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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

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Presentation Transcript
slide1

Seasonal Volume Forecasts

Using Ensemble Streamflow Prediction

for the 2007 Water Year

Steve King, Hydrologist

Northwest River Forecast Center

topics for presentation
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
slide3

Northwest River Forecast Center

Total Area: 315,795

Columbia and

Snake River

Basins

Coastal Drainages of Oregon and Washington

6 States &

CANADA

Support for

9 NWS Field Offices (WFOs)

Grand Coulee Dam

Lower Granite Dam

The Dalles Dam

The Willamette at Salem

nwrfc forecasting models
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
Statistical Water Suppy

Combined Index:

Observed Precip

Observed Snow

Observed Runoff

Future Precip

nws river forecast system model components simplified

Rain Plus Snow Melt

NWS River Forecast System Model Components (simplified)

Snow Model

Soil Moisture/Runoff

Consumptive Use

River Routing

Reservoir Regulation

Flow and Stage

Forecasts

slide7

Median Forecast

(most expected)

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

volume forecasts available at www nwrfc noaa gov
Volume Forecasts Available at www.nwrfc.noaa.gov

ESP Volume Forecasts

Statistical Water Supply

slide9

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)

slide10

Jan-Jul Volume

30 yr Normal 107 MAF

Jan-Jul Volume

Forecast

2006 Jan-Jul Cumulative ObsVolume 115 MAF – 107%

2006 WS Forecast Recap(Jan-Jul ‘06)

spring outlook 2007
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
slide12

2007 Outlook (ESP Forecasts)

96 % of Normal (63 MAF)

96 % of Normal (107 MAF)

slide13

Taking Advantage of Climate Forecasts:

  • ESP Pre Adjustment Technique:
    • CPC Outlooks are used to shift distribution

of model inputs (temperature and precipitation)

slide14

Standard

ESP Forecast

Median = 3.44 KAF

CPC Adjusted

ESP Forecast

Median = 3.22 KAF

30yr Norm = 3.55 KAF

2007

CPC vs Non-CPC ESP ForecastDworshak Reservoir Inflow Example

slide15

ESP “Water Supply”

Forecast Locations

ESP “Natural”

Forecast Locations

ESP Products

“Natural” Streamflow Forecasts