Numerical experiments to explain multiscale hydrological responses to mountain pine beetle tree mortality in a headwater watershed

Colin A. Penn, Lindsay A. Bearup, Reed M. Maxwell, David W. Clow

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32 Scopus citations


The effects of mountain pine beetle (MPB)-induced tree mortality on a headwater hydrologic system were investigated using an integrated physical modeling framework with a high-resolution computational grid. Simulations of MPB-affected and unaffected conditions, each with identical atmospheric forcing for a normal water year, were compared at multiple scales to evaluate the effects of scale on MPB-affected hydrologic systems. Individual locations within the larger model were shown to maintain hillslope-scale processes affecting snowpack dynamics, total evapotranspiration, and soil moisture that are comparable to several field-based studies and previous modeling work. Hillslope-scale analyses also highlight the influence of compensating changes in evapotranspiration and snow processes. Reduced transpiration in the Grey Phase of MPB-induced tree mortality was offset by increased late-summer evaporation, while overall snowpack dynamics were more dependent on elevation effects than MPB-induced tree mortality. At the watershed scale, unaffected areas obscured the magnitude of MPB effects. Annual water yield from the watershed increased during Grey Phase simulations by 11 percent; a difference that would be difficult to diagnose with long-term gage observations that are complicated by inter-annual climate variability. The effects on hydrology observed and simulated at the hillslope scale can be further damped at the watershed scale, which spans more life zones and a broader range of landscape properties. These scaling effects may change under extreme conditions, e.g.; increased total MPB-affected area or a water year with above average snowpack.

Original languageEnglish (US)
Pages (from-to)3143-3161
Number of pages19
JournalWater Resources Research
Issue number4
StatePublished - Apr 1 2016
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Water Science and Technology


  • hydrology
  • integrated modeling
  • mountain pine beetle
  • scaling


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