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increase, or a 1,464 acre ft increase in water yield. The water yield increase <br />associated with burning (or clear cutting) ponderosa pine is much greater <br />than that which can be attained by partially cutting, as in the earlier example <br />of partial cutting. Water is severely limiting at the elevation the ponderosa <br />pine normally occurs and residual vegetation utilizes any savings from <br />partial cutting. In the Black Hills, where ponderosa pine occurs under wetter <br />conditions, partial cutting can result in increased flow (Troendle and King <br />1987). <br />Because ponderosa pine occurs at lower elevations and in a drier <br />precipitation regime, there is less opportunity to increase water yield. <br />However, the lower elevations are subject to higher intensity rainfall events <br />and storm flow following fire could increase significantly from the <br />ponderosa pine type. Elevated storm response from the higher elevation <br />spruce -fir type is less likely to occur (Troendle and Bevenger 1995). <br />"What if' simulations whether addressing beetle infestation or wild fire are <br />intended to show the potential influence of massive vegetation removal on <br />water yield that may well have occurred in the past, naturally. The <br />simulated increase in flow following the Spruce beetle infestation yielded a <br />result similar to that observed by Love (1955) following an infestation in the <br />White River. The increase in flow from lodgepole pine following fire <br />appears, at first, to exceed the 5.1 inch increase estimated to have occurred <br />from Jones Creek following the greater Yellowstone fires of 1988 (Troendle <br />and Bevenger, 1995). However, after accounting for talus slopes, alpine <br />areas, and other open areas, Troendle and Bevenger (1995) concluded that <br />the "effective" forest area burned on Jones Creek occupied only 55 -60 <br />percent of the total watershed area prior to the fire. In the fire simulation, it <br />was assumed that the stand classes burned were in proportion to those <br />present on the landscape. Over 80 percent of the lodgepole type is in the <br />Pole and Sawtimber classes, at or near complete hydrologic utilization, so <br />the 7.2 inch increase simulated to have occurred from the burned area, when <br />only 10 percent of the basal areas is assumed to survive, seems reasonable <br />and proportional to what was observed after the Yellowstone fire. <br />SUMMARY <br />Several issues stand out as a result of this analysis. First, and perhaps most <br />interesting is the magnitude of the simulated decrease in flow that has <br />occurred over the last 140 years; a decrease of 185,000 acre -feet or more of <br />43 <br />