GSP Periodic Evaluation
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 page 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.
The table below summarizes significant new information collected since the GSP was adopted, along with links to supporting documents and resources.
Table 1. Summary of New Information Since 2022 GSP Adoption
| Significant New Information (e.g., new monitoring data, reports, coordination with other agencies, data provided by the Department) | Description | Relevant GSP Sections |
|---|---|---|
| Joint GSP Evaluation – North Sacramento River Corridor TM (Montgomery and Associates 2025) | Technical review of adopted and revised GSPs for the North Sacramento River Corridor Subbasins comparing basin setting, water budgets, Sustainable Management Criteria, monitoring networks, and corrective actions to support inter-basin coordination and the 2027 Periodic Evaluation. | Coordination / Adjacent Basins |
| Inter-basin Flow Evaluation with Regional Model TM (Montgomery and Associates 2026) | Regional groundwater modeling analysis using DWR’s C2VSimFG v1.5 to estimate cross-boundary groundwater flows and stream–aquifer interactions, providing long-term and recent average inter-basin flow estimates to support quantitative assessment of boundary conditions for the 2027 Periodic Evaluation. | Basin Setting Coordination / Adjacent Basins |
| Groundwater Monitoring Network Enhancements TM (Larry Walker Associates 2024) | Comprehensive evaluation of the groundwater level monitoring network to identify spatial and vertical data gaps and recommend installation of new shallow wells, a multi-completion well, stream gages, and domestic well monitoring to strengthen aquifer representation, address data gaps, and support the 2027 Periodic Evaluation. | Monitoring Network |
| Butte County Evaluation of Groundwater Level Monitoring Network (Butte County Water and Resource Conservation Department 2025) | Technical evaluation of groundwater level monitoring wells to assess data reliability, spatial distribution, and suitability for Representative Monitoring Site (RMS) designation, supporting potential refinement of the RMS network as part of the 2027 Periodic Evaluation. | Monitoring Network |
| 2025 Groundwater Quality Trend Monitoring Program Results TM (Butte County Water and Resource Conservation Department 2025) | Summary of 2025 salinity monitoring results for RMS wells in the Butte, Vina and Wyandotte Creek Subbasins. Results were evaluated relative to Mos and MTs, and network modification recommendations were documented. No Undesirable Results for groundwater quality were identified. | Monitoring Network Sustainable Management Criteria |
| Butte Basin Groundwater Model (BBGM) Updates TM (Montgomery and Associates 2026) | Technical evaluation and update of the BBGM, including boundary condition refinements, stream-aquifer interaction analysis, regional model comparisons, incorporation of new data, and extension through WY 2024 to support SGMA implementation and the 2027 Periodic Evaluation. | Basin Setting |
| AEM-Based Evaluation of Vina Monitoring Wells (Sub-Terra Heritage Resource Investigations 2024) | Evaluation of Vina monitoring wells using AEM data and borehole logs to identify which aquifer zones are monitored by existing well screens, supporting vertical network representation and future well design. | Basin Setting Monitoring Network |