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Jrne 1991 Cyprw 7'CC • Sibtidrnre Effiru on Vegetation • 2 ~` runoff is very slow, permeability is moderately slow, and available water opacity is high. Effective rooting depth is 60' or grater. Detailed soil desuiptions are presented in Exhibit 15, Typial Pedon Descriptions, and Exhibit 16, Soil Mapping Unit Desaiptiotu. 2.3 EXISTING VEGETATION 2.3.1 Blg Sagebrush/Meadow Type Based on data presented in current permit documents, existing vegetation within the study area is composed primarily of a sagebrush meadow type chat oaurs in the lowland areaz along Fish Creek. The major spedes in this type include Kentucky bluegrau (Pox pratertsis) and silver sagebrush (Artemisia rana). These two spades account for 55 percent of the cover by all species in this type. Wetland species, like Baltic rush auncus ascticus up. aterJ and species of sedge (Carex scope/orum and Carex praegraci/is), also occur and account for 17.3 percent cover in this type. These species tend to occur immediately adjacent to the stream channel, on low terraces adjacent to the stream channel and in low places on the higher ternces where abandoned stream meanders remain. The sagebrush meadow type is restricted to the mapped alluvial valley floor within the study area. The sagebrush meadow type depends on predpitation, run-on from adjacent uplands, redistributed snow and sub-irrigation az sources of water. Total production (based on 1984 data) for the sagebrush/meadow type was 248 grams per square meter. Of this total, perennial grasses and grasslike plants accounted for 61 percent of the total, 30 percent of • the total waz provided by sedges and rushes, and 8.5 percent of the total was provided by silver sagebrush. Both cover and production data were collected from the entire permit area and, therefore, are a reflection of the type az a whole. Field reconnaissance observations in the study area rugges[ that sedges and rushes are not az prevalent and silver sagebrush is more abundant than in the type az a whole. Some of the major plant spades that occur in the sagebrush/meadow type have water requirements that are greater than what can be provided by predpitation only (Table 1). Supplemental moisture for these spades is provided by sub-irrigation, run-off from adjacent uplands and redistributed snow that tends to collect on the valley floor. Of the spades listed in Table 1, the sedges (Carex spp.), Baltic rush, SidalcPa neomexicarut, and shrubby cinquefoil (Potenti!la fruiuosa) are species that are most dependent on and indiptive of rub-irrigation and usually occur on sites where the capillary fringe reaches the soil surface. If the apillary fringe does not extend into the rooting zone for these spades, they will not persist. Spades like silver sagebrush and Kentucky bluegrass, which require rupplemental moisture, may have roots extending into the capillary fringe, but do not depend to any significant extent onsub-irrigation az a source of additional water. These spades make use of other forms of moisture rubsidies, like runoff from upland areas and redistributed snow. Observations from a site just upstream from the study area, where the stream channel haz recently cut to a depth of 12 to 15 feet below existing stands of silver sagebrush and Kentucky bluegrass, suggest that even when the stream channel is lowered significantly, these vegetation types persist. 2.3.2 Big Sagebrush/Shrubland Type Upland areas adjacent to the bottom-land sagebrush/meadow type support a sagebrush Shrubland type in which big bluegrass (Pox amp(a) and a spades of sagebrush (Artemisia arbrtscu/a) occur u dominant species. Three spades of sagebrush account for approzimately 29 percent of the .[CZ lnc. "P.O. Bos 77!018 • SteamGaat Synngt, Colorado 80177 • (303f879~61ti0