improving estimates of hydrologic extremes: applications to the olympic national forest ingrid...
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Improving Estimates of Hydrologic Extremes:
Applications to the Olympic National Forest
Ingrid TohverPNW Climate Science Conference September 14, 2011Seattle, WA
Partnerships with Stakeholders
Olympic National Forest and Park:
Kathleen O’Halloran
Luis Santoyo
Bill Shelmerdine
Robert Metzger
Robin Stoddard
Climate Impacts Group &
Civil and Environmental Engineering,
University of Washington:
Alan Hamlet
Se-Yeun Lee
Ingrid Tohver
Robert Norheim
Project Premise
• Assess potential impacts of climate change on federal lands and incorporate projections into management practices
• Update estimates of extreme streamflows
• Support protection of fish and wildlife habitat
• Support road maintenance and flood control infrastructure
Photos courtesy of Olympic National Park
USGS Streamstats Tool
Web-based GIS tool used to estimate streamflow statistics:
Inputs = basin size, annual precipitation and elevation
• DEM & PRISM datasets
Regression equation developed by USGS calculates statistics
http://water.usgs.gov/osw/streamstats/
Climatic caveats:
• Unchanging mean annual precipitation
• Seasonality is lost in calculation
Climate Change Scenarios for the PNW
Figures’ source: Mote and Salathé 2010
Temperatures warm across all projections
Mean annual precipitation projections do not show a clear trend
Seasonal signal of precipitation shifts is lost in the annual projections
Contrasting Hydrologic Models
Physically-based VIC Model
Explicitly integrates climate conditions
Applies future T & P projections to estimate daily runoff at each grid cell
Daily runoff used to estimate shifts in extreme streamflowfrequency
Spatial resolution:
Fine - 1/16th °Aggregate - 12 digit
HUCs
USGS Regression-based model
Regressions applied based on region
Historical and future P from climate models
USGS VIC
Comparing Results
Shows increases in annual precipitation only
No response to warmer temperatures or the changing seasonality of precipitation
Captures the temporal and spatial variability in the climate models
Responds to future warming and increases in winter precipitation with a rise in flood severity
Difference of Sensitivity
Shift in Flood Severity
1/16th degree 12-digit HUCs
Comparing the Future to Historical 100-Year Flood – 2040s
Map: Rob Norheim
Shift in Low Flow SeverityComparing the Future to Historical 7Q10 – 2040s
1/16th degree 12-digit HUCs
Map: Rob Norheim
Summary Statistics: Low Flow
Summary Statistics: Flood
Future Applications
Implement extreme streamflow analysis over PNW domain
Assess changes in risk to fish habitat and infrastructure in other National Forests/Parks:
North Cascades
Mt Baker/Snoqualmie
Mt Rainier