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<br />This map unit constitutes 7.0 percent of the basin. The soils in this
<br />unit occupy benclies, mountai'n slopes, high terraces, hills, ridges,
<br />fans, ti"11 plains, moraines, and valley sideslopes. They are formed in
<br />resl'duum from a variety of crystalline and sedimentary rocks, glacial
<br />outwasli, and colluvial-alluvial material.
<br />
<br />Elevations range from about 8,000 to 11,000 feet (2,438 to 3,353 m).
<br />Slopes range from 2 to 50 percent. The mean annual precipitation ranges
<br />from 15 to 30 inches (P.38 to 0.76 ml. Tlie mean soil temperature is
<br />about 38 to 45 degrees F. (3.3 to 7.20) and the frost free season is
<br />approximately 30 to 75 days. Tliis map unit covers about 337,000 acres
<br />(136,384 ha) - 526 square miles (1,362 km2).
<br />
<br />This unit is used almost exclusively as rangeland, grazed by both cattle
<br />and sheep, but most areas are also grazed by deer. Native vegetation is
<br />usually dominated by big sagebrush. Wheat grasses, fescues,. bromes,
<br />blue grasses and elk sedge furnish most of the forage for grazing.
<br />
<br />The cold climate is severely limiting to all but the most frost tolerant
<br />crops and the low summer precipitation and steep slopes reduce the
<br />suitability for even these.
<br />
<br />Steep slopes, shrink-swell, frost action and frequent stoniness are
<br />1 imiting soil factors to non-agricultural uses.
<br />
<br />Map Unit 60 - Arldic Haploborolls, loamy--Torriorthentic Haploborolls,
<br />loamy--Aridic Argiborolls, clayey, gently sloping to steep.
<br />
<br />This map unit constitutes 3.1 percent of the basin. The soils in this
<br />unit occupy mountain 'slopes, mesas, and canyons, in the form of terraces,
<br />fans, valley side slopes, narrow valleys and flood plains. Tlie soils
<br />over most of the unit are formed in materials weathered in place from
<br />sandstone, shale and igneous rocks. Most of the soils in the smaller
<br />areas of this unit are formed in gravelly, sandy and cobbly alluvium and
<br />glacial' outwasli.
<br />
<br />Elevations range from about 7,500 to 8,500 feet (2,286 to 2,591 m).
<br />Slopes range from about 2 to 45 percent. The average annual precipi-
<br />tation ranges from 15 to 20 inches (0.38 to 0.51 m). The mean soil
<br />temperature is about 40 to 47 degrees F. (4.4 to 8.30 C) and the frost
<br />free period is approximately 75 to 125 days. This map unit covers
<br />150,000 acres (60,705 ha) - 234 square miles (606 km2).
<br />
<br />This map unit is used as rangeland, irrigated cropland, and recreation
<br />and homesite development. Native vegetation in most areas is Gambel oak
<br />and big sagebrush with an understory of fescue, wheat, needle and blue
<br />grasses. Some areas have Pinyon and Juniper and others have clusters of
<br />Ponderosa pine and aspen.
<br />
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<br />A-16
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