2025 Urban Water Management Plan

Section 7 2025 Urban Water Management Plan Water Supply Reliability Assessment City of Pleasanton Public Draft | May 2026 7-15 EKI Environment & Water, Inc. 7.5 Drought Risk Assessment In addition to the long-term water service reliability assessment presented above, the DRA evaluates Pleasanton’s supply risks under a severe drought period lasting for the next five consecutive years after the assessment is completed (i.e., 2026-2030). The DRA is intended to inform the DMMs and water supply projects and programs to be included in the UWMP (Section 9). Suppliers may conduct an interim update or updates to this DRA within the five-year cycle of its UWMP update (i.e., before the 2030 UWMP). 7.5.1 Data, Methods, and Basis for Water Shortage Condition Similar to the reliability analysis described in Section 7.2, Pleasanton’s DRA is based on Zone 7’s DRA due to Pleasanton’s reliance on water purchases from Zone 7. As presented in Section 7 of Zone 7’s 2025 UWMP, the DRA assumes 30%, 10%, 41%, 6%, and 6% Table A allocations for 2026-2030, respectively. Data for 2026 reflects projected water year supply availability based on currently available data. Data for 2027-2030 reflect the last four years of the multiple-dry year scenario previously discussed (1988-1991). Zone 7’s supply projections are based on existing facilities and the expected availability of supplies from various sources given the constraints previously described. A five-year modeling analysis using 2025 conditions as the initial baseline was conducted. This approach accounts for differences in demand levels and the availability and timing of supply sources during the 2026-2030 planning period. 7.5.2 Drought Risk Assessment Individual Water Source Reliability Table 7-7 summarizes Zone 7’s available supplies for each year of the DRA. In addition to potable water supplies from Zone 7, the City is expected to produce 3,500 AFY of groundwater in each year of the drought. For the DRA, recycled water supplies are assumed to be sufficient to meet recycled water demands.  CWC §10635(b) Every urban water supplier shall include, as part of its urban water management plan, a drought risk assessment for its water service to its customers as part of information considered in developing the demand management measures and water supply projects and programs to be included in the urban water management plan. The urban water supplier may conduct an interim update or updates to this drought risk assessment within the five- year cycle of its urban water management plan update. The drought risk assessment shall include each of the following: (1) A description of the data, methodology, and basis for one or more supply shortage conditions that are necessary to conduct a drought risk assessment for a drought period that lasts five consecutive water years, starting from the year following when the assessment is conducted. (2) A determination of the reliability of each source of supply under a variety of water shortage conditions. This may include a determination that a particular source of water supply is fully reliable under most, if not all, conditions. (3) A comparison of the total water supply sources available to the water supplier with the total projected water use for the drought period. (4) Considerations of the historical drought hydrology, plausible changes on projected supplies and demands under climate change conditions, anticipated regulatory changes, and other locally applicable criteria.