Paper No. 2
Presentation Time: 8:20 AM


PENN, Colin A., Geology and Geologic Engineering, Colorado School of Mines, Golden, CO 80401, MAXWELL, Reed M., Geology and Geologic Engineering, Colorado School of Mines, 1500 Illinois St, Golden, CO 80401, ENGDAHL, Nicholas B., Department of Geology and Geological Engineering, Colorado School of Mines, 1500 Illinois St, Golden, CO 80401 and CLOW, David W., Colorado Water Science Center, US Geological Survey, Denver, CO 80225,

Infestation of mountain pine beetle (MPB) throughout the Rocky Mountain Region has caused substantial tree mortality in critical sub-alpine and montane zones. The potential changes in land-energy and water balances caused by MPB tree mortality are demonstrated through hillslope-scale integrated modeling and regional-scale atmospheric modeling using the ParFlow-CLM model for the headwaters of the Big Thompson watershed in Rocky Mountain National Park, CO. ParFlow is a variably saturated, integrated groundwater and surface-water model that solves Richard’s equation in 3D and routes overland flow with Manning’s equation. Parflow is coupled with the Community Land Model (CLM) to incorporate land-surface processes and energy fluxes. The Big Thompson headwaters (358 km2) include sub-alpine and montane zones where forests are experiencing substantial tree mortality. The MPB infestation was documented in the watershed beginning in 1998 with many ecohydrological factors contributing to the rapid spread of infestation and tree mortality since 2007. In addition to vegetation information, data from multiple U.S. Geological Survey stream-gage and water-quality sites in the study area allow for comparisons between model output and observations The ParFlow-CLM model of the Big Thompson headwaters uses a 0.01km2 grid-cell size with variable subsurface depth and is driven by distributed hourly meteorological forcing. Vegetation and associated land-cover changes related to MPB infestations are applied in the model through adjustments to parameters that reflect those found in forest ecology literature. Results at the hillslope-scale show significant changes in transpiration, snowfall, snowmelt, and the near-surface energy balance as a result of MPB tree mortality. Model simulations from MPB and non-MPB scenarios are being compared with observations of streamflow and analyzed for the magnitude of change in land-energy and water balances. This investigation supports regional water-resource management in watersheds such as the Big Thompson that are used for water supply and substantially affected by MPB tree mortality.