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Show PART II PRESENT STATUS OF IRRIGATION The irrigated lands in the Uinta Basin of Utah are composed mainly of deep, medium to moderately fine-textured soils on gravelly stream ter- races and alluvial fans and moderately deep and shallow soils with strong lime horizons and hardpans on old gravelly benches and mesas. Relatively small parcels are surrounded by nonirrigable lands, mesa escarpments, and eroded sandstone and shale hills. Lands along the east flank of the Wasatch Range of eastern Utah within the drainages of the Price, San Rafael, Dirty Devil, Fremont, Es- calante, and Paria Rivers have mainly deep, moderately fine to medium- textured alluvial soils occurring along the stream valleys in relatively small parcels surrounded by nonirrigable shale hills and mesa remnants. Those in Carbon and Emery Counties are derived primarily from Mancos shale. These are characteristically grayish-brown, slowly permeable, erodible soils associated with severe salinity and drainage problems. The small parcels of irrigated lands in Grand and San Juan Counties of southeastern Utah have many different soils. In the vicinity of Monti- cello, Blanding, and La Sal there are deep, reddish-brown, medium and mod- erately coarse-textured soils of aeolian origin on an undulating topog- raphy. Other soils consist of alluviums of variable textures occurring along stream valleys and on fans and pediments. The Colorado segment of the region presently includes 91^*000 acres of irrigated land. This land varies in elevation from about 4,500 feet in Grand Valley to 9>000 feet in the headwaters of the Gunnison River and other tributaries of the Colorado River. The frost-free period (32° F.) ranges from about 20 days on the higher lands to about 185 days at lower elevations, averaging about 110 days. For grass hay and pasture produc- tion at higher elevations, the growing season is approximately 70 days. Precipitation ranges from about 25 inches at higher elevations to about 10 inches at lower elevations, averaging about 15 inches. The irrigated lands in Colorado include alluvial soils in high moun- tain valleys of the widely branched river system. Stream entrenchment and glaciation have created a variety of land forms, including river flood plains, stream terraces, alluvial fans, and steeply undulating mountain slopes. Most of the irrigation occurs as scattered developments on the flood plains, fans, and gravelly terraces. The soils range in texture from sandy loam to clay loam. Because of the climatic restrictions in the higher mountain valleys, production is generally limited to meadow hay and pasture. At 3_ower elevations the alluvial valley lands are usually grayish brown in color and are highly stratified, varying in texture from loam to clay. They are derived primarily from local shale and sandstone forma- tions. The soils of marine shale origin are inherently high in salt and require considerable drainage and leaching to maintain productivity. 12 |