WSP06617 - Laserfiche WebLink

Home Browse Search

0833:"4 CHAPTER II LAND AND WATER RESOURCES . profile development with a high organic content in the surface ?;one. High precipitation has also leached the soils of lime and all but a trace of soluble salts. The influence of pine tree cover has also resulted in neutral or slightly acid soils. Textures vary from silt loams to clay, with both medium- and heavy-textured soils occurring in the same profile. Areas of shallow soils over shale or sandstone are common. A typical soil profile shows a 12- to 18-inch surface zone of brown or dark grayish-brown platy to semiblocky silt loam or clay loam. This zone contains a high percentage of organic material. Underlying the top soil, there is generally a moderatly heavy clay pan of yellowish-brown or reddish-brown blocky clay loam or light clay. '!he top soil appears to. be very fertile, possesses good available moisture capacity, and has good penneabil1ty, as shown by penneabil1ty tests of disturbed soil. The sub- soils have lower fertility and slower penneability rates. Variations from the typical profile occur as a result of changes in the surrounding geolog- ical fonnations. Where Mancos shale predominates, the soils are heavier and have a dark grayish-brown color throughout. The soils derived from Dakota sandstone are lighter in texture and color. . Lands in the vicinity of the project include timbered and nontimbered areas. The nontimbered lands lie in open grass- and weed-covered parks, while the timbered lands are covered with ponderosa pine, oakbrush, grass, and weeds. Topography '!he lands have a characteristically undulating surface marked by rolling ridges and frequent shallow swales. The side slopes of the ridges vary from 2 to 8 percent. Irrigation runs will be short, in most instances varying from 200 to 400 feet in length. Since the lands are not conducive to leveling, little preparation for irrigation will be necessary on the nontimbered lands. On timbered lands, or those covered with oakbru.sh, rather expensive clearing operations will be necessary. 'lhe timbered areas, however, are not extensive. Drainage The project lands are dissected by many natural drainageways, which should provide adequate surface drainage for most of the area. Some water- logging occurs during the wet season in several narrow swales and bottom lands located adjacent to p,roject lands. In general conditions are not adaptable to the use of subsurface drains. Project drainage would be limited largely to surface drains and the improvement of same of the smaller restricted natural drainage channels. . Water Resources Irrigation system lIlperation studies ."ere based on streamflows over the 25-year periOd, 1928 through 1952, which includes the 10-year critical low 10