Small Volume Spring Stream
Provisional State Rank
* (see reason below)
State Rank Reason
The number of occurrences of this system is fairly well known and many spring creeks fall within private property. Very few spring creeks have had extensive biological inventories due to private land issues, but the potential of discovering new snail species is high (D. Gustafson, pers. comm.). Due to the constant
temperatures, these streams can act as fish refuges during the summer and winter months, with trout spawning areas on the gravel bottoms.
This ecosystem is found in the Montana Foothills and Valleys Ecoregion. Elevation is 1200-2000 m. These small volume spring streams (average wetted width 1.3 m, >1 and <5 L/sec, average summer temperature <15°C, S003m-Warm springs - will have water temperatures >25°C) have moderated permanent flow with strong seasonal variability. Waters are mineral-rich and circumneutral to alkaline with pH of 7.0-8.2; clarity is often high. These factors contribute to lush growth of submerged aquatic vegetation, which may include watercress Nasturtium officinale, Potamogeton spp., and Myriophyllum spp. These streams represent groundwater discharge input, therefore they do not experience severe flooding or drastic temperature shifts and have more constant flow. The substrate of these streams is usually cobble riffles, gravel/sand runs and pools, with extensive beds of aquatic vegetation, and, unless
they are degraded by cattle, flow silt-free and clear.
The S003 ecological system could be fishless because of its small volume and limited accessibility to a colonization pool of fish, and small warm springs (S003m) may be too warm to allow fish colonization. If present, the spring creek fish community historically had native species including westslope cutthroat, mottled sculpin, longnose dace, with Yellowstone cutthroat trout in the Yellowstone drainages. However, the introduced brook, brown, and rainbow trout tend to dominate and become the focal species of these systems. Abundant populations of spring creek macroinvertebrate communities are diagnostic because of the stable environment, but display relatively limited diversity. This fairly unique, low-diversity community consists of a combination of members from the Medium Coolwater Transitional, the Traditional Trout Stream, and the Foothills Transitional Assemblages. The community is dominated by the mayflies (Tricorythodes and Ephemerella spp. [usually Ephemerella inermis and E. infrequens]), the amphipod crustaceans (Gammarus and Hyalella), and many genera of Chironomidae. Other community indicator species include Baetis tricaudatus, caddisfly species (Hydropsysche, Amiocentrus aspilis, Cheumatopsyche, and Brachycentrus occidentalis), beetles (Optioservus spp.), and snails (Gyraulus, Physella, Stagnicola, and Hydrobiidae). An S003 spring near Townsend, Montana (Bedford's Spring) is home to an endemic springsnail of the genus, Pyrgulopsis , one of the only places this genus is found east of the continental divide.
The Spring Creek type has been identified in the foothill and valley ecoregion of many Montana drainages, particularly some of tributaries to larger valley streams: Bedford Spring Creek, Ben Hart (tributary to the E. Gallatin), O’Dell Creek (tributary to the Madison), Warm Spring Creek of the Missouri drainage.
Surface topography usually has a moderate gradient but can be undulating or hummocky. Disturbance by cattle is widespread, as these springs often represent the only water source in the uplands.
Spring water ecosystems are tied to climate, groundwater discharge, and water quality. Impacts to these parameters as well as their natural variability will have a corresponding effect on spring biological ecological systems. Long-term drought, groundwater withdrawal at local and regional levels, and local diversions at or near the orifice are common impacts on water quantity at spring sites throughout the Western United States.
Livestock use around the riparian areas is common and can have strong local effects resulting in sedimentation and streams becoming wider or shallower. High-density cattle usage can cause severe
degradation, sedimentation, and siltation on the riffle habitats and gravel spawning areas downstream.