RESTORATION POTENTIAL OF THE GROUNDWATER-FED BIG SPRINGS CREEK, SISKIYOU COUNTY, CALIFORNIA

Groundwater-dominated, or “spring-fed,” streams are typically defined by stable hydrologic, water chemistry and thermal regimes reflecting inheritance from local groundwater aquifers. Such stability in hydrology and water quality often leads to characteristic geomorphic and ecological conditions, suggesting a strong potential for the restoration and management of degraded spring-fed streams. This study focuses on: 1) the identification of linkages between hydrology, geomorphology, water chemistry, water temperature and ecological function along the heavily degraded, spring-fed Big Springs Creek, a tributary to California’s Shasta River; and 2) an initial assessment of the stream’s potential response to passive restoration actions following more than a century of cattle grazing along the riparian corridor and within the stream channel. Linkages between the stable, spring-fed hydrologic conditions and channel morphology are dominated by uniformly rectangular channel shapes with high width:depth ratios. Water chemistry and thermal regimes are dominated by large, dispersed springs of constant cold temperatures and notable, geologically-derived inorganic nitrogen and phosphorus concentrations. These high nutrient levels result in both unusually high primary production of aquatic vegetation and secondary production of aquatic macroinvertebrates, which together form the critical base of a food web capable of supporting juvenile salmonids. However, in-channel cattle grazing has denuded stream banks and removed large amounts of aquatic and riparian vegetation downstream from the spring sources, resulting in the progressive widening and shallowing of the stream channel and removal of in-channel and riparian shading elements. Resultant thermal loads produce summertime stream temperatures stressful to most salmonid species. However, the recent exclusion of cattle from Big Springs Creek has resulted in the extensive growth of aquatic macrophytes, successful riparian vegetation planting experiments, apparent channel narrowing and increased channel depths. These preliminary results suggest hydrologic and water quality conditions inherited from the groundwater aquifer can facilitate rapid geomorphic and ecological responses to passive restoration actions.