Under the Sustainable Groundwater Management Act (SGMA), Groundwater Sustainability Agencies must evaluate their Groundwater Sustainability Plans (GSPs) every five years to assess progress toward achieving groundwater sustainability. The Vina Subbasin’s first GSP Periodic Evaluation will be submitted to the California Department of Water Resources (DWR) in January 2027.

This webpage provides information related to the Periodic Evaluation, including new data, studies, and projects completed since the adoption of the GSP. These updates help the GSA assess whether the current plan remains effective or whether adjustments to the basin description, sustainability criteria, or management approach may be needed.  This [Annotated Outline] document is based on DWR guidance and includes the required sections of the Periodic Evaluation, with notes specific to the Vina Subbasin.

Focus of the First Evaluation

The focus of this first Periodic Evaluation is to address the Department of Water Resources’ six Recommended Corrective Actions (from the 2023 Determination Letter) and provide a written assessment of GSP implementation. 

The evaluation will review: 

• Current groundwater conditions and progress toward sustainability goals.
• The status and effectiveness of ongoing projects and management actions.
• Updates to the basin setting based on new data and changes in water use.
• The condition and coverage of our groundwater monitoring networks.

Recommended Corrective Actions (RCA)

RCAs serve as a checklist to strengthen local groundwater management. They typically require the GSA to gather more data, clarify goals, or update management approaches to ensure the subbasin remains on track for long-term sustainability. Addressing these items is a key requirement of the five-year review.

Vina GSA is focused on the following RCAs:

• Add information on groundwater quality conditions and define sustainable management criteria in the GSP.
• Provide consistent information on stream loss and gains throughout the GSP.
• Clarify the criteria used to measure the impacts of lowering the minimum groundwater level thresholds.
• Revise the definition of undesirable results.
• Provide additional information on the criteria used to identify undesirable results and sustainable management criteria for land subsidence.
• Use DWR's interconnected surface water guidance, fill data gaps, prioritize collaboration, and clarify the groundwater level monitoring sites used for evaluation.

Once submitted, DWR will complete its Periodic Review of the Vina GSP and issue a determination of the Plan's status: Approved, Incomplete, or Inadequate.

Supporting Documents

For those interested in more detail, additional supporting materials are available:

Periodic Evaluation Supporting Documents

Share Your Input

Public comment is welcome throughout the Periodic Evaluation process. If you have questions or feedback about the Vina Subbasin's GSP Periodic Evaluation, use the comment form to submit your input.

Strawman Proposals – For Consideration and Discussion

The following strawman proposals (i.e., a preliminary, rough draft intended to spark discussion and gather feedback) are provided to facilitate discussion and solicit public input on specific topics identified in the RCAs and Determination Letter.  Any input received will be incorporated into and inform materials prepared for consideration by the Stakeholder Advisory Committee (SHAC) and then brought forward to the GSA Boards for decision-making.

ISW Memo and Strawman_Final 5.18.2026.pdfLand Subsidence_Memo and Strawman Proposal_4.24.2026.pdf