Transcript NWRFC mission/pupose - University of Washington

Seasonal Volume Forecasts
Using Ensemble Streamflow Prediction
for the 2007 Water Year
Steve King, Hydrologist
Northwest River Forecast Center
Topics for Presentation
 Northwest River Forecast Center:
 Overview
 NWRFC Long Range Forecasting Models and Products
 Statistical Water Supply Forecasts
 Ensemble Streamflow Prediction (ESP)
 Recap of WY 2006 Forecasts
 2007 Volumetric Streamflow Outlook
 New Web Tools for Users
Northwest River Forecast Center
Total Area: 315,795 Columbia and
Snake River
Basins
Grand Coulee Dam
Lower Granite Dam
The Dalles Dam
Coastal Drainages
of Oregon and
Washington
6 States &
CANADA
The Willamette at Salem
Support for
9 NWS Field
Offices (WFOs)
NWRFC Forecasting Models
 Statistical Water Supply
 Seasonal Volumetric Forecasts
• Regression techniques
 NWS River Forecast System
 Short, Medium, and Longterm capabilities
• Generates output in deterministic AND probabilistic (ESP) formats
• Variable Outputs for ESP
• Adjusted Flow: similar to regression-based Water Supply (147 points)
• Natural Streamflow (302 NWSRFS forecast points)
• CPC Climate Adjusted
Statistical Water Suppy
Combined Index:
Observed Precip
Observed Snow
Observed Runoff
Future Precip
NWS River Forecast System
Model Components (simplified)
Snow Model
Soil Moisture/Runoff
Consumptive Use
River Routing
Reservoir Regulation
Flow and Stage
Forecasts
Rain Plus Snow Melt
ESP
Example showing 42 traces outcomes for
The Columbia River at The Dalles, OR
Traces represent ensemble of possible
river flow behavior (Jan-Jul)
Exceedance probability plot
of flow volumes = area under each trace
(Jan-Jul period)
50% Value (most expected)
is comparable to WS forecasts
Median Forecast
(most expected)
Volume Forecasts Available at
www.nwrfc.noaa.gov
Statistical Water Supply
ESP Volume Forecasts
2006 WS Forecast Recap
(Jan-Jul ‘06)
Jan-Jul Volume
30 yr Normal 51 MAF
Jan-Jul Volume
Forecasts
2006 Jan-Jul Cumulative
Obs Volume 54 MAF – 106%
2006 WS Forecast Recap
(Jan-Jul ‘06)
Jan-Jul Volume
30 yr Normal 107 MAF
Jan-Jul Volume
Forecast
2006 Jan-Jul Cumulative
ObsVolume 115 MAF – 107%
Spring Outlook - 2007
 Ensemble Streamflow Prediction (ESP)
 Adjusted Volume Forecasts Issued for Statistical
Water Supply Points (147)
 Natural Volume Forecast for all NWSRFS Points (302)
 Updated weekly
 Driven by:
Antecedent Snow/Soil Moisture
10 day Precip and Temp Forecast
 Soon to incorporate climate forecasts
2007 Outlook (ESP Forecasts)
96 % of Normal (63 MAF)
96 % of Normal (107 MAF)
Taking Advantage of Climate
Forecasts:

ESP Pre Adjustment Technique:

CPC Outlooks are used to shift distribution
of model inputs (temperature and precipitation)
CPC vs Non-CPC ESP Forecast
Dworshak Reservoir Inflow Example
Standard
ESP Forecast
2007
Median = 3.44 KAF
CPC Adjusted
ESP Forecast
Median = 3.22 KAF
30yr Norm = 3.55 KAF
ESP Products
“Natural” Streamflow Forecasts
ESP “Water Supply”
Forecast Locations
ESP “Natural”
Forecast Locations
New Web Tool
New Volumetric Forecast Display Tool
New Web Tool
New Web Tool
New Web Tool
New Web Tool
Northwest River Forecast Center
www.nwrfc.noaa.gov