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Show PREVENTION OF FOREST EROSION Important in its Relation to the Irrigation Water Supply of Western States. Ogden, Utah, January 2, 1920. At least 85 per cent and probably considerable more of the water used for irrigating the 3,200,000 acres of western lands has its origin in the mountains of the National ForesU. The intimate relation that exists between be-tween the National Forests and a sustained sus-tained stream flow for irrigation is therefore readily appeciated. In many mountainous regions where the slopes are steep and the precip-tation precip-tation heavy, floods are liable ti occur. Frequent serious floods and erosion, however are invairably associated with steep, poorly vegetated or denuded water sheds. A well vegetated area, with its abundance of leaves and branches prevents the rain from beating beat-ing directly upon the soil, firmly binda the surface soil layer by the mass of ramifying plant roots, and hence tends " I greatly to minimize erosion. In 1914 two comparable areas, each embracing 10 acres, were located at an elevation of 10,000 feet on the Manti Forest, Utah, for the purpose of determining the effect of varying intensities of grazing on erosion and streamflow. It is hard to believe that as much as a carload, or approximately approxi-mately 50,000 pounds of air dry dirt and rock, is sometimes deposited from a 10 acre area from a single storm. Nevertheless, water and sediment of from 20,000 to 50,000 pounds have been deposited several times from a single storm between 1914 and 1919. What is the effect on forage production pro-duction when the upper few inches of black mealy soil is carried off? The experiment showed, among other things, that wheat plants grown in a poor or eroded soil produced 5 pounds of air dry material as compared com-pared with 12 pounds on non-eroded or good soil of the same general type. It is also significant that much more water was required to produce the 5 pounds of growth on the poor soil than the 12 pounds of air dry matter on the good soil. The effect of serious floods and erosion may be summed up as fol lows: (1) The water holding capacity capa-city of the soil is greatly decreased, and hence crop production is much lowered, (2) the plants that eroded lands will support are inferior for grazing, poison plants being common. (t) it is not possible to make good use of water for irrigation when it gushes down in torrents, (4) the cost I of maintaining the irrigation canals , is very high and (5) the destruction of personal and public property ia often serious. One of the first steps to prevent serious erosion is to revegetate and then maintain the Forest lands to the greatest possible extent. This can " lest be accomplished by applying tho " deferred and rotation grazing sy tern. Department of Agriculture bulletin bulle-tin No. 675 discusses the findinge at the Great Basin Experiment Station of the effect of erosion on forage production. |