San Diego County Sustainable Groundwater Management


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Groundwater in San Diego County

San Diego County overlies a complex, finite, yet renewable groundwater resource that varies greatly throughout the region. This resource provides the only supply of water for most residents living in the eastern two thirds of the County (shown in green on map). The western portion of the County is mostly supplied with imported water from member agencies of the San Diego County Water Authority.

Much of the unincorporated area of the County is underlain by fractured rock aquifers, which are present in the foothills and mountainous regions. Due to low storage capacity, replenishment to fractured rock aquifers can cause relatively fast rises to the water table, which conversely can have relatively fast declines to the water table from groundwater pumping in years with low precipitation. Consequently, wells completed in fractured rock are more susceptible to going dry during extended drought conditions.

To facilitate drought and water shortage preparedness for state small water systems and domestic wells, Planning & Development Services in collaboration with the Department of Environmental Health and Quality maintains a list of drought resources (provided below) to implement short- and long-term solutions for residents and communities facing a risk of water shortage.

The Sustainable Groundwater Management Team evaluates projects for potential impacts to groundwater, implements the Sustainable Groundwater Management Act (SGMA) and tracks groundwater conditions throughout County.

Map of groundwater in San Diego County

Groundwater Ordinance and CEQA

To protect, preserve, and maintain groundwater resources in the county, the San Diego County Groundwater Ordinance was enacted in 1991 to ensure that development would not occur in groundwater-dependent areas of the County unless adequate groundwater resources are available to serve both the existing users and the proposed development. In addition to the Groundwater Ordinance, the California Environmental Quality Act (CEQA) requires that certain findings be made in order for a proposed project to be approved. The County CEQA Guidelines for Determining Significance – Groundwater Resources provides guidance for evaluating potential environmental effects that a proposed project may have on groundwater resources in the unincorporated County.

Sustainable Groundwater Management Act (SGMA)

Facing a prolonged statewide drought and unfettered groundwater pumping, California passed the Sustainable Groundwater Management Act (SGMA) in 2014 – providing a framework to regulate groundwater for the first time in California’s history. This historic law sought to strengthen local groundwater management of basins most critical to the state’s water needs.

SGMA requires medium- and high-priority basins identified in Bulletin 118 to be sustainably managed by local public agencies (e.g., counties, cities, and water agencies) who become groundwater sustainability agencies, or GSAs.  The primary purpose of the GSAs is to develop and implement a Groundwater Sustainability Plan (Sustainability Plan) to achieve long-term groundwater sustainability.

Comprehensive stakeholder involvement is critical to sustainable groundwater management, and SGMA requires GSAs to involve stakeholders and interested parties in implementation of SGMA.

SGMA in San Diego County

In San Diego County, the State has designated three of the county’s basins as medium- or high-priority and subject to SGMA: Borrego Valley (Borrego Springs Subbasin), San Luis Rey Valley (Upper San Luis Rey Valley Subbasin), and San Pasqual Valley. 

Map of groundwater subbasins in San Diego County

SGMA Implementation Timeline

SGMA has set the following deadlines in order to prevent state intervention:

Deadline: Action:
June 30, 2017 Formation of Groundwater Sustainability Agencies (GSAs)
January 31, 2020 Adoption of Groundwater Sustainability Plans (Sustainability Plans)
Critically Overdrafted Basins (e.g., Borrego Springs Subbasin)
January 31, 2022 Adoption of Sustainability Plans        
Other Basins (e.g., Upper San Luis Rey Valley, San Pasqual Valley)
20-Year Implementation Period Implementation of Sustainability Plans

Groundwater Monitoring

To track aquifer conditions in groundwater-dependent areas, the Sustainable Groundwater Management Team monitors water levels, maintains general well information and soil data, and compiles precipitation and reservoir evaporation data. Over the years, the County’s water level network of monitored wells has grown to more than 400 wells.

Map of County groundwater monitoring network

Resources and General Information

For More Information

If you have additional questions about San Diego County Sustainable Groundwater Management, please email

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SGMA in San Diego County is funded, in part, by the Water Quality, Supply and Infrastructure Improvement Act of 2014, administered by State of California, Department of Water Resources.