Title
Update on Monterey County Water Resources Agency engagement in groundwater management activities
a. Groundwater Monitoring Program
b. Salinas River Discharge Measurement Series
c. Planning and Technical Support for the Salinas Valley Basin Groundwater Sustainability Agency
d. Groundwater Monitoring and Remedial Measures Plan for the Monterey Peninsula Water Supply Project
Report
SUMMARY/DISCUSSION:
a. Groundwater Monitoring Program
In October 2024, the Board of Supervisors of the Monterey County Water Resources Agency (“Agency”) adopted Ordinance No. 5426 and approved the Agency’s Groundwater Monitoring Program (“GMP”) Manual. Since that time, the Agency has implemented the well registration, groundwater elevation monitoring, groundwater quality monitoring for seawater intrusion, and groundwater extraction monitoring components of the GMP. Some components of the GMP occur year-round, such as monthly groundwater level monitoring, while others like water quality monitoring for seawater intrusion are seasonal and occur primarily during the summer months.
In May 2026, Agency staff began the annual water quality sampling of wells in the Deep Aquifers, as described in the “Monitoring Plan for the Deep Aquifers,” which was prepared by the Agency and adopted by the Board of Supervisors of the Agency in December 2025. The results from Deep Aquifers water quality sampling are used to identify changes in water chemistry, discern any indications of seawater intrusion, and provide data to inform the depositional environment and age of groundwater in the Deep Aquifers. As of the date of this report, laboratory analysis of the 2026 Deep Aquifers water quality samples is ongoing.
In June 2026, Agency staff began collecting groundwater samples as part of the program that monitors water quality for seawater intrusion. Production wells in the 180/400-Foot Aquifer, Eastside Aquifer, and Monterey Subbasins are sampled twice per year, in June and August, and monitoring wells are sampled once in September. The resulting data from these events are used by the Agency to develop maps of the extent of seawater intrusion in the Salinas Valley Groundwater Basin and quantify changes and variability in groundwater chemistry within and ahead of the mapped seawater intrusion extent, and by external Groundwater Sustainability Agencies to evaluate subbasin-specific Sustainable Management Criteria in the Langley Subbasin and three aforementioned Subbasins. Laboratory analysis of samples collected in June and August is ongoing. The remaining sample collection will occur beginning on September 15, 2026.
On August 23, 2026, Agency staff completed the annual August Trough groundwater level measurement event. This component of the groundwater level monitoring program involves collecting measurements at approximately 140 wells on a single Sunday to capture a snapshot of groundwater conditions within and ahead of the area with mapped seawater intrusion at a time of the year with peak groundwater pumping. Data generated by the August Trough event will be used to develop groundwater elevation contour maps, assess regional groundwater conditions that contribute to seawater intrusion, and evaluate annual changes in groundwater levels and storage.
b. Salinas River Discharge Measurement Series
During the last week of August 2026, Agency and U.S. Geological Survey (“USGS”) staff completed the Salinas River Discharge Measurement Series (“River Series”), an annual streamflow measurement survey of the Salinas River that provides information essential to understanding the hydrologic conditions that affect water management along the Salinas River.
Prior to and during the River Series, reservoir releases are held constant and discharge (i.e., streamflow) measurements are performed at multiple locations along the Salinas River during a discrete period of time. The resultant streamflow measurements are analyzed to inform the Agency’s understanding of groundwater-surface water interactions along the length of the Salinas River below Nacimiento and San Antonio dams. Data collected during the 2026 River Series are being analyzed and a report with the results will be forthcoming in late 2026.
c. Planning and Technical Support for the Salinas Valley Basin Groundwater Sustainability Agency
The Salinas Valley Basin Groundwater Sustainability Agency (“SVBGSA”) is preparing amendments to the Groundwater Sustainability Plans (“GSPs”) for the six subbasins where it has management responsibilities. During July and August 2026, Agency staff provided planning and technical support to the SVBGSA by reviewing drafts of the GSP amendments and providing input on topics such as the GMP, Agency facilities and operations, and future projects and management actions.
d. Groundwater Monitoring and Remedial Measures Plan for the Monterey Peninsula Water Supply Project
In April 2012, California American Water Company (“CAWC”) filed an application with the California Public Utilities Commission (“CPUC”) for approval of the Monterey Peninsula Water Supply Project (“MPWSP”). As proposed, the MPWSP would include slant source water wells, a desalination plan, product water pipelines, and related appurtenant facilities.
In December 2012, the Agency and CAWC entered into a Settlement Agreement and Mutual Release, adopted by the CPUC in March 2015, wherein, among other things, CAWC agreed to promptly pay the costs of the Agency’s implementation of a groundwater monitoring plan throughout the life of the MPWSP or its successor. Subsequent actions related to the Agency’s role in monitoring for the MPWSP include (1) CPUC certification of an environmental impact report and adoption of Applicant Proposed Measure 4.4-3, wherein CAWC agreed to work with the Agency to develop a monitoring and reporting program to provide early warning of any potential negative effects to groundwater levels or groundwater salinity as a result of the MPWSP (September 2018); and (2) California Coastal Commission (“CCC”) approval of coastal development permits for the MPWSP that include Special Condition 12, requiring preparation of a Groundwater Monitoring and Remedial Measures Plan (“GMRMP”) to be reviewed and approved by the CCC (November 2022).
In September 2025, Agency staff engaged with CAWC to review and comment on an initial draft of the GMRMP. Since that time, Agency staff has continued to work with CAWC on subsequent drafts of the GMRMP and preparation of a Master Agreement for Professional Services (“Master Agreement”) to define the scope and terms of the Agency’s implementation of the GMRMP. Currently, the Master Agreement is under review by the Agency and CAWC, and the GMRMP is under review by the CCC.
The Agency’s required level of effort and staffing needs are expected to increase once the GMRMP is approved and a Master Agreement is executed, both of which are precursors to beginning implementation of the data collection, analysis, and reporting described in the GMRMP. The implementation phase could begin as soon as early 2027 but the timeline remains uncertain.
OTHER AGENCY INVOLVEMENT:
Staff from the USGS participated in the Salinas River Discharge Measurement Series. CAWC is involved with the GMRMP. County Counsel is participating in review of the Master Agreement with CAWC.
FINANCING:
Funding for the GMP is provided through the GMP Fees, which is included in the Fiscal Year (“FY”) 2026-27 Adopted Budget in Fund 1501. The total estimated amount of the GMP for FY 2026-27 is $802,536 and appropriations in the FY 2026-27 Adopted Budget are sufficient for this program.
Funding for Agency staff time to complete data collection and analysis for the River Series is provided from Fund 1501 and appropriations in the FY 2026-27 Adopted Budget are sufficient for this program. Funding for USGS staff support of the River Series is provided through a Joint Funding Agreement, the Agency’s portion of which is included in Fund 1503 of the FY 2026-27 Adopted Budget.
Funding for Agency staff time to provide planning and technical support services to the SVBGSA, up to $125,000 for FY 2026-27, is provided through a Memorandum of Understanding between the Agency and SVBGSA. The full amount of the MOU is included in the FY 2026-27 Adopted Budget in Fund 1501.
Funding for the GMRMP will be provided by CAWC but is not included in the FY 2026-27 Adopted Budget (Fund 1501) because the scope of services and terms have not yet been finalized.
Prepared by: Amy Woodrow, Senior Water Resources Hydrologist, (831) 755-4860
Approved by: Ara Azhderian, General Manager, (831) 755-4860