The river's reputation as a world-class steelhead stream and its famous emerald waters are a result of the fact the river source is high enough in the Cascades to derive from snowmelt during the entire year. The melting snow is trapped in volcanic soil and pumice and released during the summer months, providing an even cool-temperature flow. During the summer the flow of the river is approximately 20 times that of the nearby South Umpqua. In its lower reaches, the river's flow becomes increasingly erratic, in a manner typical of mountain streams of the region.