Willow Creek flows as a tributary to Clear Creek in Shasta County, eventually feeding into the larger Sacramento River system. This creek has been significantly impacted by historical mining activity, particularly metals contamination from the abandoned Greenhorn Mine operated in the early 1900s. Despite these challenges from the copper mining legacy, monitoring data shows that the contamination from the Willow Creek drainage has not caused significant downstream impact on Clear Creek itself. The upper Clear Creek watershed, which Willow Creek joins just upstream of Whiskeytown Reservoir, generally maintains good water quality and supports healthy aquatic populations.