Montana Field Guide

This groundwater dependent ecosystem (GDE) is found in the moderate elevation (1000-1600m), upland hill and canyon areas of the Wyoming Basin (18). It occurs as small (0.2-2m in width) perennial fishless headwater spring channels with low-moderate gradient geomorphology flowing from sedimentary geology. We identified 2 types of this ecological system: Limnocrenes — non-linear flowing springs, lentic spring ecosystems that resemble small wetlands (WPSS-Wetland /Ponded Seep Springs), and Rheocrenes – flowing water springs that may flow into perennial or ephemeral streams or may disappear into the ground some distance from their source (Table 2 & 3). Secondarily, Rheocrenes can be separated into dispersed wall spring seeps, a.k.a. hanging gardens (LVWS-Low, MVWS-Med or High Volume Wall Springs & Seeps) or linear flowing channelized springs (STCS-Single Thread Channel Springs). 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 in the ponded wetland areas.

The S006 ecological system will be fishless. Diagnostic indicator macroinvertebrates of a reference condition Wyoming Spring ecological system (S006) include the Caddisflies - Hesperophylax designatus and Lepidostoma unicolor, Stoneflies: Amphinemura banksi and Hesperoperla pacifica; the Mayfly - Baetis tricaudatus, the aquatic Beetles - Heterlimnius corpulentus, Optioservus and Hydroporus; midges (Chironomidae) - Parametriocnemus, Brillia, and Tvetenia bavarica. Other Diptera - Tipula, Dicranota, Ormosia, the snails – Hydrobiidae and Physella. Sediment impaired and cattle degraded springs will quickly lose the mayfly, stonefly, caddisfly, and dipteran species (above), and form a community dominated by tolerant midges, biting dipteran larvae (Ceratopogonidae), and air breathing beetles.

This seep and spring ecological system occurs within the Wyoming Basin ecoregion in Montana, especially within the Pryor Mountians and Bighorn Canyon National Recreation Area.

Linear

Surface topography usually has a moderate gradient, but topography 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.

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.