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., <br />beetle infestation may recapture much of the decline in water yield caused by growth or <br />re-growth of forest stands over the past 80 or 90 years. Hydrologic impacts that may <br />result from insect infestations are also occurring to some extent in other forest types and <br />on other land not considered in this study so the impact of the infestations on water yield <br />from the entire basin might be quite significant. <br />As part of the hydrologic evaluation of the North Platte River Basin a number of U. S. <br />Geological Survey stream gauges were identified that were suitable for use in <br />documenting future changes in streamflow (Troendle et al. 2003). A double-mass <br />analysis procedure was used that relied on comparing the stability of response at one <br />gauging site with response at other control sites. Some of the potential control sites <br />identified were other stream gauges while some were long-term rain gauge or snow <br />course monitoring sites. Monitoring sites in both the North Platte and South Platte River <br />Basins were identified as stable and useable. Because of the widespread invasion of the <br />mountain pine beetle, stream flow is likely to be impacted to some degree at all the <br />streamflow monitoring sites in both the North and South Platte River Basins. However, <br />this may not be the case for the rain gauge and snow course sites that were, or others that <br />could be identified as useable. These sites can continue to be used as reference sites to <br />document flow changes over time. Site visits to the precipitation sites would be <br />mandatory to document that site (vegetation) changes were not occurring as a result of <br />the infestation and that the measurement is still valid. In addition, one would want to <br />verify that measurement at a particular precipitation site is not being impacted by other <br />off-site activities such as cloud seeding. It should also be noted that if cloud seeding were <br />occurring on watersheds of interest, the effect of that practice on streamflow, if any, <br />would need to be partitioned as well and that could de done by careful selection of <br />reference gauges. Given that precipitation monitoring sites (rainfall and snow pack) can <br />be validated to be stable, and they have been shown to compare well with streamflow <br />even when far removed from the stream gauging site, it would be possible to identify an <br />existing monitoring network capable of documenting future changes in water yield. <br />Given the potential magnitude of the current beetle infestation, identifying such a <br />monitoring network would be appropriate at this time. Detection of change would be <br />cumulative in nature and require several years of monitoring before departure could be <br />validated (Troendle et al. 2003) but appropriate and useable monitoring sites should be <br />identified as quickly as possible so that their integrity and availability can be insured into <br />the future. <br />The recent occurrence of a catastrophic fire and the potential impacts of the current insect <br />infestations, both hydrological and ecological, attest to the natural dynamics of <br />streamflow generation from forested land. <br />LItef"atUre CIte <br />Bethlahmy, N. 1974. More streamflow after a bark beetle epidemic. Journal of <br />Hydrolology, 23: 185-189. <br />Bosch, J. M. and J. D. Hewlett. 1982. A review of catchment experiments to determine <br />the effect of vegetation changes on water yield and evapotranspiration. Journal of <br />Hydrology. 55: 2-23. <br />27 <br />2/2/2007