A large tributary stream, Wooley Creek, joins the mainstem Salmon River about 4 miles (6 km) from its mouth at Somes Bar, and is nearly as large as the North Fork.

The river's 751-square-mile (1,950 km2) watershed is entirely within the Klamath National Forest, and less than two percent of the land area is privately owned.

It retains the only viable population of wild spring Chinook salmon in the Klamath watershed and offers some of the best West Coast habitat for salmon, steelhead, green sturgeon, rainbow trout, Pacific lamprey, and other fish.

Wildfires are the most significant mechanism of ecological change and one of the greatest threats to the river and its watershed.

Fires are a natural part of this ecosystem, but are now often fueled by logging slash and fuels accumulated through decades of fire suppression efforts and therefore burn much hotter, more intensely, and more frequently than they would otherwise naturally burn.