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2025 URBAN WATER MANAGEMENT PLAN <br /> MAY 2026/FINAL DRAFT/CAROLLO <br /> Table 4.8 Future Model Parameters <br /> Data Category Variable Source Assumptions <br /> Driver Units Single-Family and CDR Historical households per account; averages are <br /> Multi-Family Accounts multiplied by households projected by CDR <br /> Irrigation Accounts Agency Billing Data Accounts are assumed to be constant into the future <br /> Sectoral Employment CDR Proportion of jobs within CII sectors projected by <br /> CDR <br /> Explanatory V Monthly Maximum PRISM 30-year historical normal weather <br /> Variables Temperature and Total <br /> Precipitation <br /> [Water Price Retail Agencies Prices increase by 3%per year above inflation for <br /> 2025-2030 and keeps pace with inflation thereafter <br /> (zero difference from inflation trend) <br /> Water Use Restrictions State and Local None <br /> Restrictions <br /> Seasonality Sine/cosine functions to capture monthly pattern <br /> Median Income U.S. Census Constant income at 2022 value(real dollars) <br /> Housing Density i CDR Derived from CDR housing unit projections, <br /> assuming residential area remains at 2024 levels <br /> Persons Per Household CDR CDR-projected demographics <br /> Gross Domestic Federal Reserve Long-term GDP trend <br /> Product <br /> Relative Sectoral CDR Calculated based on CDR projections <br /> Employment <br /> Passive Efficiency Flume Insight Assumes a 2%decrease in residential demand due <br /> Estimates to conservation by 2030(linearly extrapolated),then <br /> no change <br /> COVID Binary Indicator None(occurred between March 2020 and <br /> May 2023) <br /> The normal year scenario was provided by the baseline forecast. In this model, the single dry year scenario <br /> used a hot-dry index (HDI) to identify the year with the most weather-sensitive demand,with 2014 <br /> selected for most agencies. The multiple dry year was developed to describe the potential impact of <br /> consecutive dry years. <br /> The forecasts for individual agencies, including the City's, was then summed to the regional level, <br /> providing regionally consistent forecasts for all of Orange County. <br /> 4.4 Water Loss <br /> The City has conducted annual water loss audits since 2015 per the AWWA methodology per SB 555 to <br /> understand the relationship between water loss, operating costs, and revenue losses. Non-revenue water <br /> for FY 2020-2024 consists of three components: real losses (e.g., leakage in mains and service lines, and <br /> storage tank overflows), apparent losses (unauthorized consumption, customer metering inaccuracies, and <br /> systematic data handling errors), and unbilled water(e.g., hydrant flushing, firefighting, and blow-off <br /> water from well start-ups).Table 4.9 summarizes the status of the last five years of water loss audit <br /> CITY OF SANTA ANA <br />