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Mid-Range Water Supply Forecasts for Municipal Water Supplies

Mid-Range Water Supply Forecasts for Municipal Water Supplies . Matthew Wiley, Richard Palmer, and Michael Miller Department of Civil and Environmental Engineering. Today’s Presentation. Need for forecast Describe approach Present forecasts Introduce Website www.tag.washington.edu.

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Mid-Range Water Supply Forecasts for Municipal Water Supplies

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  1. Mid-Range Water Supply Forecasts for Municipal Water Supplies Matthew Wiley, Richard Palmer, and Michael Miller Department of Civil and Environmental Engineering

  2. Today’s Presentation • Need for forecast • Describe approach • Present forecasts • Introduce Website • www.tag.washington.edu

  3. 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

  4. Partner Utilities Seattle Public Utilities Tacoma Water Everett Public Utilities

  5. Problem Setting • Project Setting – Puget Sound Region • Water supply to 2.6 million • Flood Control • Navigation • Hydropower • Environmental

  6. 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

  7. 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

  8. 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)

  9. Approaches • Historical Streamflows • Assume averages are sufficient • Ensemble Streamflow Predictions (ESP) • Well-established approach • Used by Weather Service • Can be conditioned on climate condition

  10. ESP Forecast Ensemble of Meteorological Data to Generate forecast Recently Observed Meteorological Data Spin-up ICs Forecast hydrologic state obs

  11. Approaches • National Centers for Environmental Prediction (NCEP) 6-month forecasts • Uses Global Climate Model to produce forecast ensembles • Can be compared to ESP

  12. National Centers for Environmental Prediction (NCEP) climate forecast. 20 Ensemble Forecast Coupled Ocean-AGCM 2x2 degree GSM 20 different Initial states of the atmosphere Official NCEP Climate Forecast 20 unique forecasts of the climate over the next six months Initial and Predicted SST for next 6 months Correlation Analysis Past Experience Probability Mapping We use the raw model output at this point.

  13. Years 1979 1980 1981 1999 National Centers for Environmental Prediction (NCEP) climate forecast. 10 Ensemble Hindcasts 2x2 degree GSM 10 unique hindcasts of the climate for each year over the next six months 10 different initial states that existed of the atmosphere Coupled Ocean-AGCM Official NCEP Climate Forecast (210 hindcasts) Initial and Predicted SST for 6 months Years 1979 1980 1981 1999 Used in conjunction with forecasts for bias correction 21 years We use Hindcasts for bias correction and retrospective analysis

  14. Forecasts being produced • ESP • NCEP • http://www.tag.washington.edu/projects.html

  15. South Fork Tolt River, August 2004, Unconditioned ESP

  16. South Fork Tolt River, August 2004, ENSO based ESP

  17. 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

  18. 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

  19. Stream Temperature Forecasts

  20. Stream Temperature Forecasts

  21. 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

  22. Web Page • http://www.tag.washington.edu • Projects • Mid-Range Forecasts

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