Petaluma Valley



Located in California’s San Francisco Bay hydrologic region, the Petaluma Valley is 46,661.32 acres in size. This Medium priority basin is home to an estimated 54,719 people (2010 value), which have been at a rate of .

Petaluma Valley is a(n) basin with approximately 1145 wells, of which approximately 31 are water supply wells. Groundwater accounts for approximately 27 percent of the basin’s water supply.

Source: CA DWR

Basin Notes

Petaluma Valley Historical Hydrology and Ecology Study

1982: Bulletin 118-4 Evaluation of Ground Water Resources Sonoma County Volume 3: Petaluma Valley

2003: Bulletin 118 basin description

2014: Basin Prioritization note:
Widespread and serious nitrate contamination affecting shallow wells in the upland area NW of Petaluma. Generally poor quality GW south of Petaluma. Potential for seawater intrusion in tidal reaches. Increasing MTBE contamination.(B-118 unpublished data).

2017: Hydrology chapter, Davidon/Scott Ranch GPA, Rezoning, and 1222.001 VTM Revised Draft EIR, Impact Sciences, Inc.

2018: Draft Basin Priority moved from medium to high. Petaluma Valley Groundwater Sustainability response

2018: Basin Prioritization note: 1) CASGEM/WDL/GWIDS: Stable hydrographs. Source: DWR 2) 1) Sources of chloride in the north San Francisco Bay area aquifers include seawater intrusion, thermal water, and dissolved minerals from marine and volcanic rocks. The valleys most affected by large chloride concentrations are the Petaluma, the Sonoma, and the Napa, in which seawater intrusion caused by excessive ground-water withdrawals has been the primary source (fig. 110). Reduced withdrawals and increased surface-water imports have helped alleviate the salinity problem. Source: USGS HA730-B

Basin boundary modification request with Wilson Grove Formation Highlands 1-059 pending

2019: Basin boundary modification approved. Per DWR: It “would revise a portion of the existing shared boundary between the Petaluma Valley basin and the Wilson Grove Formation Highlands basin. The revision would shift a portion of the shared boundary so the vast majority of the City of Petaluma is within the Petaluma Valley basin.” Phase 2 Draft basin priority: medium.


GSA Information