Seasonal Volume ForecastsSeasonal Volume ForecastsUsing Ensemble Streamflow PredictionUsing Ensemble Streamflow Prediction

for the 2007 Water Yearfor the 2007 Water Year

Kevin Berghoff, HydrologistNorthwest River Forecast Center

Topics for Presentation

Northwest River Forecast Center:Northwest River Forecast Center: OverviewOverview

NWRFC Long Range Forecasting Models and ProductsNWRFC Long Range Forecasting Models and Products Statistical Water Supply ForecastsStatistical Water Supply Forecasts Ensemble Streamflow Prediction (ESP)Ensemble Streamflow Prediction (ESP)

Recap of WY 2006 Forecasts Recap of WY 2006 Forecasts 2007 Volumetric Streamflow Outlook2007 Volumetric Streamflow Outlook New Web Tools for UsersNew Web Tools for Users

Northwest River Forecast CenterNorthwest River Forecast Center

Total Area: 315,795

Grand Coulee Dam

The Willamette at Salem

The Dalles Dam

Lower Granite Dam

Columbia and Columbia and Snake River Snake River BasinsBasins

Coastal Drainages Coastal Drainages of Oregon and of Oregon and WashingtonWashington

6 States & 6 States & CANADACANADA

Support forSupport for9 NWS Field 9 NWS Field Offices (WFOs)Offices (WFOs)

NWRFC Forecasting Models

NWS River Forecast SystemNWS River Forecast System Short, Medium, and Longterm capabilities Short, Medium, and Longterm capabilities

• Generates output in deterministic Generates output in deterministic ANDAND probabilistic (ESP) formats probabilistic (ESP) formats• Variable Outputs for ESPVariable Outputs for ESP

• Adjusted Flow: similar to regression-based Water Supply (147 points)Adjusted Flow: similar to regression-based Water Supply (147 points)• Natural Streamflow (302 NWSRFS forecast points)Natural Streamflow (302 NWSRFS forecast points)• CPC Climate AdjustedCPC Climate Adjusted

Statistical Water Supply Statistical Water Supply Seasonal Volumetric ForecastsSeasonal Volumetric Forecasts

• Regression techniquesRegression techniques

Statistical Water SupplyStatistical Water Supply

Combined Index:

Observed Precip Observed Snow Observed Runoff

Future Precip

Snow ModelSnow Model

Soil Moisture/RunoffSoil Moisture/Runoff

Consumptive UseConsumptive Use

River Routing River Routing

Reservoir RegulationReservoir Regulation

Flow and Stage Flow and Stage ForecastsForecasts

NWS River Forecast System NWS River Forecast System Model Components (simplified)Model Components (simplified)

Rain Plus Snow Melt

Exceedance probability plotof flow volumes = area under each trace (Jan-Jul period)

50% Value (most expected)is comparable to WS forecasts

Example showing 42 traces outcomes for The Columbia River at The Dalles, OR

Traces represent ensemble of possible river flow behavior (Jan-Jul)

Median Forecast(most expected)

ESP

Volume Forecasts Available at Volume Forecasts Available at www.nwrfc.noaa.govwww.nwrfc.noaa.gov

