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Yolo Subbasin GSP Implementation

The YSGA received $1.7 million in grant funding from DWR's SGMA Implementation Grant to complete tasks related to implementing the Yolo Subbasin Groundwater Sustainability Plan (GSP). Completion of these tasks will promote groundwater sustainability by investing in data, analyses, and investigations to fill data gaps, educate beneficial users of the current groundwater conditions, and inform better decision-making. More information on each task can be found below:

  1. Develop GSP Annual Reports, GSP Updates based on DWR’s Comments, and a Fee Study for Long-Term Financing of the YSGA includes the development of annual reports for Water Years 2022, 2023, 2024, and 2025, as well as completion of updates to the GSP. This will support the YSGA in preparing the 2027 GSP Update based on comments received from DWR on the 2022 GSP. This task will also include the necessary outreach and communication for refining the GSP, incorporating new technical tasks (discussed below), and successfully implementing the GSP. This task also includes a fee study and public outreach component for the long-term financing of the YSGA to identify an equitable mechanism for providing SGMA compliance across the Yolo Subbasin.
  2. Complete Groundwater Model Enhancements involves updating the model and water budget in the GSP, calibrating and refining model inputs, outputs, and parameterization, and incorporating improved evapotranspiration data. The model will be updated by extending the historical simulation period from 2018 to 2022, incorporating updated land use data, forecasting land use changes and their impact on the water budget, and updating surface water inputs to better reflect the reality of drought conditions. Additionally, the modeled demand of managed wetlands will be revised to better reflect on-the-ground conditions, Capay’s Integrate Groundwater Surface Water Model will be integrated, and additional projects and management actions will be incorporated as they are implemented.
  3. Develop an Approach to Refine Interconnected Surface Water Sustainable Management Criteria includes regional coordination and technical work to further refine the sustainable management criteria for undesirable result 6 (depletion of interconnected surface waters). This task will develop a technical methodology for using groundwater levels as proxies for developing the measurable objectives and minimum thresholds for interconnected surface water thresholds based on DWR’s guidance and experts (consultants) of stream-aquifer interaction.
  4. Conduct GPS Subsidence Survey Updates allows for ground-truthing of DWR’s recent satellite dataset by conducting a new survey of the Yolo Subsidence Network. This involves reconnaissance of existing survey points, creating an observation plan, and adding new survey points in the Capay Valley. Once data has been collected from all the survey points, the data will be analyzed and processed into a final written report. The most recent survey of the subsidence network was conducted in 2016, and the final report can be found here.
  5. Develop a Hungry Hollow Area Projects and Management Actions White Paper includes developing a water budget for the Hungry Hollow watershed and hydrogeologic delineations, developing short-term on-farm pilot project opportunities, outreach to the Hungry Hollow Area beneficial users, and identifying long-term projects and management actions. The Hungry Hollow Area is considered a Yolo Subbasin “Area of Special Concern” due to the recent trend in declining groundwater levels.
  6. Complete Monitoring Network Enhancements to Address Data Gaps includes updating and maintaining the YSGA’s data management system (WRID), mapping the Groundwater Dependent Ecosystems utilizing aerial imagery, and adding monitoring wells in data gap areas (by connecting to existing wells). Updating and maintaining the data management system will be accomplished by converting the WRID to a modern interface for facilitating mobile data collection and allowing for storage of larger datasets, adding support for additional sustainability indicators (such as water quality, subsidence, etc.), adding support for connection to DWR’s Enterprise system, and updating the YSGA’s website to support the WRID improvements.