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<br />that most of the yield occurred during the June-September growing season and caused a <br />minor increase in peak flows. During periods of drought, the eastern United States may <br />seek low flow augmentation and increased water yields, therefore the potential for <br />increasing water supply from municipal watersheds and further research is needed <br />(Douglass, 1983). <br />3. What are some of the practical limitations to these estimates? <br />• Research treatments tend to be applied to a large portion of small watersheds to assure <br />treatment effect. Larger basins will likely have constraints both physical and legal. <br />-- Studies are from small basins of mostly less than one square mile in size. The largest <br />basin approached 3 miz and may not be representative of larger basins (Coon Creek <br />studies in Wyoming are greater than 3 mi2). <br />• Environmental and other considerations have not been incorporated and limit predicted <br />yield estimates. <br />• Reported annual average runoff is not reflective of what might occur with a 50% chance. <br />-- rarer large flow events drag up the average, but as a practical matter, they are seldom <br />captured and put to beneficial use. <br />• Areas in most need of augmented water axe in drier areas with very limited potential to <br />produce increases from vegetation manipulation. <br />• The increased effect tends to be a constant percentage over the hydrograph. <br />-- this means droughts will remain droughts and floods will be augmented. <br />• Because the largest increases occur in wettest years (3 years in 10 in the southwest), <br />available reservoir storage must be in place to capture and store increased for drought <br />periods. <br />-- Reservoir storage is generally not adequate to realize the increased flows and is not <br />likely to be added in most cases. <br />4. Are there other consequences of increasing water yield? <br />o Yes, some include: <br />-- activation of landslides (particularly Western Colorado, Utah, and Western Wyoming) <br />-- slight increases in channel erosion from flow increase alone <br />-- erosion and sedimentation associated with roads, landing and other disturbance <br />associated with vegetation management <br />-- the need to use herbicide in chaparral to produce a sustained increase by type <br />converting to grass is limiting <br />-- type converted chaparral produces nitrates in water that exceed drinking water