2025 Orange County Water Demand Projection Model
4. Future Demand Analysis The four sector-specific econometric models are used to establish baseline demand projections from 2025 to 2050 at a monthly timestep for each retail agency 1 . Prior to forecasting, the models are calibrated to a specific observation year, and other uses are quantified (other uses are miscellaneous uses not included in the original four demand sectors). Hazen worked with each agency separately to change the calibration factors or household and job variables to yield a forecast start year value (Fiscal Year 2024-2025) that was reasonably close to agency observations. Calibration refers to adjustments for residual biases in the output of fitted econometric models to establish a historical point in time to anchor projections of the future to a recent, representative historical period for each agency and sector. The calibration approach implemented a simple scalar calibration at the per‑account (rate‑of‑use) level for each agency and sector. The use of simple scalar (i.e., a constant multiplicative factor) preserves the econometric relationships (e.g., weather and price elasticities) while removing differences/errors in the statistical model predictions for the selected calibration period. For each member agency and model sector a calibration factor was calculated as the ratio needed to make the model’s average predicted per‑unit use equal the observed per‑unit use over the selected calibration period. Calculated factors were then applied multiplicatively to all forward-looking monthly rate‑of‑use predictions. Model output for each sector (water use per unit) was multiplied by calibration factors to account for biases in the historical model fits. Calibration factors were derived from the ratio of predicted to observed water demand for historical normal weather years for each retail agency, or historical water demand based on agency-requested time periods ( Equation 4-1 ).
ு௦௧ (௦௩ௗ) ௪௧ ௨௦ ௌௗ (ௗ௧ௗ) ௪௧ ௨௦
𝐶𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 𝐹𝑎𝑐𝑡𝑜𝑟 =
Equation 4-1
Calibration factors were unique to each retail agency and sector and are summarized in Table 4-1 .
Table 4-1: Calibration Factors
SF Calibration Factor
MF Calibration Factor
CII Calibration Factor
Irr Calibration Factor
Agency
Anaheim
0.99 1.00 0.99 1.06 1.00 1.03 1.01 1.02
0.99* 1.00 0.99 0.99 1.00 1.01 1.00 1.01
1.09* 0.98 1.04 0.99 1.02 1.04 0.98
0.78 1.08 0.97 0.99 0.69 0.33 0.99 0.99
Brea
Buena Park
East Orange CWD
El Toro WD
Fountain Valley
Fullerton
Garden Grove
1.32
1 Due to the timing of the project, water use data were collected up to December 2024. The model projections begin in January 2025.
4-1
Appendix G - 54
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