| OCR Text |
Show PART III. CURRENT WATERSHED CONDITIONS AND PROBLEMS, AND EFFECTS OF PROBLEMS Recreation area development within national forests has been designed to serve the recreation needs and at the same time anticipate and prevent possible erosion or gullying. In locations of heavy use where inadequate development funds are available, there has been some soil loss. These are usually in undeveloped areas which are heavily used on holidays. Wilderness areas are receiving increasingly heavy use, and this has caused some erosion of trails. Improper logging practices cause severe slope and channel distur- bance. This disturbance results in abnormal runoff and erosion with consequent damage to streams and deterioration of water quality. Normally, the establishment of the next timber crop and the invasion of the disturbed area by native herb and brush species will soon provide cover of sufficient density to stabilize the soil and prevent erosion. Timber sale administration within national forests is designed to cause as little soil disturbance as possible. Where soil disturbance is unavoidable, steps are taken to restore the area to as good condition as feasible. Erosion on cultivated and pasture land Erosion is the dominant problem on an estimated 1,075,000 acres of crop and pasture land. This comprises about 48 percent of the total crop and pasture land and illustrates the magnitude of the problem. Of the total affected acreage about 33 percent is in the Green River Sub- region, 36 percent in the Upper Main Stem Subregion, and 31 percent is in the San Juan-Colorado Subregion. Accelerated water erosion is significant on cropland. Amount of erosion damage is determined by precipitation, soils, slopes, cropping patterns, and management. Sheet and rill erosion are of greatest extent. Surface soil removal reduces crop stands, causes fertility losses and adds to downstream sediment loads. The acreage affected by gullying is small in proportion to the total cropland and pasture, but economic losses are great. Gullies divide fields, interfere with tillage and irrigation practices, endanger dams and diversions, and contribute large sediment loads that affect operation and maintenance of irrigation struc- tures . Erosion on irrigated cropland is most severe on steep slopes that are in row crops like corn and beets. On these slopes it is difficult to irrigate without erosion in the furrows. Loamy surface soils over- lying clayey subsoils and deep, moderately sandy soils on slopes exceeding 3 percent are particularly susceptible to water erosion. |
