Item 28 - Urban Water Management Plan and Water Shortage Contingency Plan

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Santa Ana 2020 Urban Water Management Plan arcadis.com 7-13 and some non-irrigation applications. OCWD’s GWRS and GAP allow Southern California to decrease its dependency on imported water and create a local and reliable source of water that meet or exceed all federal and state drinking level standards. Expansion of the GWRS is currently underway to increase the plant’s production to 130 MGD, and further reduce reliance on imported water. Implementation of demand management measures during dry periods: During dry periods, water reduction methods to be applied to the public through the retail agencies, will in turn reduce the City’s overall demands on MET and reliance on imported water. The City’s specific demand management measures are further discussed in Section 9. Drought Risk Assessment Water Code Section 10635(b) requires every urban water supplier include, as part of its UWMP, a DRA for its water service as part of information considered in developing its DMMs and water supply projects and programs. The DRA is a specific planning action that assumes the City is experiencing a drought over the next five years and addresses the City’s reliability in the context of presumed drought conditions. Together, the water service reliability assessment (Sections 7.1 through 7.3), DRA, and WSCP (Section 8 and Appendix H) allow the City to have a comprehensive picture of its short-term and long-term water service reliability and to identify the tools to address any perceived or actual shortage conditions. Water Code Section 10612 requires the DRA to be based on the driest five-year historic sequence of the City’s water supply. However, Water Code Section 10635 also requires that the analysis consider plausible changes on projected supplies and demands due to climate change, anticipated regulatory changes, and other locally applicable criteria. The following sections describe the City’s methodology and results of its DRA. 7.5.1 DRA Methodology The water demand forecasting model developed for the Demand Forecast TM (described in Section 4.3 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 condition are reflected as a percentage increase in water demands from the average condition (average of FY 2017-18 and FY 2018-19). For a single dry year condition (FY 2013-14), the model projects a 6% increase in demand for the region encompassing the City’s service area (CDM Smith, 2021). Locally, the five-consecutive years of FY 2011-12 through FY 2015-16 represent the driest five consecutive year historic sequence for the City’s water supply. This period that spanned water years 2012 through 2016 included the driest four-year statewide precipitation on record (2012-2015) and the smallest Sierra Cascades snowpack on record (2015, with 5% of average). It was marked by extraordinary heat: 2014, 2015 and 2016 were California’s first, second and third warmest year in terms of statewide average temperatures. Locally, Orange County rainfall for the five year period totaled 36 inches, the driest on record.