Stanislaus County is underlain by four groundwater subbasins of the San Joaquin Valley Groundwater Basin. In most of Stanislaus County, groundwater has historically been managed sustainably through conjunctive use with surface water. However, the four groundwater subbasins began experiencing storage depletion and other stresses resulting from various sources, including:
- Drought conditions
- New groundwater demand to supply the conversion of rangeland to agricultural production in the eastern portion of the county
- Increased reliance on groundwater in the western portion of the county in areas where surface water deliveries have become unreliable
To address the above stresses and promote compliance with the Sustainable Groundwater Management Act (SGMA), Stanislaus County was the first county in California to adopt a Groundwater Ordinance for a discretionary well-permitting program. Trihydro supported Stanislaus County in implementing its discretionary well-permitting program by developing the procedure used to review groundwater permit applications to ensure potential impacts to water systems were evaluated prior to approvals.
To demonstrate sustainability, Trihydro based the groundwater permit application review procedure on applicable California Environmental Quality Act (CEQA) thresholds, management objectives, trigger levels, and response actions for each potential “undesirable result” defined in SGMA and the Groundwater Ordinance. Undesirable results include:
- Chronic local and regional drawdown of groundwater levels
- Depletion of groundwater storage
- Groundwater quality degradation
- Land subsidence
- Surface water depletion
- Additionally, two of the subbasins have been designated as critically overdrafted by the Department of Water Resources (DWR) due to overdraft conditions outside the county.
For each undesirable result, permit application requirements, action thresholds, and standard permit conditions were specified. Trihydro also developed a program guide, permitting and CEQA evaluation flow chart, checklists for exemptions and application completeness, and a technical review form that promotes a consistent and defensible approach for each application review.
Trihydro also assisted Stanislaus County in obtaining a Proposition 1 grant from DWR to prepare a Program Environmental Impact Report (PEIR) that evaluated the potential environmental impacts associated with Groundwater Ordinance implementation. The PEIR was adopted in 2018 and included the creation of a county-wide surface and groundwater model to assess potential impacts related to drawdown, groundwater storage depletion, subsidence, surface water depletion, and impacts to groundwater-dependent ecosystems.
Since the implementation of the discretionary well-permitting program, Trihydro has continued to support Stanislaus County by reviewing groundwater permit applications to evaluate potential impacts to groundwater and surface water bodies and confirm compliance with Groundwater Ordinance sustainability requirements.
Outcomes:
- Streamlined and defensible well-permitting program compliant with the Groundwater Ordinance, CEQA, and SGMA
- Regional surface and groundwater model
- Completion of a CEQA Program Environmental Impact Report for the County’s Discretionary Well Permit Program
- Procurement and administration of a $500k Proposition 1 Groundwater Sustainability Planning Grant
- Development and implementation of sustainable water management strategies