with salmon migration?

Dams along the Columbia River significantly disrupt the life cycle of salmon by creating physical and environmental barriers to their migration.12

Key ways these structures interfere with salmon include:

• Upstream Migration: Dams act as physical barriers to adult salmon returning to their spawning grounds. While fish passes, such as ladders and locks, are used to help fish surmount these obstacles, their effectiveness has been difficult to sustain as more dams were constructed.1
• Downstream Passage: Young salmon migrating toward the ocean face risks from power-generating equipment. While some can pass through turbines, they are often diverted into fish passes to avoid injury.1
• Habitat and Environmental Loss: Dams have caused the loss of spawning grounds through inundation and have eliminated the natural current that salmon rely on to navigate.2
• Water Quality: Water plunging over spillways can become supersaturated with nitrogen, which is harmful to fish.2
• Population Displacement: The reliance on hatchery-raised fish to supplement populations has led to the displacement of naturally spawned fish.2

These combined factors have contributed to dramatic declines in salmon populations throughout the Columbia River basin.12