Piloting Utility Modeling Applications: The San Francisco Public Utilities Commission

Transcription

1 Piloting Utility Modeling Applications: The San Francisco Public Utilities Commission David Behar Climate Program Director Alexis Dufour, P.E. Hydrology and Water Systems Modeling PUMA Workshop December 1, 2010 San Francisco

2 The San Francisco Public Utilities Commission 1. Department of City and County of San Francisco million customers wholesale customers in four counties, 800,000 retail customers in City of San Francisco employees 5. Three Enterprises: Water, Wastewater, Power 6. FY budget: $867 million

3 SFPUC assessment work to date 1. Statistical modeling, simple delta method, temperature only, to Developing hydrological modeling tools (Dufour) 3. Treasure Island development Assisting in framing adaptation/adaptive management approach for SLR 4. Co-founder and Chair, Water Utility Climate Alliance

4 Audiences for this work 1. Utility Staff 2. Senior Managers 3. Commission 4. Board of Supervisors 5. Mayor 6. RATEPAYERS (wholesale and retail)

5 Our goals 1. Learn 2. Stay abreast of the science 3. Develop ongoing expert relationships 4. Understand and synthesize uncertainty 5. Advance impacts analysis step-by-step 6. Be the most informed constituency in San Francisco 7. Plan adaptation

6 SFPUC Water System 85% 5% 10%

7 Water Supply Vulnerability to Changing Climatic Conditions: Modeling Approach Climate Modeling & Downscaling Tools Hydrologic models for Sierra Nevada & Bay Area Watersheds Planning Model (HH/LSM) Policy Planning Decision Making (Decision Support Planning Methods) Infrastructure Planning

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9 Assess sensitivity of SPUC water entitlement to changing climatic conditions 20,000 Unimpaired flow at LG Districts Max Rights City entitlement Unimpaired Flow at La Grange TID/MID Entitlements (cfs) 15,000 10,000 5, Water Available to the City (1,000 AF) 0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Water Year 2010 Aug Sep 0

10 Hetch Hetchy Reservoir Snowline in 2000

11 Monthly Hetch Hetchy Inflow Exceedences WY 1931 to 2005 Monthly Inflow (TAF) % 25% 50% 75% 95% Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

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16 Water Supply Vulnerability to Changing Climatic Conditions: Modeling Approach Climate Modeling & Downscaling Tools Hydrologic models for Sierra Nevada & Bay Area Watersheds Planning Model (HH/LSM) Policy Planning Decision Making (Decision Support Planning Methods) Infrastructure Planning

17 Water supply planning model: the Hetch Hetchy and Local System Model HH/LSM mass balance model representation of each operational objective and constraint Excel VBA platform monthly time step recurrence of historical hydrology ( )

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19 Water Supply Vulnerability to Changing Climatic Conditions: Modeling Approach Climate Modeling & Downscaling Tools Hydrologic models for Sierra Nevada & Bay Area Watersheds Planning Model (HH/LSM) Policy Planning Decision Making (Decision Support Planning Methods) Infrastructure Planning

20 HFAM Hydrologic Modeling Tool physically-based conceptual hydrologic model to simulate: snow accumulation and melt, soil moisture and runoff model time step: hourly input: temperature, precipitation, solar radiation, wind movement, and potential evapotranspiration output: snow pack, soil moisture, actual evapotranspiration, streamflow

21 Land Segments defined by: topography (elevation, aspect, slope), mean precipitation, soils/rock, vegetation Size: 2 6 km 2 (500 1,500 acres)

22 HFAM Natural Flow Reaches Legend Rafferty Tuolumne 3020 reach Dana reservoir Delaney reservoir represented as a reach Cathedral gaged reach direction of flow River reaches receive land segment runoff and transport water to reservoirs Matterhorn Register Piute Cr Benson Lake Rancheria Falls Creek Hetch Hetchy Lake Eleanor Cherry Creek Cherry Lake Diversion to Mountain Tunnel South Fork, Tuolumne Clavey River Pine Mountain Lake Big Creek North Fork, Tuolumne Turnback 3290 Moccasin 3295 Sullivan Don Pedro Woods Creek LaGrange

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24 Weather Stations currently used in HFAM 11 stations Period of interest /8 deg( ~12x12km)

25 Water Supply Vulnerability to Changing Climatic Conditions: Modeling Approach Climate Modeling & Downscaling Tools Hydrologic models for Sierra Nevada & Bay Area Watersheds Planning Model (HH/LSM) Policy Planning Decision Making (Decision Support Planning Methods) Infrastructure Planning

26 How to use climate data and climate projections? 1) Methodological approach 2) Hydrologic modeling implementation

27 Methodological approach questions 1. What can we expect from climate models given the uncertainties (forcing, initial conditions, model imperfections)? -> How to use the projections? 2. Should we use ensemble data from the model with the greatest skill or use multi-model ensemble data? 3. Dynamical vs statistical downscaling? 4. Top-down vs Bottom-up

28 Hydrologic modeling questions 1. Temporal distribution of temperature projections on a seasonal and diurnal time scale 2. Sensitivity of temperature projections to elevation 3. Trends for precipitation projections 4. Projections for other variables: Solar radiation, wind, relative humidity

29 Trend in Daily Minimum Temperature at Hetch Hetchy ( )

30 QUESTIONS

31 Current approach to climate change projections A 2A 2B 2C 3A 3B Precipitation Change (% of MAP) Temperature Change (deg C)

32 Data: SFPUC, USGS, NRCS Snotel, NWS Climate Prediction Center, NWS River Forecast Center, IRI Seasonal Forecast Other products from academic institutions Up Country WSFM Base Ops MOS Bay Area Hydrologic Frequency Analysis Qualitative Demand Forecasting Local Reservoir System Model Time scale: Monthly to Seasonal Decisions: releases, pipeline rates, treatment plant rates, instream flow, maintenance outages, transfers

33 Water Supply Forecast Model