Forecasting Streamflow with the UW Hydrometeorological Forecast System

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Forecasting Streamflow with the UW
Hydrometeorological Forecast System
Ed Maurer Department of Atmospheric Sciences,
University of Washington Pacific Northwest
Weather Workshop March 8, 2003
Photos from www.metrokc.gov
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UW Hydromet System and Water Resource Time Scales
Weather floods, drainage, operations Seasonal/In
terannual water supply planning,
droughts Climate climate change, urbanization
Ref A Plan for a New Science Initiativeon the
Global Water Cycle, www.usgcrp.gov
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Temporal and Spatial Scales of Hydrologic
Variability
Ref A Plan for a New Science Initiativeon the
Global Water Cycle, www.usgcrp.gov
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MM5-DHSVM Streamflow Forecast System
UW Real-time MM5
DHSVM
Distributed-Hydrology-Soil-Vegetation Model
Completely automated In use since WY 1998 For
details Westrick, K.J., P. Storck, and C.F.
Mass, Description and Evaluation of a
Hydrometeorological Forecast System for
Mountainous Watersheds, Weather and Forecasting
17 250-262, 2002.
Streamflow and other forecasts
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Penn State/NCAR Mesoscale Model MM5
Used throughout the world for both research and
operational forecasting 48-hour (and some 72-hour
and longer) forecasts run twice daily at the
University of Washington High-resolution model
(4-km) capable of capturing the complex orography
of the region, including lee shading and windward
precipitation enhancement
FOR MORE INFO...
http//www.atmos.washington.edu/mm5rt/
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DHSVM land surface hydrology model

• Physically-based, distributed model
• Solves a water balance at each grid cell at each
  time step
• Horizontal scales typically 30m to 150m
• Designed for and extensively tested in complex
  terrain

Details on DHSVM at http//www.hydro.washington.e
du/
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DHSVM Calibration

• Calibration at 2 sites in Snohomish River Basin
• Used all available meteorological observations
  (50sites), 1987-1991
• Used flow observations at two USGS gauges
• Skykomish R. near Gold Bar
• Snoqualmie R. at Carnation

Snoqualmie R. at Carnation
Peaks flows and average water balance are well
simulated by DHSVM when forced by observed
meteorology
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UW Hydromet Domain - 2003
26 basins 60 USGS Gauge Locations 48,896
km2 2,173,155 pixels DHSVM _at_ 150 m
resolution MM5 _at_ 4 12 km
http//hydromet.atmos.washington.edu
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Web Site for Forecast Dissemination

• Automatically updated twice daily
• Graphic display indicates forecasted flood status
• Click through to
• Hydrographs
• Snow state (maps and points)
• Point weather forecasts

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Performance of Hydromet System
Sauk
Snoqualmie
Observed
MM5-DHSVM
NWRFC
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Using the Hydromet system for MM5 diagnosis

• One exceptionally bad forecast for the Cedar R.,
  events from January 25 to Feb 4, 2003
• Second peak
• Forecast1200 cfs
• Observed 3700 cfs
• Flood stages above bankfull occurred, and were
  not forecast

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Representative Meteorological Station Mt.
Gardner
Avg. Precipitation from 1/24 - 2/7 Observed 1.0
mm/h Simulated 0.7 mm/h Total difference 100 mm
Precip
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Opportunity for Improving UW Hydromet Forecasts
1 Precipitation/Temperature Bias
Correction Remove systematic biases in P, T, at
land surface 2 IMPROVE-2 Take advantage of the
IMPROVE-2 experiment to examine the interplay
between observation density and bias correction
performance 3 Initial State Updating
Assimilation of snow and soil moisture
information from an observationally constrained
data set.
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Snow State Updating with Observations
Use ground observations (SNOTEL sites) to adjust
the basin snow state
Challenge 45-50 snow water observations for
48,000 km2 domain low density places high
dependence on interpolation assumptions
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Expansion of Forecast Products
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Summary

• UW Hydrometeorological Forecast System provides
  accurate streamflow and snowpack predictions when
  forced with accurate meteorology and when
  properly initialized
• Improvements in both initialization and
  meteorological forecasts are ongoing, by
  analyzing current flood events and retrospective
  analysis
• The capabilities of the system are being expanded
  to include both probabilistic forecasts using
  ensembles, and to include landslide hazard
  evaluation

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Acknowledgments
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Current Streamflow Forecasts

• NWRFC provides river flow and stage forecasts at
  strategic points in Puget Sound region
• Use point forecasts of precipitation and
  temperature
• Streamflow produced by a lumped parameter
  hydrologic model (does not produce spatially
  distributed water balance estimates)

www.nwrfc.noaa.gov
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Original Motivation for Developing UW Hydromet
System

• Integrated modeling over a variety of spatial and
  temporal scales to examine
• Regionally consistent modeling of weather and
  land surface hydrology, avoid site-specific
  calibration
• Capture topographically-driven spatial variation
  in precipitation, temperature, and wind fields
• Produce experimental streamflow forecasts to
  investigate skill in a coupled model setting
• Use hydrometeorological forecasts as a diagnostic
  tool for mesoscale atmospheric model