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~ • Pie 2 • ~~ i '1"ne General Soil Idap was prepared by delineating eight mapping units that differ from each other in the kinds of soil that are present. The soils in each mapping unit .are associated and form patterns that are repeated from . place to place. They were defined and described according to requirements imposed by the map scale and criteria from the Comprehensive System of Soil Classification, adopted in January 1965. The composition of the units ~ along with related characteristics and interpretative information are shown :; in Table 1. Readers interested in more detailed information about the ': ' classification system ;should consult technical`publications. 1/, 2/ ;.~ •} ~ ; Acreage..distribution of napping units and percent that each occupies is ' given in Table 2.: Composition and related characteristics of each soil ~~ ~ mapping unit are .given in the following brief narrative descriptions. ,~ Soil Napping Unit'1: Lei ht-colored soils of the deserts i This unit is in Disappointment Valley, mostly in San A;igvel County, but a small part extends into Dolores County. This unit is one of the least extensive in the basin. S,ater intake is slow and runoff is 'rapid .'; Erosion ~ is moderate to severe and sediment yield is in the ranoe of 1.0-3.O acre- ~ feet per square mile per year. , The landscape is characterized by a wide oblong valley with rolling shale • hills on the north and east and steep barren shale hills to the south- : cast. There are many internittent drainagcways into Disappointment Creek. hto st of these drainay-cways are eroded to depths of 10 to 20 feet and widths ' of 10 to 50 feet. A sparse cover of shadscale is ore sent with some sagebrush, rabbithrush, and areasewood along the drainaaeways. On the upper reaches of the valley there are a few pinyon-juniper. _ There are three major groups of soils in this unit. Shallow soils derived from 1•;ancos Shale make up about 50 percent of the unit. They have light- colored, calcareous, surface layers, are low in organic matter and have fine and moderately fine textures.. These soils are on rolling hills, mainly ' on the north and east side of Disappointment Creek. Another 35 percent of the unit consists of deep and moderately deep fine textured alluvial soils. These soils are along Disappointment Creek. They usually have light-colored surface 1,,-,yors although in the upper reaches of the valley they become darker. The soils are moderately saline-alY.ali and have a slow permeability rate. The remaining 15 percent of the unit consists of reddish-brown, moderately deep soils on small terraces, mainly on the south and west side o£ Disappoiniment Creek. Surface layers are light-colored and the pei~aeability late is moderate. _1/ .Soil Survey Staff, SCS, USDA _.. "Soil Classification, a Cor,~prehensive System 7th Approximation,"- 1960 and as ~Jnendcd through October 1966. ~' 2/ Aandahl, Andrew R. "T]ie First Comprehensive Soil Classification System" Journal of Soil and Water Conservation 20:243-246, 1965.' ~;