Vina Subbasin boards expand groundwater early-warning network to 25 wells
Vina GSA, California · Meeting date: November 4, 2026 · Published: November 5, 2026
The Vina and Rock Creek GSA boards have directed staff to extend Local Management Levels across all 25 representative monitoring wells outside Chico and to prescribe monitoring, notification and investigation steps when a trigger is reached. The move strengthens the proposed Groundwater Sustainability Plan's early-warning framework, although the agencies remain divided over how far below measurable objectives those levels should sit.
Key points
- The boards directed staff to assign Local Management Levels to all 25 representative monitoring wells in the North and South management areas, up from 14 wells in the public-review drafts.
- A trigger will be a confirmed static fall groundwater measurement below the Local Management Level in two consecutive calendar years.
- Once triggered, the framework will include monthly monitoring and outreach or notification to domestic well owners within the affected monitoring polygon.
- The Chico Urban Forest Vulnerability Assessment will be elevated to a GSP project, while two shallow Chico wells will be added to the representative monitoring network.
- An ad hoc group will address the unresolved choice between Local Management Levels set 15 feet or 20 feet below measurable objectives, as well as whether to retain the GSP's non-dry-year provision.
Full report
Vina Groundwater Sustainability Agency and Rock Creek Reclamation District GSA have agreed to extend groundwater early-warning levels to all 25 representative monitoring site wells in the Vina Subbasin's North and South management areas, replacing the more limited 14-well approach in the public-review draft of the amended Groundwater Sustainability Plan.
The direction is a substantive expansion of the proposed Local Management Level system, a non-regulatory tool intended to identify declining groundwater conditions before minimum thresholds are reached. The boards also agreed on a more specific trigger: a Local Management Level will be activated when a confirmed static fall measurement is below the level in two consecutive calendar years.
Once that threshold is met, the amended plan will require monthly monitoring and outreach or notification to domestic well owners in the relevant monitoring polygon. Staff will revise the plan's Local Management Level language using Rock Creek's proposed step-by-step framework, alongside the Stakeholder Advisory Committee's recommendations on added monitoring and notification.
The response framework presented to the boards includes confirmation that the measurement reflects static conditions, investigation of potential causes and effects, assessment of impacts across sustainability indicators, and reporting to the agencies' advisory committee and boards. Rock Creek's proposed framework calls for a technical committee to report its findings and recommendations within 180 days of triggering measurements, after which the boards would consider potential actions through a public process.
The boards also confirmed the addition of two shallow groundwater wells, CMW-102A and SWMW-06A, to the Chico Management Area monitoring network. The additions bring the full representative monitoring site network to 31 wells. Minimum thresholds for the two new wells are set at 30 feet below ground surface.
Separately, the boards agreed to move the Chico Urban Forest Vulnerability Assessment from an "Other Projects" category into the GSP's formal project list. The assessment is intended to address a stated gap in understanding of whether deep-rooted valley oaks in Chico's urban forest depend on shallow groundwater and are vulnerable to changes in that system. The project will no longer be tied to a Local Management Level trigger, as no such levels are being assigned in the Chico Management Area.
The two agencies did not resolve the central calibration question for the expanded early-warning system. The Stakeholder Advisory Committee recommended setting Local Management Levels 15 feet below each measurable objective, while Rock Creek supports a 20-foot offset. Rock Creek said a 15-foot setting could initiate investigations at groundwater levels observed at some wells during years when the subbasin was healthy. Staff said that none of the wells would have met the proposed two-consecutive-fall-measurement trigger under the 15-foot approach.
The boards also deferred a decision on retaining the plan's non-dry-year language in the definition of undesirable results. Vina's board had previously directed its removal, while Rock Creek supports keeping the provision and the public-review drafts retain it. An ad hoc group of board representatives, supported by staff and counsel, will seek language on both unresolved issues before the joint boards' December 9 public hearing on the periodic evaluation and amended GSP.
This summary was generated by AI based on the source document and may contain errors.
Source: Board Meeting, Vina GSA