Statistical Water Supply ESP Volume Forecasts

2006 WS Forecast Recap

Jan-Jul Volume Forecasts

30 yr Normal 63 MAF

2006 Obs Volume 69 MAF – 106%

Jan-Jul Volume

Forecast

30 yr Normal 107 MAF

2006 Obs Volume 115 MAF – 107%

30 yr Normal 3.55 MAF

2006 Obs volume 3.5 MAF – 99%

Jan-Jul Volume Forecasts

Jan-Jul Volume Forecasts

2006 Obs Volume 32.2 MAF – 107%

30 yr Normal 30 MAF

Oct 06 ESP FX 3.5 MAF – 99%

Oct 06 ESP FX 63.8 MAF – 101%

Oct 2006 ESP FX

26.7 MAF – 89%Oct 06 ESP FX 26.7 MAF – 89%

Oct 06 ESP FX 98.5 MAF – 92%

2006 ESP/Regression WS 2006 ESP/Regression WS ComparisonComparison

ESP/Regression WS ComparisonDworshak Dam

2006 Jan-Jul Volume - kaf

2000

2500

3000

3500

4000

4500

Jan Feb Mar Apr May

ESP Regression WS

2006 Jan-Jul Observed Volume = 3507 kaf (99%)

Spring Outlook - 2007Spring Outlook - 2007

Ensemble Streamflow Prediction (ESP)Ensemble Streamflow Prediction (ESP) Adjusted Volume Forecasts Issued for Statistical Adjusted Volume Forecasts Issued for Statistical

Water Supply Points (147)Water Supply Points (147) Natural Volume Forecast for all NWSRFS Points (302)Natural Volume Forecast for all NWSRFS Points (302)

Updated weeklyUpdated weekly

Driven by: Driven by: Antecedent Snow/Soil MoistureAntecedent Snow/Soil Moisture 10 day Precip and Temp Forecast10 day Precip and Temp Forecast

Also incorporating CPC climate forecastsAlso incorporating CPC climate forecasts

2007 Outlook – ESP Forecast2007 Outlook – ESP Forecast

3351 KAF-94% 57412 KAF-91%

29470 KAF-98%98130 KAF - 91%

Climate DiscussionsClimate Discussions

CPC ENSO Discussion – Oct 5, 2006 CPC ENSO Discussion – Oct 5, 2006 ……Typical El Nino conditions are likely to develop over North America during Typical El Nino conditions are likely to develop over North America during

the coming winter season…warmer than average temperatures over western the coming winter season…warmer than average temperatures over western and northern U.S. … drier than average conditions in the PNW…and northern U.S. … drier than average conditions in the PNW…

UW Climate Impacts Group – Sep 13, 2006UW Climate Impacts Group – Sep 13, 2006 ……Weak El Nino conditions are likely to continue, and possibly intensify, into Weak El Nino conditions are likely to continue, and possibly intensify, into

early 2007…early 2007…

International Research Institute for Climate Prediction – Sept 20, 2006International Research Institute for Climate Prediction – Sept 20, 2006 ……thresholds for El Nino conditions (SST anomolies) have been crossed thresholds for El Nino conditions (SST anomolies) have been crossed

recently…probability of developing El Nino conditions is 55-60% by the end recently…probability of developing El Nino conditions is 55-60% by the end of 2006…and that of maintaining neutral conditions is approximately 40%... of 2006…and that of maintaining neutral conditions is approximately 40%...

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

of model inputs (temperature and precipitation)of model inputs (temperature and precipitation)

Taking Advantage of Climate Taking Advantage of Climate Forecasts: Forecasts:

CPC vs Non-CPC ESP ForecastDworshak Reservoir Inflow Example

2007

CPC vs non-CPC ESP ForecastCPC vs non-CPC ESP ForecastJan – Jul Volume ComparisonJan – Jul Volume Comparison

Jan-Jul 30 Yr Jan-Jul 30 Yr Normal-kafNormal-kaf

Std. ESP Std. ESP

(% Normal)(% Normal)

CPC adj ESP CPC adj ESP

(% Normal)(% Normal)

% Diff% Diff

DworshakDworshak 35473547 3350 (94%)3350 (94%) 3170 (89%)3170 (89%) -5.3%-5.3%

Lower Granite Lower Granite 3001630016 29500 (98%)29500 (98%) 28700 (96%)28700 (96%) -2.0%-2.0%

Grand Coulee Grand Coulee 6289962899 57400 (91%)57400 (91%) 56000 (89%)56000 (89%) -2.5%-2.5%

DallesDalles 107302107302 98100 (91%)98100 (91%) 95800 (89%)95800 (89%) -2.3%-2.3%

ESP Products ESP Products ““Natural” Streamflow ForecastsNatural” 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 CenterNorthwest River Forecast Center

www.nwrfc.noaa.govwww.nwrfc.noaa.gov