Item 21 - Public Hearing - Resolutions Approving the 2025 Urban Water Management Plan and the 2025 Water Shortage Contingency Plan

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202S WATER SHORTAGE CONTINGENCY PLAN MAY 2026/FINAL DRAFT/CAROLLO Water demands in a five-year consecutive drought are calculated as a 3 percent increase in water demand above a normal year for each year of the drought (MWDOC, 2025). For the City, the five consecutive dry year demand scenario is based on the demand model's multiple dry year methodology. In accordance with the econometric demand model approach used to develop UWMP demand projections, a single hot/dry year was first identified based on weather conditions that produced the greatest demand response. Consecutive dry years were then represented by applying incremental scaling factors to this single hot/dry year demand to account for the compounding effects of persistent warm and dry conditions over time.These scaling factors show long-term relationships between regional water use and multi-year temperature and precipitation deficits and are applied sequentially to simulate second through fifth consecutive dry years. This approach is consistent with the demand modeling framework summarized in Chapter 7 of the City's UWMP. Planned Water Use for Current Year Considering Dry Subsequent Year Water Code Section 10632 (a)(2)(B)(ii) requires the AWSDA to determine "current year available supply, considering hydrological and regulatory conditions in the current year and one dry year."The AWSDA will include two separate estimates of the City's annual water supply and unconstrained demand using: (1) current year conditions; and (2) assumed dry year conditions. The AWSDA will include two separate estimates of City's annual water supply and unconstrained demand using: (1) current year conditions; and (2) assumed dry year conditions.Accordingly, the AWSDA's shortage analysis will present separate sets of findings for the current year and dry year scenarios.The Water Code does not specify the characteristics of a dry year, allowing discretion to the Supplier.The City will use its discretion to refine and update its assumptions for a dry year scenarios in each AWSDA as information becomes available and in accordance with best management practices. Supply and demand analyses for the single-dry year case was based on conditions affecting the SWP as this supply availability fluctuates the most among MET's, and therefore the City's sources of supply. Severe drought conditions in 2021-2022 affected must of the Western United States, including the Colorado River system, which caused its water supply decrease.As conditions worsened, Lake Mead and Lake Powell (the largest storage units in the system), had a combined total storage capacity of 25 percent in 2022, a significant decrease from 39 percent in 2021 (MWDOC, 2025). The Orange County Water Demand Projection Model isolated the impacts that weather and future climate can have on water demand through the use of a statistical model.The impacts of hot/dry weather conditions are reflected as a percentage increase in water demands from the normal year conditions. For a single dry year condition (FY 2013-14), the model projects a 3 percent increase in demand for the OC Basin area where the City's service area is located (MWDOC, 2025). Detailed information about the model is included in the City's 2025 UWMP. The City has documented that it is 100 percent reliable for single dry year demands from 2025 through 2050 with a demand increase of 3 percent from normal demand with significant reserves held by MET, local groundwater supplies, and conservation (Santa Ana, 2026). 3.2.2.6 Infrastructure Considerations The AWSDA will include consideration of any infrastructure issues that may pertain to near-term water supply reliability, including repairs, construction, and environmental mitigation measures that may CITY OF SANTA ANA