2025 Orange County Water Demand Projection Model
7. Urban Water Use Objectives (UWUO) Metrics The Urban Water Use Objective (UWUO) requires residential indoor consumption to decrease from 47 GPCD in 2025 to 42 GPCD in 2030 and remain at 42 GPCD through 2050. Although future active conservation is not included in the baseline forecast, the UWUO target residential demand is calculated for each agency in this section, and active conservation may be assumed from these target values and subtracted from the baseline forecast. While the indoor conservation target specified by the UWUO is fixed, the outdoor target depends on precipitation, evapotranspiration, landscape area, and a landscape efficiency factor ( Equation 7-1 ).
௬ ቁ = (𝐸𝑇𝑜 −𝑃𝑒𝑓𝑓)×𝐿𝑎𝑛𝑑𝑐𝑎𝑝𝑒 𝐴𝑟𝑒𝑎 ×𝐿𝐸𝐹 ×0.62
𝑂𝑢𝑡𝑑𝑜𝑜𝑟 𝐵𝑢𝑑𝑔𝑒𝑡 ቀ
Equation 7-1
ETo is local reference evapotranspiration, Peff is effective rainfall, and 0.62 represents a conversion factor from inches to square feet. The landscape efficiency factor (LEF) provides a way to reduce irrigation targets; water use increases as the LEF increases. The California State Water Board requires a LEF of 80% through September 2030, at which point the required LEF decreases to 63%. In October 2035, the LEF decreases to 55% for residential irrigation and 45% for CII irrigation. When/If an agency can comply with the State UWUO outdoor conservation targets is a retail agency determination based on each agency’s unique circumstances. Although the forecasts provided by Hazen do not include active conservation, each retail agency may compare the forecasted gallons per capita per day (GPCD) with their UWUO target to build or forecast an active conservation program.
7-1
Appendix G - 75
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