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Outdoor Use Figure 2. Percent of the Theoretical Irrigation Requirement (TIR) applied to landscape. /oi ....... .................................................... 25% 6oi....... .......................................... esoi ....... .......................................... (n=838) w 4W/o 20% v [Low/Deficit v LL a IM .... OnTarget—moi t Excess - Mo....... s 10% Low/Deficit Target Excess 5% OW/oofTlR 70%-13MofTlR >13Mof fft Outdoor water use was studied more extensively in REU2016 than REU1999, specifically, the efficiency of landscape irrigation. The Landscape Group was comprised of a sample of 838 homes selected as a representative subset from participating water utilities. Local weather conditions, irrigated area, water cost and type of plant material are major drivers of outdoor use. The outdoor water use category is comprised of water uses like landscape irrigation, water used through hose bibs, water for filling and backwashing swimming pools, water for washing pavement and cars, and so forth. While the average annual use for all sites (23,749 homes) was 88,000 gphy, the Landscape Group's annual use averaged 101,000 gphy, of which outdoor use constituted 50 percent or 50,500 gphy. To analyze outdoor water use, the estimated actual use was compared to the theoretical irrigation requirement—an equation used for optimal plant growth for agricultural crops. The theoretical irrigation requirement is considered the amount of irrigation that is theoretically required, although many landscapes can thrive on a lesser amount. The theoretical irrigation requirement was customized for each lot in the Landscape Group, considering irrigation area, groundcover type, and other local factors. The majority of study participants -72 percent—applied considerably less water than was theoretically required and were termed "low/deficient irrigators." Sixteen percent of study participants were considered "target" irrigators, because they applied close to the theoretical irrigation requirement. A small group of over -irrigators applied gross excess water compared to the estimated theoretical requirement. This 13 percent accounts for the bulk of excess irrigation for the whole group. Figure 3. Distribution of application ratios, 25% Landscape Group (n=838) 20% v [Low/Deficit v LL 15% OnTarget—moi t Excess - s 10% 5% N% e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e e d 00 00000..N .ormmo..N .ormmo ApplicaDon RaDo 6 1 RESIDENTIAL END USESOF WATER, VERSION 2: EXECUTIVE REPORT