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<br /> <br />. <br /> <br />. <br /> <br />(- <br /> <br />Geology and Soils <br /> <br />Volcanic rocks of Middle and Late Tertiary age occur at or near the <br />surface throughout mostof the mountain and foothills areas in the uestern <br />part of the watershed. They include rocks of flow origin as well as a <br />variety of rocks of pyroclastic origin, such as tuff, welded tuff, tuff <br />agglomerate, and tuff breccia. <br /> <br />Loosely consolidated sediments of Tertiary and Quaternary age underlie <br />the San Luis Valley. These sediments consist mainly of stream-laid sand <br />and gravel interbedded with silt and clay and were deposited in the <br />gradually subsiding structural basin which forms the San Luis Valley. <br />The maximum thickness of these sediments is several thousand feet and is <br />toward the lower end of the watershed. <br /> <br />Soils of the upper watershed are mainly cold, shallow to deep, medium <br />to moderately fine textured, well-drained, noncalcareous, slightly to <br />very stony. They are either light colored on moderately steep to very <br />steep slopes or dark colored with thick surface soil on gont!y sloping <br />areas. <br /> <br />,~ <br />( <br /> <br />Soils of the lower watershed are varied but consist mainly of either <br />(1) medium to moderately coarse textured, well drained, slightly to <br />strongly calcareous soils on nearly level to gently sloping fans and <br />flood plains or (2) moderately deep to deep, madium to moderately fine <br />textured, dark colored, slightly to moderately saline, sOffiawhat poorly <br />to well drained soils of the valley floor. Other soils of lesser extent <br />are moderately to severely saline, and there are some very sovor3ly alkaline <br />soils. <br /> <br />Land Use and Cover <br /> <br />The distribution of land use and cover for the upper and louer <br />Saguache Watersheds is shown in the following table: <br /> <br />Distribution of Land Use by Watersheds <br /> Acres Square Miles Percent <br /> Upper Lower Upper Lower UppOl" Lower <br /> Saguache Saguache Saguache Saguache Saguache Saguache <br />Item Creek Creek Total Creek Creek Total Creek Creek Total <br />Cropland <br />Irrigated 900 31,100 32,000 1.11 118.6 50.0 .2 6.8 7.0 <br />Range Grass- 21,700 110,800 132,500 33.9 173.1 207.0 11.8 211.11 29.2 <br /> land <br />Multi pIe Use <br /> Land - Timber- <br />Grazing 311.0 1111.11 1152.11 113.8 20.0 63.8 <br />Recreation 199,000 90,500 289,500 <br />~- ..., 221,600 ?~? "00 "5",000 3116.3 363.1 709.11 118.8 51.2 100.0 <br />I w- - -- , . - - <br /> 2 <br /> 0681 <br /> <br />--- - -- <br />- - - - - -- - <br />- --- <br />------------ <br />