2025 Orange County Water Demand Projection Model
𝑄 = 𝑁 ⋅ 𝑞 → 𝑞 = ொ ே
Equation 2-6
To be useful for model development and forecasting, driver units must have a consistent historical record coincident with consumption and have a corresponding future dataset representing projected driver unit counts. Driver units were selected for each model sector, as shown in Table 2-3 . The following sections detail the data sources and data processing used to develop estimates of drivers for each retail agency and model sector.
Table 2-3: Driver Units and Rates of Use for each Demand Sector
Sector
Driver Units
Rate of Use Definition
Single-family Residential
Gallons / account / day
Accounts
Multifamily Residential
Gallons / account / day
Commercial, Institutional, Industrial (CII)
Jobs
Gallons / job / day
Dedicated Irrigation (potable, recycled & raw water)
Accounts
Gallons / account / day
Other water uses that are small and do not neatly fit above classifications are projected using a long-term average of historical consumption.
2.1.4
Residential Housing Units
Driver units for both single-family and multifamily residential water use were set to the number of accounts provided by retail agencies. Distinct housing unit data was available through the Center for Demographic Research at California State University, Fullerton (CDR) by retailer service area boundaries. The number of single-family accounts recorded by retail agencies may be slightly greater than the number of single-family housing units reported by CDR due to auxiliary dwelling units (ADUs), other property- specific meter additions, and subtle differences in how the single-family class is defined (e.g., some agencies may include individually metered townhomes). Multifamily dwellings are generally billed collectively on a single meter, and the number of units per account is higher than for single-family accounts. The total number of accounts are used as a driver for the residential sectors, and units per account is used as an explanatory variable providing a means of using CDR projections of residential households as a driver for residential sector forecasts. Both values are reported in Table 2-4 .
2-6
Appendix G - 25
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