Presentation to Scripps Institute of Oceanography City of San Diego Water Demand Forecast Public Utilities Department Engineering Program Management Division Feryal Moshavegh, Associate Engineer Michael Voss, Assistant Engineer May 25, 2010
City of San Diego Population 1.3 million Service Area covers 403 square miles 2
San Diego s Water Treatment Plants
# ## # The Water System Includes: 28 Potable Water Reservoirs 47 Potable Water Pump Stations Miramar Water Treatment Plant 15 505 Miles of Transmission Pipelines 5 805 805 52 67 3,000 Miles of Distribution Pipelines 8 134 Pressure Zones 163 94 125 54 # # # # 5 805 905
Potable Water Model The detailed Water Model analyzes the entire water distribution system: 6,000 major valves 280,000 customer meter connections 667 pressure regulators Interface with GIS, CIS and SCADA systems On going calibration, updates from SCADA every 15 minutes
North City & South Bay Recycled Water System The Recycle Water Model consists of: 2 Reclamation Plants 94 miles of pipelines 404 customer meter connections 6 Pump Stations 5 Reservoirs 8 Pressure zones Interface with GIS, CIS & SCADA
Raw Water Model The Raw Water Model consists of: 40 miles of Pipelines 2 Pump Stations (Lakeside & El Monte) 3 Reservoirs (Murray, El Capitan, and San Vicente) CWA 1st Aqueduct connection Lakeside PS San Vicente Reservoir El Capitan Reservoir Lake Murray
The Year 2030 Master Plan Model Model is based on latest water demand projection report. It includes: Future growth (latest SANDAG release population & land use Water & Sewer Rate Conservation parameters Global Warming effects
How are the models used? Master Planning Operation support, system optimization, shutdown & backup studies New development, cast iron replacement group job studies Pressure zone studies & fire flow analysis Water quality analysis Water source contribution (tracer studies) Emergency planning and water security analysis Quality control check of GIS, CIS and SCADA data
Development of Water Demand Forecasts 10
Demand Forecast Report Objectives Demand Forecasts are used to: Plan for expansion of system capacity (sources of supply, transmission, treatment). Evaluate the effectiveness (or water savings) of alternative conservation measures Prepare contingency plans for water shortages caused by drought or source contamination Guide development (Urban Water Management Plan) 11
Data Used for Water Demand Forecast SANDAG 2050 Update, Series 12 Employment (totals & NAICS) SF and MF occupied households SF and MF housing density (computed from acreage) Median household income Marginal price of water & sewer Weather data historical observed Climate change scenarios Historical Water use data Customer billing information, premise code, and month Wholesale water use Percent NRW from annual report Conservation savings and future programs
Model Weather Variables Weather variables: Average maximum daily temperature Monthly total precipitation Number of rainy days in month One and two month lag effects for precipitation variables (varies by sector) Measured as departure from normal (average) weather
Global Climate Change Data Models provided by Scripps Two global climate models selected: Geophysical Fluid Dynamics Laboratory (GFDLCM2) National Center for Atmospheric Research Parallel Coupled Model (NCARPCM) Data used: Monthly average maximum daily temperature Monthly total precipitation Number of days in each month with precipitation greater than 0.01 inches
Scripps Data Processed Data provided for a 200 x 200 km grid Grids selected that overlay with weather station data used to develop demand forecast model CDM calculated moving average of data to capture trends forecast model estimates demand in 5 year increments and single year climate change data not representative of trend Data then transformed to departure from historical average
Climate Grids for City of San Diego Service Area
Modeled Demand with Climate Change Calculated climate change departures in weather input into forecast model for future years Estimates a per unit use under the given scenario 2030 demands under GFDLCM2 conditions can increase by 4.5% from the average weather scenario
Comparison of Historical Average and Scripps Climate Change Models NCARPCM GFDLCM2 Historical Average 7 6 5 No. Rainy Days 4 3 2 1 0 123456789101112123456789101112123456789101112123456789101112123456789101112 2010 2015 2020 2025 2030 Number of Rainy Days in Month
Comparison of Historical Average and Scripps Climate Change Models NCARPCM GFDLCM2 Historical Average 2.5 2.0 Precipitation 1.5 1.0 0.5 0.0-0.5 1234567891011121 2 3 4 5 6 7 8 9101112123456789101112123456789101112123456789101112 2010 2015 2020 2025 2030 Monthly Precipitation
Comparison of Historical Average and Scripps Climate Change Models NCARPCM GFDLCM2 Historical Average 85 80 75 Temperature 70 65 60 55 50 123456789101112123456789101112123456789101112123456789101112123456789101112 2010 2015 2020 2025 2030 Temperature
Historical Population and Water Demand
Comparison of Demand under Climate Change Scenarios (MGD)
Questions and Comments? Contact Information: Feryal Moshavegh (858) 654 4241 fmoshavegh@sandiego.gov Michael Voss (858) 654 4246 mvoss@sandiego.gov 23