Columbia Basin Passage Barriers
Not all of the Columbia River Basin is accessible to salmon. Some areas are blocked naturally behind major waterfalls that formed a passage barrier. Other area have been blocked by human interference, primarily dams without fish passage. This map shows both types of blocked areas in the basin. Click here to download a 11×17 high-resolution PDF version of this map suitable for printing.
Historically, salmon migrating up the Snake River were blocked by Shoshone Falls, near present-day Twin Falls, Idaho. Today, salmon are blocked 370 miles downstream from Shoshone Falls by the Hells Canyon Dam, which has no fish passage facility.