2025 Orange County Water Demand Projection Model
4.2.7
Persons Per Household
The ACS-derived single-family and multifamily PPH estimates were calibrated to align with the CDR’s single-family and multifamily projected housing unit data.
4.2.8
Relative Sectoral Employment
Ratios of sectoral employment were included as explanatory variables in the CII model sector. These sectoral employment ratios represent the estimated mix of CII activity within each retail service area. The projected number of jobs by sector was obtained from the 2025 CDR projections of four aggregated NAICS sectors.
4.2.9
Seasonality
Seasonal indices were included as explanatory variables in the water demand model. These seasonal indices are represented in the model as a sine/cosine pair of variables to capture the cyclical monthly pattern in water use, where demands are generally higher in the summer and lower in the winter. Most sectors had a single sine/cosine pair representing the seasonal cycle; some have two sine/cosine pairs to more effectively capture seasonal effects associated with the academic calendar. These factors are maintained for the forecast horizon.
4.2.10
Conservation
The 2021 Orange County Residential Water Efficiency Potential and Opportunities Study (2021 Study) assumes that total County-wide passive conservation in the residential sectors will increase by 695 acre- feet per year through 2030, after which it will remain constant. The conservation increase to 2030 represents a 1.9% decrease in annual demand, as shown in Table 4-4 .
Table 4-4: Projected County-wide Passive Conservation 4
Passive Conservation Volume (AFY)
Percent Demand Reduction
Year
Residential Demand (AFY)
2025
222,572
695
0.31%
2026
222,572
1390
0.62%
2027
222,572
2085
0.94%
2028
222,572
2780
1.25%
2029
222,572
3475
1.56%
2030
222,572
4170
1.87%
2035
1.87%
2021 Study does not report post-2030 demand and conservation; percent demand reduction is assumed to stay constant
2040-2050
1.87%
4 Data shown on Table 4-4 were obtained from the 2021 Orange County Residential Water Efficiency Potential and Opportunities Study.
4-8
Appendix G - 61
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