mid-range water supply forecasts for municipal water supplies matthew wiley, richard palmer, and...
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Mid-Range Water Supply Forecasts for Municipal Water Supplies
Matthew Wiley, Richard Palmer, and Michael
Miller
Department of Civil and Environmental Engineering
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Today’s Presentation Need for forecast Describe approach Present forecasts Introduce Website
www.tag.washington.edu
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Goals Evaluate the value of a 6-month
meteorological forecast in making water resources decisions
Use meteorological forecast to create a forecast of streamflows Evaluate the meteorological data Evaluate the hydrologic response
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Seattle Public Utilities
Tacoma Water
Everett Public Utilities
Partner Utilities
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Problem Setting Project Setting – Puget Sound
Region Water supply to 2.6 million Flood Control Navigation Hydropower Environmental
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Water Supply Utility Challenges Provide safe, reliable and inexpensive
drinking water Preserve environmental quality,
demonstrate resource stewardship Maintain/enhance Infrastructure Provide stable and economically viable
rate structure Adapt to evolving water quality
requirements
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Primary Purposes of Forecast Refill decisions in spring Supply evaluation in early summer Decisions related to fish flows
(when is water most needed) Curtailment decisions in late
summer Drawdown decisions in fall
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Value of Forecast Utility has established operating
policies Forecast is valuable if it provides
information that modifies policy and forecast is correct
Accurate forecasts of normal, below, or above normal are desired (can result in policy change)
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Approaches
Historical Streamflows Assume averages are sufficient
Ensemble Streamflow Predictions (ESP) Well-established approach Used by Weather Service Can be conditioned on climate
condition
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ESP Forecast
obs
Recently ObservedMeteorological Data
Ensemble of Meteorological
Data to Generate forecast
ICsSpin-up Forecast
hydrologicstate
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Approaches
National Centers for Environmental Prediction (NCEP) 6-month forecasts Uses Global Climate Model to produce
forecast ensembles Can be compared to ESP
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National Centers for Environmental Prediction (NCEP) climate forecast.
Initial and PredictedSST for next6 months
20 differentInitial statesof the atmosphere
20 unique forecasts of the climate over the next six months
We use the raw model output at this point.
2x2 degree GSMCoupled Ocean-AGCM
OfficialNCEP ClimateForecast
Correlation AnalysisPast ExperienceProbability Mapping
20 Ensemble Forecast
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National Centers for Environmental Prediction (NCEP) climate forecast.
Initial and PredictedSST for6 months
10 differentinitial states that existedof the atmosphere
10 unique hindcasts of the climate for each year over the next six months
We use Hindcasts for bias correction and retrospective analysis
2x2 degree GSM
Coupled Ocean-AGCM
OfficialNCEP ClimateForecast (210 hindcasts)
Used in conjunction with forecasts for bias correction
10 Ensemble Hindcasts
Years
1979
1980
1981
1999
Years
1979
1980
1981
1999
21 year
s
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Forecasts being produced
ESP NCEP http://www.tag.washington.edu/
projects.html
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South Fork Tolt River, August 2004, Unconditioned ESP
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South Fork Tolt River, August 2004, ENSO based ESP
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Tentative Conclusions Streamflow Forecast
In small west slope basins, NCEP is generally more useful than ESP
Monthly forecast Poor in December Better in later months of the forecast
Seasonal Forecast Better in the spring and early summer Poor in late winter
NCEP is in the process of revising its mid-range forecasting procedures
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Future Work continues
Water Temperature Modeling Improve Web Viewing Continue With Forecasts Additional Evaluation of the Quality of
the Forecast Conditional evaluations Evaluate other types of Forecasts IRI, CPC
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Stream Temperature Forecasts
Conditions at USGS 12147600, South Fork Tolt River, above S.F.T. Reservoir
0
200
400
600
800
1000
1200
1400
09-2
002
10-2
002
11-2
002
12-2
002
01-2
003
02-2
003
03-2
003
04-2
003
05-2
003
06-2
003
07-2
003
08-2
003
09-2
003
10-2
003
11-2
003
12-2
003
01-2
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02-2
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03-2
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04-2
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CF
S
012345678910111213141516
deg
rees
C
Observed Temperature
Observed Flow
Simulated Temperature
Simulated Flow
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Stream Temperature Forecasts
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Future Work continues
Water Temperature Modeling Improve Web Viewing Continue With Forecasts Further Evaluation of Forecast Quality Consider other climate forecasts: IRI, CPC Additional Water Supply Basins
White River Bull Run Tualatin
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Web Page
http://www.tag.washington.edu Projects
Mid-Range Forecasts
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