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data set provided to us properly characterizes the vegetation, the historical <br />trend simulations are indicative of the cost, in water, of allowing vegetation <br />density to increase. Although we did not specifically address peak flows <br />and low flows, we would expect the nature of the simulated responses to fall <br />within the frequencies and distributions observed on experimental <br />watersheds. Except following fire at lower elevations (5 — 7,000 feet), we <br />would not expect peaks or low flows to be altered. <br />In a very simple empirical model, (Troendle and Reusse, 1997) found that <br />ET in the Sub alpine zone is equal to 18.1 inches of water plus 28 percent of <br />all precipitation in excess of 18.1 inches. Forest removal (equivalent clear <br />cutting) reduces that consumptive loss by almost 50 percent. Increasing <br />forest vegetation adds consumptive use or increases, ET, following the same <br />model. Vegetation manipulation, up or down, has tremendous potential for <br />increasing or decreasing water yield as demonstrated by the scenarios <br />simulated in this analysis and by the research and observational data that <br />represents the foundation for the models used. <br />Acknowledgements <br />We would like to thank Skip Underwood and Mel Mehl, U.S. Forest <br />Service, for their assistance and support in providing the data necessary for <br />this analysis. A special thanks goes to Steve Williams, U.S. Forest Service, <br />MBRTNF for his dedication in providing the data set. <br />Literature Cited <br />Alexander, Robert R. 1977. Cutting Methods in Relation to Resource Use <br />in Central Rocky Mountain Spruce -Fir Forests. Journal of Forestry. <br />75 (July): 395 -400. <br />Anderson, Henry W. 1955. Detecting hydrologic effects of changes in <br />watershed conditions by double -mass analysis. Trans of the Am Geo <br />Union, 36(1): 119 -25. <br />Bates, C. G. and A. J. Henry. 1928. Forest and stream flow experiment at <br />Wagon Wheel Gap, Colorado. U.S. Monthly Weather Review, <br />Supplement 30. Washington D.C. 79 p. <br />45 <br />