TO: 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: Comment letter on the State Water Resources Control Board’s Water Supply and Demand Assessment for the Napa River Watershed
RECOMMENDATION
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Authorize submittal of a comment letter authored by the NCGSA’s Groundwater Technical Advisory Group (TAG) to the State Water Board expressing concerns related to the State Water Resources Control Board’s Supply and Demand Assessment Unit and Paradigm Environmental, Inc.’s project to model surface water supply and demand in the Napa River Watershed. (No Fiscal Impact)
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BACKGROUND
The State Water Resources Control Board (State Water Board) first introduced NCGSA staff to a project of their Supply and Demand Assessment Unit (SDA) at a virtual meeting on November 14, 2023. State Water Board staff described a new initiative wherein the Napa River Watershed was selected as a Pilot Watershed for a modeling project with the State Water Board and their consultants, Paradigm Environmental, Inc., entitled “Modeling Water Supply and Demand in the Napa River Watershed”. The State Water Board is responsible for allocating surface water through California’s water rights priority system. The presentation provided an overview of the modeling effort proposed in the Napa River Watershed, which is to develop a water supply (hydrologic) model that assesses surface water availability where low flows and drought conditions may threaten water supplies, impair critical habitat, and/or create uncertainty for water users. The State Water Board’s stated objective is to better allocate surface water through California’s water rights priority system during critical drought periods to maintain water supplies in the Napa River critical for habitat and species. The model simplifies the important interactions between groundwater and surface water in the Napa River Watershed.
On February 20, 2024, State Water Board staff, NCGSA staff and technical consultants met to discuss the Napa Valley Integrated Hydrologic Model (NVIHM) developed as an integral part of the Napa Valley Subbasin Groundwater Sustainability Plan (GSP) and NCGSA staff strongly recommended the NVIHM be integrated into the State Water Board’s modeling effort. NCGSA staff had previously provided detailed background information about the NVIHM and a presentation with additional information about future model-related efforts, including ongoing refinement of surface water and groundwater interaction and the effects of drought and pumping on variability in surface water flows. The State Water Board held three public meetings on May 14, May 21, and June 3, 2024 about similar modeling efforts in other watersheds. Members of the NCGSA technical team attended the June 3rd meeting and the NCGSA staff and technical team subsequently expressed concerns to the State Water Board related to the way groundwater interactions within the selected watersheds were represented in the State Board’s model.
On September 12, 2024, the State Water Board and Paradigm Environmental, Inc., were invited to make a presentation to the TAG on their project. The TAG posed questions and expressed several concerns regarding the proposed modeling to the State Water Board and its consultants. Namely, the TAG expressed concern about the State Water Board’s model:
(1) Presents an overly simplified approach to groundwater and surface water interactions in Napa Valley, which have been well studied and incorporated into local efforts to model groundwater;
(2) The impact of surface water curtailments could lead to further groundwater pumping by irrigators in lieu of surface water diversions; and
(3) Concerns about the lack of integration of the State Water Board’s model with the existing NVIHM, which was created and is actively used to model groundwater and surface water in the Napa River Watershed by the NCGSA.
The TAG remains concerned that utilizing a separate surface water model that does not accurately use and incorporate existing groundwater data and knowledge about surface water and groundwater interactions will lead to conflicting results and discrepancies. These discrepancies could lead to difficulties in communicating differences between model results to stakeholders within the Napa Valley and could undermine efforts by the NCGSA to work with stakeholders on implementing five workplans which have been prepared and adopted by the GSA. The workplans include:
• Napa County Water Conservation Workplan
• Groundwater Pumping Reduction Workplan
• Interconnected Surface Water and Groundwater Dependent Ecosystems (GDEs) Workplan
• Stormwater Resource Plan
• Communication and Engagement Plan
On October 23, 2024, NCGSA staff made a formal Public Records Act request for two draft technical reports related to SDA and Paradigm Environmental’ s surface water modeling efforts in two other watersheds, South Fork Eel River and Shasta River. Staff expected to receive a response to the PRA request by November 14, 2024. State Water Board notified County staff that additional time was necessary to complete review and disclosure of these records and anticipate disclosing the records no later than Friday, November 22, 2024. A letter from the State Water Board on November 22 indicated that the requested 2021 and 2022 documents are still under review, and the documents are being withheld under two exemptions to disclosure.
On November 6, State Water Board staff reached out to NCGSA staff to coordinate a meeting to discuss the State Water Board’s decision to couple a MODFLOW type model with the State Water Board’s surface water model for the Napa River.
On November 14, 2024, at the regular monthly TAG meeting, TAG members discussed submission of a draft letter prepared by two TAG members that, upon concurrence from other TAG members on November 14, would be finalized and submitted to the Board Members of the State Water Board. The TAG hopes that a letter to the leadership of the State Water Board will prompt SDA and Paradigm Environmental, Inc. to carefully consider integrating the NVIHM into their model to ensure that any modeled surface water results from this effort do not harm the work of the NCGSA.
On November 14, the TAG voted to approve a comment letter and is herein requesting the NCGSA approve the TAG to formally submit a letter expressing their concerns to the State Water Board regarding this effort and to encouraging closer collaboration with the NCGSA.
On November 21, the SDA and its modeling team met with NCGSA staff and its technical consultants to discuss the State Water Board’s decision to couple a groundwater flow model to the preliminary surface water model in order to achieve an integrated groundwater and surface water flow model. The State Water Board expressed its interest in receiving the NVIHM files and will prepare a Workplan Addendum to reflect the development of an integrated hydrologic model. The State Water Board also expressed its intent to collaborate with the NCGSA on 1) the preparation of the Workplan Addendum, and 2) public outreach to inform stakeholders of the State Water Board’s modeling efforts and coordination with the County. NCGSA staff appreciate the State Water Board’s plans to update its approach to modeling the Napa River Watershed and to collaborate with the County on stakeholder outreach efforts. Because of the importance of interconnected surface water and groundwater in the Napa River Watershed, NCGSA staff recommend that a Memorandum of Understanding be developed to formalize these mutually agreeable intentions.
Although encouraging steps by the SDA have occurred since the November 14 TAG meeting, the TAG requests the NCGSA approve the TAG to formally submit a letter expressing their concerns to the State Water Board to ensure the SDA pursues appropriate modeling of interconnected surface water and groundwater and closer collaboration occurs with the NCGSA.
Requested Action:
Authorize NCGSA staff to submit letter of concern to the SWRCB Board Members on behalf of the Napa County Groundwater Technical Advisory Group.
FISCAL & STRATEGIC PLAN IMPACT
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Is there a Fiscal Impact? |
No |
ENVIRONMENTAL IMPACT
ENVIRONMENTAL DETERMINATION: The proposed action is not a project as defined by 14 California Code of Regulations 15378 (State CEQA Guidelines) and therefore CEQA is not applicable.