PUM A Workshop December 1, 2010 San Francisco, CA Water Utility M odeling at Seattle Public Utilities Paul Fleming M anager, Climate and Sustainability Group Joan Kersnar M anager, Drinking Water Planning Seattle Public Utilities
Outline • Seattle context • SPU’s Climate Program • Chain of M odels • Water Supply M odeling • Hydrologic M odeling • Conclusion
Hydrologic and Physical Context Sequim – 17” Seattle – 37” Cedar River Watershed – 100” Hoh River Valley - 150-180”
Operating Context • Seattle Public Utilities Department of City of Seattle o Part of Executive Branch o Budget/ rates approved by City Council o Federal statutory requirements o • 1.4 million retail and wholesale customers • ~ 1400 employees Water M anagement responsible for modeling, system operations o Long Term Planning responsible for planning o Climate and Sustainability responsible for climate issue o
Seattle’s Water Supply System • Responsibilities: Water supply for people o o Instream flows for salmon habitat in perpetuity o Flood management o Hyrdopower generation o Land management • M ountain-based surface water supplies, nominal groundwater • Cedar storage – 19% of annual flow; Tolt 49% • Largest supply is unfiltered • Rely on snowpack and rain, may be more dependent on rain than snow
Seattle’s Water Supply Outlook Average Daily Demand: 2009: 130 mgd 2060: 159 mgd Available Supply: 171 mgd can be diverted after meeting instream flows
Growth in Population and Water Consumption Seattle Regional Water System: 1975-2007 1,400,000 280 1,300,000 260 1,200,000 240 Population 1,100,000 220 1,000,000 200 900,000 Total Consumption 180 800,000 160 Non-Revenue 700,000 140 600,000 120 500,000 100 Billed Consumption 400,000 80 300,000 60 Since the peak in 1984, total consumption has 200,000 40 fallen 27% while population has grown by 25%. 100,000 20 0 0 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
Adaptation and M itigation • Adaptation Identifying impacts o Pursuing “ no regrets” options o Enhancing our knowledge o Building internal capacity o Collaborating o • M itigation Finalizing GHG inventory o Assessing potential for climate neutrality o
Engagement and Collaboration
Challenges and Issues • Projecting climate impacts on supply Effects on snowpack – timing and quantity o Changes in precipitation o Return of fall rains o • Projecting climate impacts on quality Extreme events o Frequency and extent of forest fires o • ENSO/ PDO • Co-production of knowledge • Incorporating climate signal into decision-making
Data, M onitoring and Forecasts • Real time forecasting and monitoring info is essential • Utilize several federal agency sources USGS stream gages o USDA/ NRCS SnoT el sites o NOAA/ NWS daily and mid range weather forecasts o NOAA’s Climate Prediction Center 30-90 day outlooks o NOAA/ NASA remote sensing of snowpack o • Applications Inform short term operational needs and longer term planning o horizons Compliance with instream flows o Inform reservoir management and releases o Project water supply availability o
Chain of M odels Down- Utility S ystem Hydrology GCM Planning scaling M odel
Utility M odeling • Historic Inflows • New Source System Water • Firm Yield • Gaged Flows Decisions Hydrology M odel: Utility • Calculated • Simulation • Capital CUE Planning Results • Reconstructed Programs from • Negotiations correlations • Precip • Seasonal • Snow (SWE) operating plan • Air temp • Inflows / M et Water Hydrology: (refill, • Pan evap Streamflows Station Utility instream SEAFM Data • Solar Planning • Reservoir flows, etc.) radiation Levels • Flood • Wind operating
Conjunctive Use Evaluation (CUE) M odel • Simulates reservoir and river operations at weekly timestep • M odels entire system - Cedar, SF T olt, Lake Y oungs (optional) • Historic Inflows System • Firm Yield Programmed in Stella to • Gaged Flows o M odel: Hydrology • Simulation • Calculated CUE enable users to set Results • Reconstructed from operating rules correlations • Uses historic inflow data Reconstructed 81 years, o starting in 1929 Can also use other inputs o • Provides SPU with insights about system performance and vulnerabilities
Water System M odel Uses • Estimating firm yield • Optimizing use of multiple sources, maximizing of existing • New Source • Determining yield from new supply System Water Decisions • Firm Yield alternatives, impacts on reservoir • Capital M odel: • Simulation Utility Programs Results CUE Planning levels and streamflows • Negotiations • Impacts of long term flood management operations • Evaluating instream flow regime proposals • Establishing management triggers • Determining frequency of critical operations • Assessing climate impacts to all of the above
Seattle’s Hydrology M odel - SEAFM • Continuous watershed simulation model with hourly timestep Based on HSPF o Also using HFAM o • Driven by met data from nearby • Precip • Snow (SWE) • Air temp • Inflows / weather stations M et Hydrology: • Pan evap Streamflows Station • Produces information on snowpack, • Solar SEAFM • Reservoir Data radiation Levels streamflows and reservoir level, • Wind among other items • Cedar and T olt watersheds calibrated and modeled separately Characterized by land segments o
Hydrologic Segments – Cedar River
Hydrologic M odel Uses • Used in day-to-day operational decisions Dynamic rule curve o Predicting runoff o • Snow (SWE) • Seasonal M id-range probability forecasts o • Inflows / Water operations Hydrology: Streamflows Utility • • Flood Run M odes: SEAFM Planning • Reservoir operating Levels plan Probabilistic forecast – able to o consider El Nino Forecast – short term flood o management Calibration – using data from 1929 o • Can produce inflow weekly inflow datasets to feed into CUE • SPU gains insights about watershed sensitivity to various weather conditions
System M odeling – Probabilistic Seasonal Forecasts Forecast of Chester Morse Lk Elev Initial Conditions on 3/19/2005, Forecast Data thru 3-25 3-1 -05 > 4-14-05 ( 275cfs Sockeye ), 10-8>12-30 (275cfs Low-Normal) Flashboards 1550' & Min. Pool 1520' 1564 Max. Elev.Feb1-1555, Feb 15-1555, Mar 1-1555, Mar 15-1558, Apr 1-1563 1560 1556 1552 Chester Morse Lake Elevation, feet 1548 1544 1540 1536 1532 1528 1524 1520 Actual for Current Year Actual Average for WY 1989-02 1516 Normal - Most Likely to Occur Dry - 1 in 4 Chance Very Dry - 1 in 10 Chance Wet - 1 in 4 Chance 1512 HCP Alert Phase Very Very Dry - 1 in 20 Chance 1532 1508 1504 1500 1/1 1/11 1/21 1/31 2/10 2/20 3/2 3/12 3/22 4/1 4/11 4/21 5/1 5/11 5/21 5/31 6/10 6/20 6/30 7/10 7/20 7/30 8/9 8/19 8/29 9/8 9/18 9/28 10/8 10/18 10/28 11/7 11/17 11/27 12/7 12/17 12/27 Almost 15 billion gallons are stored between elevations 1536 and 1562 feet Pumps would be turned on at elevation 1536 feet and more than 1.5 billion gallons between elevations 1532 and 1536 feet.
Wrap Up and Conclusions Built up capacity over past four years • Answer questions, understand impacts, inform adaptation • Collaborate • Understand strengths and limitations of climate assessment tools • Deploy utilities modeling expertise, tacit knowledge • Opportunities for co-production •
Thank Y ou
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