PRELIMINARY INVESTIGATIONS INTO THE IMPACT OF METAL TRANSPORT ACROSS THE GROUNDWATER/SURFACE WATER INTERFACE DUE TO THE MOUNTAIN PINE BEETLE EPIDEMIC: PENNSYLVANIA CREEK, SUMMIT COUNTY, COLORADO

The mountain pine beetle (MPB) epidemic in Western North America has generated growing concern in recent years. Increasing numbers of outbreaks have affected an estimated two million acres of forest in Colorado and Wyoming alone during 2008. Given the substantial acreage of prematurely dying forests within the Colorado mineralized belt, it has been hypothesized that the effects of the MPB outbreak will be similar to those observed after forest harvesting. We hypothesize that physical phenomena typically experienced after deforestation, such as increased erosion and runoff, will affect the transport of metals through the groundwater/surface water interface. Summit County, Colorado provides an excellent field site for researching the MPB impacts as specific reaches of Pennsylvania Creek have been affected by MPB while others have remained untouched. A previous characterization of Pennsylvania Creek drainage identified a course-grained sandy subsurface with no identifiable aquitards to inhibit flow (Smith, 2004). Over the past 15 years groundwater levels have slightly increased, despite the increased development of the area. Field data from Pennsylvania Creek and surrounding areas are being collected and analyzed to determine the physical relationships between the groundwater and surface water and to lay the groundwork for long-term observation of metal fluxes. Currently, measurements are taken on a timescale to understand the daily and seasonal fluxes of water between the groundwater and surface water at multiple locations along a two mile reach of Pennsylvania Creek. Pressure transducers have been installed in three different locations to record the water level in the creek at 15 minute intervals with concurrent groundwater levels measured hourly at three additional locations. Salt dilution gauging has been implemented on a weekly basis to monitor the flow of the creek. Preliminary findings support the expected correlation between the flow and the pressure transducer’s recorded output. Surface water samples are analyzed for metal constituents using ICP-AES at locations corresponding to high MPB impact and no observed MPB impact. The implications of these results for the transfer of metals through the groundwater/surface water interface are presented along with plans for future monitoring.