Item 27 - Water Supply Assessment for Cabrillo Town Center Project

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Santa Ana 2020 Urban Water Management Plan arcadis.com 6-17 6.3.3 Sustainable Groundwater Management Act In 2014, the State of California adopted the Sustainable Groundwater Management Act (SGMA) to help manage its groundwater sustainably, and limit adverse effects such as significant groundwater-level declines, land subsidence, and water quality degradation. SGMA requires all high- and medium-priority basins, as designated by DWR, be sustainably managed. DWR designated the non-adjudicated Coastal Plain of OC Basin (“Basin 8-1” or “Basin”) as a medium-priority basin, primarily due to heavy reliance on the Basin’s groundwater as a source of water supply. Compliance with SGMA can be achieved in one of two ways: 1) A Groundwater Sustainability Agency (GSA) is formed, and a Groundwater Sustainability Plan (GSP) is adopted, or 2) Special Act Districts created by statute, such as OCWD, and other agencies may prepare and submit an Alternative to a GSP (City of La Habra et al., 2017) The agencies within Basin 8-1, led by OCWD collaborated to submit an Alternative to a GSP in 2017, titled the “Basin 8-1 Alternative” to meet SGMA compliance. This document will be updated every five years. The current (2017) version is included in Appendix G. 6.3.4 Basin Production Percentage Background The OC Basin is not adjudicated and as such, pumping from the OC Basin is managed through a process that uses financial incentives to encourage groundwater producers to pump a sustainable amount of water. The framework for the financial incentives is based on establishing the BPP, the percentage of each Producer’s total water supply that comes from groundwater pumped from the OC Basin. Groundwater production at or below the BPP is assessed the Replenishment Assessment (RA). While there is no legal limit as to how much an agency pumps from the OC Basin, there is a financial disincentive to pump above the BPP. The BPP is set uniformly for all Producers by OCWD on an annual basis. Agencies that pump above the BPP are charged the RA plus the Basin Equity Assessment (BEA). The BEA is presently calculated so that the cost of groundwater production is equivalent to the cost of importing potable water supplies. This approach serves to discourage, but not eliminate, production above the BPP, and the BEA can be increased to discourage production above the BPP if necessary. The BPP is set based on groundwater conditions, availability of imported water supplies, and Basin management objectives. The supplies available for recharge must be estimated for a given year. The supplies of recharge water that are estimated are: 1) Santa Ana River stormflow, 2) Natural incidental recharge, 3) Santa Ana River baseflow, 4) GWRS supplies, and 5) other supplies such as imported water and recycled water purchased for the Alamitos Barrier. The BPP is a major factor in determining the cost of groundwater production from the OC Basin for that year. The BPP set for Water Year 2021-22 is 77%. BPP Adjustments for Basin Management OCWD has established management guidelines that are used to establish future BPPs, as seen in Table 6-5. Raising or lowering the BPP allows OCWD to manage the amount of pumping from the basin. OCWD has a policy to manage the groundwater basin within a sustainable range to avoid adverse impacts to the basin. OCWD seeks to maintain some available storage space in the basin to maximize surface water