Medium-range Hydrometeorological Forecasts of the Big Wood Basin in 2006 (plus a look forward at 2007…) A Project for the Pacific Northwest Regional Collaboratory

Contributors University of Idaho, Dept. of Geography: Troy R. Blandford, M.S. in 2006 Brian J. Harshburger, PhD Candidate Karen S. Humes, Associate Professor Brandon C. Moore, M.S. in 2006 Von P. Walden, Associate Professor Idaho National Laboratory (INL): Ryan Hruska, Senior Engineer/Scientist

Snowmelt Runoff Model SRM is a semi-distributed, temperature index (degree-day) model designed to simulate and forecast streamflow in snowmelt-dominated (mountainous) basins. –Model inputs: Current temperature and precipitation from SNOTEL sites Snow-covered Area –Derived from MODIS images »INL (Ryan Hruska) »NSIDC (Tom Painter) Forecasted Temperatures –Medium-range, 15-day from NCEP GFS (downscaled to SNOTEL sites) –Short-range, 7-day from NDFD (4 day - precipitation) –Temporal resolution: daily

Downscaling of Met Forecasts Example of downscaling of four NCEP Global Forecasting System (GFS) grid points (large yellow dots) to individual SNOTEL station locations (small black dots) Clark and Hay, (2004)

Errors in NCEP and NDFD Temperatures Moore et al., 2006

SRM Enhancements The use of both maximum and minimum critical temperatures (Tcrit max and Tcrit min ) to partition precipitation into rain, snow, and rain/snow mixed. –model currently uses a single critical temperature value The use of an antecedent temperature index (ATI) method to track snowpack cold-content and account for the delay in melt associated with diurnal refreezing. –used to determine when the snowpack is ripe –also to determine when the rain falling on the snowpack should contribute to the runoff

SRM Enhancements 15 Day Downscaled Temperature Forecasts (T max, T min ) Global Forecasting System NCEP Enhanced version of SRM 15 Day Downscaled Precipitation Forecasts Global Forecasting System NCEP Observed Temperature (T max, T min ) SNOTEL, NRCS Obtained 1 day after measured Observed Precipitation SNOTEL, NRCS Obtained 1 day after measured Observed Streamflow USGS Obtained 1 day after measured Forecasted Inputs Model Updating (Day n-1) Model Parameters (Retrospective Analysis) Snow Depth and SWE observations SNOTEL, NRCS (monitor degree-day factors) Snow-covered Area (SCA) (Obtained from snow depletion curves) Ensemble Streamflow Forecasts Schaake Shuffle (reorder the ensembles) Ensemble Streamflow Forecasts

Study Area for 2006 Big Wood River Basin Stream Gauge: Hailey, ID Contributing Area: 1,625 km 2 Elevation Range: 250-3,630 m location of SNOTEL sites

Retrospective Forecast Results (2002) Coefficient of Determination (R 2 ) Mean Bias Error (cms) Mean Absolute Error (cms)

Retrospective Forecast Results (2003) Coefficient of Determination (R 2 ) Mean Bias Error (cm) Mean Absolute Error (cm)

Retrospective Forecast Results (2004) Coefficient of Determination (R 2 ) Mean Bias Error (cm) Mean Absolute Error (cm)

Real-time Forecasting in 2006

SRM correctly forecasted the timing of the peak discharge (May 22, 2006) out 6 days in advance. –Early by 1 day at a lead time of 7 days and 2 days at 10 days The magnitude of the peak was slightly under-predicted for all of the lead-times illustrated here. The forecasts of the secondary peak, which occurred in early June, require further investigation and may be due to errors in the input data (i.e. snow covered area). The timing of the forecasts are off (timing of smaller peaks) during the early and late portions of the snowmelt season. –May be due to time lag between snowmelt and precipitation events and the resulting stream discharge

Create a decision support system for interested parties that is –Easy to use –Accurate Intention is to create tools for many basins, not just a single basin, for end-users (NRCS, COE) –UI training session on basin disaggregation and how to process snow-cover images (snow-covered area) Preparation for 2007

Automation - Improved tools for ArcGIS

ArcGIS Tools

Preparation for 2007 Automation - Improved tools for ArcGIS Additional basins

North Fork of the Clearwater St. Joe River Big Lost River Little Wood River Fisher River (Montana) South Fork of the Flathead (Montana) And perhaps basins in Washington and Oregon as well Potential New Basins for FY07

Preparation for 2007 Automation - Improved tools for ArcGIS Additional basins Ensemble and Single-value (like 2006) forecasting Downscaling of global climate model output for simulation of future stream flow conditions in the PNW