Critical habitats necessary to support cold-water species in lotic ecosystems are anticipated to diminish as global climate change reduces summertime availability of cold water in streams.  Volcanic spring-fed streams may prove an exception to this habitat loss as large aquifers with high residence times produce reliable stream flow for sustaining cold-water species.  Here, we identify a hitherto overlooked exceptionally productive and resilient environment in which large groundwater springs located within volcanic arcs provide consistent cold-water stream flow and ecologically significant nitrogen and phosphorus inputs from geologic sources.  In the spring-fed Shasta River of northern California, steelhead trout take advantage of abundant food and stable year-round flow and water temperature regimes to accrue a substantial growth advantage over individuals from an adjacent non-spring-fed stream, exhibiting a six-fold increase in mass and two-fold increase in length.  Results demonstrate that geologically-derived nutrients in spring-fed streams are driving aquatic ecosystem productivity and resiliency, making these habitats exceptionally important for conserving cold-water species impacted by global climate change.