Modeling Hydrological Processes Ed Maurer PRISM Science Retreat Friday, September 27, 2002

Acknowledgments

Hydrological Modeling Hydromet System – provides a valuable regional research tool. Maintenance Improvement Expansion

MM5-DHSVM Streamflow Forecast System UW Real-time MM5 Distributed-Hydrology-Soil- Vegetation Model Completely automated In use since WY 1998 DHSVM Streamflow and other forecasts

Summary of Hydromet System Real-time Streamflow Forecast System 26 basins ~60 USGS Gauge Locations 48,896 km2 2,173,155 pixels DHSVM @ 150 m resolution MM5 @ 4 & 12 km http://hydromet.atmos.washington.edu

Some Recent Publications 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. Mass, C.F., D. Ovens, K. Westrick, and B.A. Colle, Does Increasing Horizontal Resolution Produce More Skillful Forecasts?. Bull. Amer. Meteorol. Soc. 83: 407-430, 2002. Westrick, K.J. and C.F. Mass, An Evaluation of a High-Resolution Hydrometeorological Modeling System for Prediction of a Cool-Season Flood Event in a Coastal Mountainous Watershed, J. Hydrometeorology 2: 161-180, 2001.

Maintenance of System As models evolve and data formats change, the system must adapt Data format for streamflow observations Extending forecasts to 48 hours as with 4 km MM5

Performance of Hydromet System Sauk Snoqualmie Observed MM5-DHSVM NWRFC

Hydromet Performance 2 Deschutes Nisqually MM5-DHSVM Observed NWRFC These comparisons stressed the importance of accurate precipitation forecasts NWRFC

Summary of Performance Sauk Skykomish N.Fork Snoq M.Fork Snoq. Snoqualmie Cedar Average Relative Error in Peak Flow Forecast Obs-based Control No Bias NWRFC Results from 6 events – Westrick et al., 2002 Best forecasts w/obs., avg. error 31% Not significantly better than control or RFC

Opportunity for Improving Hydromet Forecasts One key finding from Westrick et al., 2002: Precipitation uncertainties in observed data due to: Instrument error Areal representativeness of point obs. Interpolation method These errors can be nearly as large as uncertainty in meteorological forecast. This applies at least to the 13-24 hour forecast.

Lack of Observations To improve forecasts, we must identify the relative magnitudes of the errors. Precipitation observations at a spatial resolution sufficient to determine “reality” do not exist in domain IMPROVE – 2 study provides a valuable context for examining the orographic precipitation for several events, and provides a basis for intercomparing the errors

IMPROVE-2 Orographic Precipitation Study Nov-Dec 2001 Raingauges Snotel Co-op Observer Radar Disdrometer

Expansion of Forecasting Tools DHSVM produces more than just streamflow Soil moistures, slopes in model provide additional forecasting capabilities Investigate landslide hazard forecasting

DHSVM Sediment Production and Transport SURFACE EROSION CHANNEL EROSION MASS WASTING Watershed Sediment Module

DHSVM Structure Modifications DEM Met. data Vegetation (type, LAI, height) Soil texture Soil depth f(Soil Cohesion) f(Veg. Cohesion) Soil moisture Overland flow Channel flow

Mass Wasting Module Multiple realizations of total failure locations Multiple time series of sediment supply MASS WASTING Factor of Safety

Summary Many Opportunities to Build on the Past Successes Coordination with Others in the PRISM Community is an Essential Component