Upper San Luis Rey Groundwater Sustainability Plan

Customer Profile

The Pauma Valley Groundwater Sustainability Agency (PVGSA) includes:
• Yuima Municipal Water District
• Pauma Municipal Water District
• Pauma Valley Community Services District
• San Luis Rey Municipal Water District
• Upper San Luis Rey Resource Conservation District

Challenge

The Sustainable Groundwater Management Act (SGMA) requires groundwater basins designated as medium or high priority to form a Groundwater Sustainability Agency (GSA). The GSA is responsible for developing and implementing a Groundwater Sustainability Plan (GSP) that considers the interests of all beneficial uses and users of groundwater in the basin. The SGMA also requires that these basins reach and maintain sustainability within 20 years following plan implementation.

The Upper San Luis Rey Valley (USLRV) groundwater basin was designated as a medium-priority basin, which meant it was required to develop a GSP, which includes documenting:
• Plan area and basin setting: a physical description of the basin including historical groundwater budgets and water quality
• Sustainable management criteria: establishing sustainability goals including minimum thresholds, measurable objectives, and measurable interim milestones
• Project and management actions: guidelines to achieve sustainability goals agreed upon by the GSA
• Groundwater sustainability plan implementation: targets for costs, schedule, reporting, and evaluating the implementation

The USLRV groundwater basin, consisting of Pala and Pauma Valleys, includes multiple jurisdictions and land ownership. Reservation land from several tribes including Pala, Pauma, Rincon, and La Jolla are inter-mixed with private property and agricultural land. Because of the small area, consistent pumping, multiple stakeholders with overlapping interests, and past water rights lawsuits, public outreach and communication was an important aspect of the GSP effort. In addition, contract delays due to concerns over stakeholder equity in the basin produced challenging project deadlines and an accelerated timeline for GSP development.

Geoscience Solution

The PVGSA engaged Geoscience to deliver the GSP. Geoscience was a good fit for the project because of previous experience in the project area, a firm focus on sustainable groundwater management, extensive experience with determination of safe yield, and a deep understanding of SGMA.

Geoscience assembled a qualified team and worked with the PVGSA to develop a GSP in accordance with the California Code of Regulations that complied with SGMA and Department of Water Resources (DWR) requirements.

The implementation management plan included performing an aquifer study, analyzing requirements to satisfy the terms of SGMA, and analyzing and assisting with the drilling of a monitoring well to expand the monitoring network in the basin.

While groundwater models are not mandatory under SGMA, they are often recommended by DWR for their ability to provide spatial and seasonal projections of groundwater conditions. Geoscience developed an integrated surface water and groundwater model for the unconsolidated sediments of Pauma and Pala Subbasins. The model was calibrated to observed surface water flow and groundwater elevations for the period from 1991 through 2020. 

In addition to providing a comprehensive and defensible analysis of evaluation criteria required for the GSP chapters (such as water budgets, sustainable yield, effect of climate change, and sustainability goals), the USLR Groundwater Model provides the PVGSA with a valuable management tool that can be used to evaluate proposed basin projects and future management actions. 

Customer Results

Working with limited data, a tight project schedule, and a relatively small budget, Geoscience developed a GSP for review by DWR. The solution included assisting with stakeholder outreach, responding to public comments, and preparing submittal documents, freeing the PVGSA to focus on their core mandates. The project is currently awaiting results of the DWR review.