Northwestern Great Plains Perennial Spring
Provisional State Rank:
S3
(see reason below)
External Links
State Rank Reason
The number of occurrences is unknown because of the potential occurrence on reservations or private lands. In an inital evaluation of USFS springs in Montana, this ecosystem was evaluated at 30 sites within the Custer National Forest Ashland District, but only five of these contained a high-quality, fully functional S005 community (Stagliano 2004). On subsequent surveys in the Custer Forest (Ashlands & Sioux Districts) numerous perennial spring sites were visited, but very few had intact aquatic communities present (Stagliano 2010, unpublished data 2011). In a similar ecological type, the caddisfly Hesperophylax designatus was also found to be an indicator species of perennial springs in the Glass Mountains of the Great Basin (UT) in a 1994 survey (Myers 1995). Therefore, this ecosystem may be widespread, but because of the limited occurrence of high integrity sites in Montana, long-term monitoring and restoration of degraded sites may be recommended.
General Description
This groundwater dependent ecosystem (GDE) is found in the low-moderate elevation (1000-1600 m), upland hill areas of the Northwestern Great Plains (43) or Northern Glaciated Plains Ecoregion (42). It occurs as small (0.2-2m in width) perennial fishless headwater spring channels with low-moderate gradient geomorphology flowing (<1 L/sec) from sedimentary geology. Benthic invertebrate habitats are typically long riffle/run reaches dominated by shale cobbles and gravel with some woody debris. Surface topography of these springs can range from moderate gradient to undulating or hummocky. Disturbance by cattle is widespread, as these springs often represent the only water source in the uplands.
Diagnostic Characteristics
The S005 ecological system will be fishless. Diagnostic indicator macroinvertebrates of a reference condition spring ecological system (S005) include the midges (Chironomidae) - Odontomesa, Radotanypus, Heleniella, Pseudodiamesa, diptera - Tipula, Dicranota, Ormosia, Pedicia, the snails – Hydrobiidae and Physa; the Mayfly - Baetis tricaudatus, the caddisfly - Hesperophylax designatus, the water mite and leech - Hydrachna and Glossophona complanata, the Beetles - Oreodytes, Optioservus and Hydroporus, and the damselfly larva - Argia. Sediment impaired and cattle degraded springs will quickly lose the mayfly, caddisfly, and dipteran species (above), and form a community dominated by tolerant midges, biting dipterans, and air breathing beetles.
Range
Throughout its Montana range, this seep and springs system occurs within the Custer National Forest, Wolf Mountains, and the higher elevation ponderosa pine forests of the Powder River Basin.
Spatial Pattern
Linear
Environment
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.
Dynamic Processes
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.
Management
Grazing and livestock use around these springs should be limited to a stock tank; immediate spring areas should be fenced to avoid cattle intrusions. Soils adjacent to the springs are often waterlogged and are easily trampled and hummocked by livestock, causing severe streambed degradation, sedimentation, and siltation
downstream.
References
