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2025 URBAN WATER MANAGEMENT PLAN <br /> MAY 2026/FINAL DRAFT/CAROLLO <br /> CHAPTER 7WATER SERVICE RELIABILITY AND DROUGHT <br /> RISK ASSESSMENT <br /> This chapter of the Urban Water Management Plan (UWMP) describes the City of Santa Ana's water <br /> service reliability assessment for three long-term hydrological conditions: a normal year, a single dry year, <br /> and a drought period lasting five consecutive years.The Drought Risk Assessment (DRA) assesses water <br /> supply reliability during a severe drought lasting the next five consecutive years, from 2026 to 2030. <br /> Factors affecting reliability, such water quality, regulations and climate change, are also summarized in <br /> this assessment of reliability. <br /> 7.1 Water Service Reliability Overview <br /> As part of the UWMP, every urban water supplier is required to assess the reliability of their water service <br /> to its customers under a normal year, a single dry year, and multiple dry years. Santa Ana's water sources <br /> are from local groundwater, recycled water, and imported water purchased from the Metropolitan Water <br /> District of Southern California (MET), which imports water from the Colorado River through its own <br /> Colorado River Aqueduct (CRA) and from Northern California through the California Aqueduct managed <br /> by the State Water Project (SWP). Santa Ana is one of 26 member agencies of MET. <br /> MET has also invested in numerous programs and projects to augment its direct deliveries of imported <br /> water such as water transfers, groundwater banking, and use of its reservoir storage as summarized in <br /> Chapter 6. <br /> Local groundwater in the Orange County Groundwater Basin (OC Basin) is managed by the Orange <br /> County Water District (OCWD). As summarized in Chapter 6, OCWD has developed programs and projects <br /> to improve groundwater recharge and augment groundwater through recycled water, conjunctive use, <br /> and water transfers. OCWD assesses groundwater conditions and sets its Basin Production Percentage <br /> (BPP), the percentage of each Producer's total water supply that comes from groundwater pumped from <br /> the OC Basin, and the Basin Equity Assessment (BEA),which is a surcharge for exceeding the BPP. <br /> Currently, the BPP is set at 85 percent. Likewise, MET has also invested in numerous programs and <br /> projects to augment its direct deliveries of imported water such as water transfers, groundwater banking, <br /> and use of its reservoir storage as summarized in Chapter 6. MET's draft 2025 UWMP demonstrates that <br /> MET will be able to meet its projected water demands for the next 25 years under normal, dry, and <br /> multiple dry year conditions (MET, 2025). <br /> In 2025, all water agencies in Orange County, in collaboration with their wholesalers, the Municipal Water <br /> District of Orange County (MWDOC) and OCWD, developed a water demand forecast model for their <br /> service areas that estimated water demand at the individual retail water agency level.The demand model <br /> statistically correlates municipal and industrial (M&I)water use with demographic, socioeconomic, <br /> conservation, and weather variables as reported in the 2025 Orange County Water Demand Projection <br /> Model TM (MWDOC, 2025). Because the model isolates weather, future water demand can be estimated <br /> under single and multiple-year droughts and under future climate change scenarios.The model used a <br /> 33-year dataset (1991-2024) to estimate demand under average (normal), single-dry year, and five <br /> consecutive dry years hydrologic conditions. Correlation coefficients between demand, temperature, and <br /> CITY OF SANTA ANA <br />