2025 Orange County Water Demand Projection Model
𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑈𝑠𝑒 𝑝𝑒𝑟 𝐴𝑐𝑐𝑜𝑢𝑛𝑡 = 𝐶 ூ௧௧ + 𝐶 ோ × 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑊𝑎𝑡𝑒𝑟 𝑃𝑟𝑖𝑐𝑒 + 𝐶் × 𝐻𝑖𝑠𝑡𝑜𝑟𝑖𝑐𝑎𝑙 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒𝑠 + ⋯
Equation ES-2
The coefficients explain how (both in terms of magnitude and sign) water use responds to changes to explanatory variables. Hazen identified driver units based on data provided by agencies and the Center for Demographic Research at Cal State Fullerton (CDR) that can be easily projected into the future. The rate of water use per driver is based on agency provided billing sector uses from 2010 through 2024. Table ES-1 shows the driver units and rate of use for each of the four models.
Table ES-1: Summary of Demand Sectors
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
The rates of water use for each sector model are based on the historical responses to explanatory variables, and the future values of those explanatory variables. Addressing multiple influences on demand improves the accuracy and precision of all estimated parameters, and the Hazen team identified a large range of explanatory variables based on our experience with demand modeling and available data. Table ES-2 displays the explanatory variables.
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Appendix G - 11
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