OCR Text |
Show PART III CURRENT WATERSHED CONDITIONS AND PROBLEMS, AND EFFECTS OF PROBLEMS The areas presently yielding 1.0 to 3.0 ac.ft./sq.mi./year are generally closely associated with easily erodible marine shales such as the Mancos shale. Although they are in near critical condition they could be improved under careful management if they have some soil cover and moderate slopes. However, they have the potential to deteriorate severely under poor management. The forested high country is generally the lowest sediment yield class. On the other hand, it does have a potential for sediment pro- duction as high as 1.0 to 3.0 ac.ft./sq.mi./year. This indicates that continued careful management on these lands is mandatory. These high forest lands can be further improved to produce even less sediment than at present although they are already one of the lowest yielding areas. Much land which is presently rated 0.2 to 0.5 ac.ft./sq.mi./year, shows little potential for reduced sediment yield rates. Yields could increase considerably under conditions of uncontrolled use such as occurred prior to the implementation of management. The land which is presently yielding 0.5 to 1.0 ac.ft./sq.mi./year are primarily in the marine shale and sandstone areas of Utah and the extreme western edge of Colorado. They exhibit a considerable potential for improvement to rates of perhaps 0.2 to 0.5 ac. ft./sq.mi./year. Like- wise, they show a high potential for deterioration under conditions of uncontrolled use as indicated by past yields. From a broad perspective this land generally appears to be responsive to improved management. Yields exceeding 3.0 ac.ft./sq.mi./year are known to exist within the region, but the small size and scattered locations of these areas precluded their specific delineation on the maps. Project planning can reflect and must give detailed consideration to these problem areas and take advantage of opportunities for improvement of their condition. Flood and sediment on forest and rangeland Flood and sediment damage is a problem on approximately 173,000 acres of forest and rangeland within the region. About 41 percent of the affected acreage is in the Green River Subregion, 45 percent in the San Juan-Colorado Subregion, and the remaining 14 percent is in the Upper Main Stem Subregion. Flash floods which are fairly common are a hazard to man and beast. Major flood damage is reflected in losses of highway improvements, fences, livestock, wildlife habitat, and recreation facilities. There is also a significant loss of forage production on flooded sites and a reduction in storage capacity and life of stockwater ponds and reservoirs due to sedimentation. 40 |