Using Physically Based Hydrology Models to Improve Fine Scale Estimates of Q100 in Complex Mountain Terrain


Tohver, I., Lee, S-Y., Hamlet, A.F.  2012. Final project report prepared for Olympic National Park and Olympic National Forest by the Climate Impacts Group and the Department of Civil and Environmental Engineering University of Washington, Seattle.


Shifts in the timing and quantity of runoff under conditions of a warmer climate in the future will change the frequencies and magnitudes of flood and low flow risks in watersheds throughout the Pacific Northwest. Changes in extreme flow regimes pose considerable challenges to natural resource managers. The Olympic National Forest (ONF) and Olympic National Park (ONP) have formed a partnership to assess the potential effects of climate change on federal lands in the Olympic Peninsula and to revamp management practices that reflect the projected impacts. In support of that effort, the Climate Impacts Group and the Department of Civil and Environmental Engineering at the University of Washington conducted a comprehensive hydrologic analysis on the Olympic Peninsula. We applied the downscaled climate data derived from 10 global models to the Olympic Peninsula at a 1/16th degree (latitude/longitude) spatial resolution to estimate Q100 and 7Q10 statistics for the historical period (1916_2006) and under two emission scenarios, A1B and B1, at three future time intervals: the 2020s (2010_2039), the 2040s (2030_2059) and the 2080s (2070_2099). From these extreme flow estimates, we report the ratio of the each future time interval to the historic period at each grid cell and at the spatial resolution of 4 12_digit hydrologic unit codes (HUCs), or the 6th level watershed classification as delineated by the USGS. The estimates of flood and low flow statistics reported here will support ONP and ONF managers to incorporate projections of climate change_induced shifts in hydrology into their management plans and climate change adaptation assessments.