TO: Technical Advisory Group for the Napa County Groundwater Sustainability Agency
FROM: Brian D. Bordona, Director of Planning, Building and Environmental Services
REPORT BY: Jamison Crosby, Natural Resources Conservation Manager
SUBJECT: Update on the Napa Valley Subbasin Periodic Evaluation
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RECOMMENDATION
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Provide an update on the Napa Valley Subbasin Groundwater Sustainability Periodic Evaluation required to be submitted by the Napa County Groundwater Sustainability Agency to the California Department of Water Resources by January 31, 2027. The update includes information on various water conservation and groundwater pumping reduction projects and management actions underway.
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Procedure
Staff introduces.
Questions and answers with the TAG.
Public comments.
BACKGROUND AND DISCUSSION
In September 2026, the NCGSA technical team provided the TAG with a preliminary overview of the development of the Napa Valley Subbasin Periodic Evaluation (PE). The PE is required to be submitted by the Napa County Groundwater Sustainability Agency (NCGSA) to the California Department of Water Resources (DWR) by January 31, 2027. The November TAG meeting will provide:
A refresher on the Periodic Evaluation requirements,
A summary of groundwater conditions over a 10-year period (Spring 2016-Spring 2025) and annual and cumulative change in groundwater storage through Spring 2026,
A summary of the results for the six sustainability indicators,
Updates since the September TAG meeting to sustainable management criteria for the reduction in groundwater storage and interconnected surface water sustainability indicators, and
Updates pertaining to various water conservation and groundwater pumping reduction projects and management actions.
The PE is an evaluation and written assessment of an approved Groundwater Sustainability Plan (GSP) to occur at least every five years and when a Plan is amended (the Periodic Evaluation is due no later than five years after initial GSP ...
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