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Show From 60 to 75 percent of the total annual water yield comes from the forested areas in the eastern and southern parts of the basin. The balance comes from the unforested agricultural areas mainly in the north and west portions. Average water yields from the forested mountainous areas exceed 30 inches annually, while average annual water yields from the agricultural areas are less than 15 inches. Although the degree of erosion in the Ohio Basin is not so severe as in some other basins, soil erosion and the accompanying loss of soil fertility are critical problems in many areas. Field studies have shown that: in the Green River watershed in Kentucky and Tennessee all of the original topsoil (average depth 6 to 10 inches) has been removed from over one-fourth of the land; in the Muskingum water- shed erosion has removed about 50 percent of the original topsoil from the hilly areas and about 25 percent from the level glacial soils; and in the Patoka and East Fork of the White River watersheds in Indiana, topsoil losses average more than 4 inches. The potential increase in farm output resulting from improved production methods in recent years has been offset somewhat by erosion damages. Ero- sion separates the organic matter, and fine soil and water movement carries away these materials which contain most of the essential plant nutrients. The low nutrient content of the coarse material which remains to support plant growth lowers the production potential of the soil. Experiments conducted in the Muskingum water- shed on areas with topsoils of 7 inches or less show that corn yields are reduced 3 bushels an acre for each inch of soil lost; oat yields are reduced 1x/z bushels an acre; and hay yields decrease by 200 to 400 pounds an acre. Long and continued use of croplands within the basin with inadequate soil-building rotations, poor cover, and improper methods of cultivation have contributed to the accelerated soil erosion and de- pletion of these lands. Serious erosion problems exist in the rolling and hilly areas of the watershed as a result of active sheet erosion, gully erosion, stream bank cutting, and flood plain scour. Sedi- mentation and silting are the result of erosion, pri- marily from unprotected croplands, although also from pastures, deteriorated forest lands and woods, and other watershed disturbances. Classifications of land use show about 42 million acres of cultivated land, 32 million acres of forest and woodlands, and more than 15 million acres of grassland in the basin. The remaining 9 million acres have miscellaneous uses such as town sites, industrial sites, home sites, rights-of-way, lakes and streams, etc. Of the 32 million acres in forest and woodland, about 29 million are privately owned and 3 million are in public ownership. Approximately 2 million acres are national forests and 1 million acres State and county forests. Most of the privately owned forests and woodlands are in small holdings, mainly farm woodlands. However, numerous relatively large holdings of mine, lumber, and industrial own- ers are scattered throughout the forest region, especially in the rugged eastern mountains. Overcutting, burning, grazing, and improper log- ging methods have depleted extensive areas of for- est. Increased surface runoff and erosion occur where forest cover is destroyed. It is estimated that accelerated erosion has removed more than 75 per- cent of the topsoil from about 25 percent of the forest and woodland areas in the basin. Moderate erosion on an additional 25 percent of these lands has removed from 25 to 75 percent of the topsoil. More than 7 million acres of the 15 million acres of pasture land need rehabilitation. Overgrazing, improper management and distribution of livestock, and inadequate fencing and watering facilities are factors which have contributed to depletion of grass- lands. Poor pastures contribute heavily to flash runoff and sedimentation problems. Land use capability studies for private rural lands indicate that of the 42 million acres now in cultivation, 4 million acres should be retired to per- manent pasture and 1 million acres should be re- tired to woodland. Of the 15 million acres in grass, 640,000 acres are suitable for cultivation and 2.3 million should be devoted to forest production. Of the 32 million acres of woodland, 620,000 acres are suitable for cultivation, and 540,000 acres are suitable for permanent pasture. Changes in land use recommended by these studies would reduce the total cultivated lands to 38 million acres and pas- ture and woodland would be increased to approxi- mately 17 million and 34 million acres respectively. A combination of soil treatment and improve- ment practices with protection measures and water disposal systems is needed on most of the crop and pasture lands in the basin. Soil amendments and fertilizers are needed so that adequate forage, cover, and rotation crops can be produced. The variations in climate, topography, and soil throughout this basin present complex problems of 643 |