Basin Prioritization

Map of draft 2018 SGMA Basin Prioritization. Contact DWR to receive more information about this map.
Statewide Map of SGMA 2019 Basin Prioritization

California’s 515 groundwater basins are classified into one of four categories; high-, medium-, low-, or very low-priority based on components identified in the California Water Code Section 10933(b).

Basin priority determines which provisions of California Statewide Groundwater Elevation Monitoring (CASGEM) and the Sustainable Groundwater Management Act (SGMA) apply in a basin. During the prioritization process, the best available datasets and information are applied in a consistent, statewide manner in accordance with the provisions in the California Water Code.

DWR was first directed to prioritize basins as part of the Groundwater Monitoring legislation enacted in California's 2009 Comprehensive Water Package. DWR prioritized groundwater basins through the CASGEM Program and released the results in 2014.

In 2015, SGMA went into effect and required DWR to prioritize basins when basin boundaries are modified. In 2015, DWR used the 2014 CASGEM Basin Prioritization as the initial SGMA basin prioritization.

In 2016, DWR received 54 requests for basin boundary modifications. DWR released the final groundwater basin boundaries, which incorporated numerous statewide jurisdictional and scientific modifications. In December 22, 2016, DWR published Bulletin 118 Interim Update 2016, which included the boundary modifications and required DWR to reassess basin prioritization. 

In January 2019, DWR released SGMA 2019 Basin Prioritization Phase 1 for 458 of the 515 basins that were not affected by 2018 Basin Boundary Modifications. The results from the basin boundary modifications were released in February 2019. The 57 basins which were affected by these modifications were prioritized in SGMA 2019 Basin Prioritization Phase 2. Draft results from Phase 2 have been released and are expected to be finalized in early summer 2019.


In January 2014, we conducted five  workshopsto introduce draft 2014 Basin Prioritization results and solicit public comments. Final 2014 Basin Prioritization results are compiled into a summary table available in PDF or Excel format.

CASGEM BP 2014 Final Table
CASGEM Basin Prioritization 2014 Final Results | (Publish Date:
Detailed spreadsheet of 2014 Final Basin Prioritization Results which includes values used in determining the individual component ranking values, organized by basin number.

The Water Code requires a statewide prioritization, to the extent that data are available, of California's groundwater basins using the following eight components (Water Code §10933):


  1. Population
  2. Rate of population growth
  3. Number of public supply wells
  4. Total number of wells
  5. Total irrigated acreage
  6. Degree to which persons overlying the basin rely on groundwater as their primary source of water
  7. Documented impacts on the groundwater within the basin, including overdraft, subsidence, saline intrusion, and other water quality degradation
  8. Any other information determined to be relevant by the department, including adverse impacts on local habitat and local streamflows

A priority designation of high, medium, low, or very low is assigned to each groundwater basin. For details on how changes in priority affect local agency compliance with SGMA, refer to establishment of Groundwater Sustainability Agencies (GSAs).