Water Utility M odeling at Seattle Public Utilities Paul Fleming M - - PowerPoint PPT Presentation

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
• Part of Executive Branch
• Budget/ rates approved by City Council
• Federal statutory requirements
• 1.4 million retail and wholesale customers
• ~ 1400 employees
• Water M anagement responsible for modeling, system operations
• Long Term Planning responsible for planning
• Climate and Sustainability responsible for climate issue

• Responsibilities:
• Water supply for people
• Instream flows for salmon

habitat in perpetuity

• Flood management
• Hyrdopower generation
• 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 System

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

100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000 900,000 1,000,000 1,100,000 1,200,000 1,300,000 1,400,000 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 20 40 60 80 100 120 140 160 180 200 220 240 260 280

Non-Revenue Billed Consumption Total Consumption Population

Since the peak in 1984, total consumption has fallen 27% while population has grown by 25%.

Adaptation and M itigation

• Adaptation
• Identifying impacts
• Pursuing “ no regrets” options
• Enhancing our knowledge
• Building internal capacity
• Collaborating
• M itigation
• Finalizing GHG inventory
• Assessing potential for climate neutrality

Engagement and Collaboration

Challenges and Issues

• Projecting climate impacts on supply
• Effects on snowpack – timing and quantity
• Changes in precipitation
• Return of fall rains
• Projecting climate impacts on quality
• Extreme events
• Frequency and extent of forest fires
• 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
• USDA/ NRCS SnoT

el sites

• NOAA/ NWS daily and mid range weather forecasts
• NOAA’s Climate Prediction Center 30-90 day outlooks
• NOAA/ NASA remote sensing of snowpack
• Applications
• Inform short term operational needs and longer term planning

horizons

• Compliance with instream flows
• Inform reservoir management and releases
• Project water supply availability

Chain of M odels

Utility Planning

Hydrology

S ystem M odel

GCM Down- scaling

Utility M odeling

• Historic

Inflows

• Gaged Flows
• Calculated
• Reconstructed

from correlations

Hydrology

• Firm Yield
• Simulation

Results

System M odel: CUE

• New Source

Decisions

• Capital

Programs

• Negotiations

Water Utility Planning

• Precip
• Air temp
• Pan evap
• Solar

radiation

• Wind

M et Station Data

• Snow (SWE)
• Inflows /

Streamflows

• Reservoir

Levels Hydrology: SEAFM

• Seasonal
• perating plan

(refill, instream flows, etc.)

• Flood
• perating

Water Utility Planning

Conjunctive Use Evaluation (CUE) M odel

• Simulates reservoir and river
• perations at weekly timestep
• M odels entire system - Cedar,

SF T

• lt, Lake Y
• ungs (optional)
• Programmed in Stella to

enable users to set

• perating rules
• Uses historic inflow data
• Reconstructed 81 years,

starting in 1929

• Can also use other inputs
• Provides SPU with insights

about system performance and vulnerabilities

• Firm Yield
• Simulation

Results

• Historic

Inflows

• Gaged Flows
• Calculated
• Reconstructed

from correlations

Hydrology System M odel: CUE

Water System M odel Uses

• Estimating firm yield
• Optimizing use of multiple sources,

maximizing of existing

• Determining yield from new supply

alternatives, impacts on reservoir levels and streamflows

• Impacts of long term flood

management operations

• Evaluating instream flow regime

proposals

• Establishing management triggers
• Determining frequency of critical
• perations
• Assessing climate impacts to all of

the above

• Firm Yield
• Simulation

Results

System M odel: CUE

• New Source

Decisions

• Capital

Programs

• Negotiations

Water Utility Planning

Seattle’s Hydrology M odel - SEAFM

• Continuous watershed simulation

model with hourly timestep

• Based on HSPF
• Also using HFAM
• Driven by met data from nearby

weather stations

• Produces information on snowpack,

streamflows and reservoir level, among other items

• Cedar and T
• lt watersheds calibrated

and modeled separately

• Characterized by land segments
• Precip
• Air temp
• Pan evap
• Solar

radiation

• Wind

M et Station Data

• Snow (SWE)
• Inflows /

Streamflows

• Reservoir

Levels Hydrology: SEAFM

Hydrologic Segments – Cedar River

Hydrologic M odel Uses

• Used in day-to-day operational

decisions

• Dynamic rule curve
• Predicting runoff
• M id-range probability forecasts
• Run M odes:
• Probabilistic forecast – able to

consider El Nino

• Forecast – short term flood

management

• Calibration – using data from 1929
• Can produce inflow weekly inflow

datasets to feed into CUE

• SPU gains insights about watershed

sensitivity to various weather conditions

• Snow (SWE)
• Inflows /

Streamflows

• Reservoir

Levels Hydrology: SEAFM

• Seasonal
• perations
• Flood
• perating

plan Water Utility Planning

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' 1500 1504 1508 1512 1516 1520 1524 1528 1532 1536 1540 1544 1548 1552 1556 1560 1564

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

Chester Morse Lake Elevation, feet

Actual for Current Year Actual Average for WY 1989-02 Normal - Most Likely to Occur Dry - 1 in 4 Chance Very Dry - 1 in 10 Chance Wet - 1 in 4 Chance HCP Alert Phase Very Very Dry - 1 in 20 Chance 1532

Almost 15 billion gallons are stored between elevations 1536 and 1562 feet and more than 1.5 billion gallons between elevations 1532 and 1536 feet. Pumps would be turned on at elevation 1536 feet

• Max. Elev.Feb1-1555, Feb 15-1555, Mar 1-1555, Mar 15-1558, Apr 1-1563

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

• u