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,k. . <br />'~., <br />EXHIBIT D-3 <br />Page 5 <br />Soil Mapping Unit 2: Reddish-brown soils of the dry 'Valleys <br />This mapping unit is in Sinbad, Paradox, Lisbon and Big Gypsum Valleys, <br />and Dry Creek Basin. it is not extensive but contains soils used for <br />irrigation and those suitable for potential irrigation. <br />The landscape consists of long, narrow, gently sloping valleys that are <br />surrounded by steep slopes and cliffs. Each valley hae a main intermit- <br />tent drainageways with numerous gullied tributaries. Dry Creek Basin is a <br />wide circular valley surrounded by rolling hills. All drainageways are <br />eroded to depths of 10 to 30 feet and widths of 10 to 50 feet. Cover is <br />dominately sagebrush with rabbitbrush, shadscale, greasewood, and grass. <br />This unit is composed of about 75 percent reddish-brown, calcareous soils <br />with light-colored surface layers that are low in organic matter. Surface <br />layers and subsoils are moderately coarse tb moderately fine textured. <br />Depths to underlying parent material ranges from 30 to more than 60 <br />inches. Most of these soils are suitable for irrigation. Runoff is <br />medium. water holding capacities are moderate to high. About 20 percent <br />of the unit has grayish-brown, moderately fine and fine textured soils <br />derived from Mancos Shale. The organic matter content is low and salinity <br />is moderate. The soils are calcareous throughout the profile. <br />Runoff is rapid and the water erosion hazard is high. The remaining 5 <br />percent consists of shallow soils with gypsum shale or sandstone at <br />depths of 20 inches or less. Most of the gypsum is in the upper reaches <br />of Paradox and Big Gypsum Valleys. These soils have little vegetation <br />and are severely eroded. Runoff is rapid and the erosion hazard is high. <br />Soil Mapping Unit 3: Rock outcrop and very shallow soils of the canyons <br />This mapping unit is along the Dolores and San Miguel Rivers and their <br />tributaries. it is the most extensive unit and constitutes about one- <br />third of the basin. Runoff is very rapid because of the steep slopes and <br />shallow soils with low water holding capacities. Sediment yield is from <br />less than 0.2 to 1.0 acre-feet per square mile per year. <br />The landscape. is characterized by deep sandstone canyons with steep <br />slopes and long very narrow valleys, and floodplains. Small, gently <br />sloping mesas are above the canyons. Steeply sloping alluvial fans <br />border some of the canyon walls. Numerous intermittent drainageways <br />dissect the steep slopes. 'i'he dominant cover is pinyon-juniper. Oak- <br />brush, serviceberry, and grass are more abundant at higher elevations <br />because of increased precipitation. Willows and cottonwood trees occupy <br />small tracts along the narrow valleys. 'there are a few irrigated hay <br />fields where the valleys are wider. <br />1 1 , <br />i• <br />