Petaluma Valley groundwater benefitting from innovative collaboration

The recently released 2024 Annual Report finds that Petaluma Valley’s groundwater levels have recovered from the most recent drought throughout most areas of the subbasin, and that continued improvements are possible as innovative new projects come online.

Only three years into its implementation of a landmark 2022 groundwater management plan, the Petaluma Valley Groundwater Sustainability Agency is achieving its sustainability goals, according to a report released on April 1. The 2024 Petaluma Valley Annual Report shows that groundwater levels in both deep and shallow wells have remained steady over time. Additionally, there have been no signs of problems like poor water quality or seawater mixing into the groundwater.

“Like everywhere in California, Petaluma Valley’s groundwater is vulnerable during long droughts and to climate change,” said Sonoma County Supervisor David Rabbitt, who is chairman of the Petaluma Valley Groundwater Sustainability Agency. “The groundwater agency’s close collaboration with the city of Petaluma is a big step toward efficiently and cost-effectively climate-proofing our groundwater.”

One project is especially focused on basin resiliency to future droughts. The city of Petaluma recently constructed 1.2 miles of recycled water pipeline along Maria Drive on the east side of the city. State grant funding from the groundwater agency allowed the pipeline to be extended from Lucchesi Park to South McDowell Boulevard. The pipeline installation was paired with the complete reconstruction of the existing two-lane road, including the addition of new curb ramps, signalized crosswalks and traffic-calming measures.

“This project and the partnership with the groundwater sustainability agency, was a win-win-win,” said Petaluma Mayor Kevin McDonnell. “Residents benefitted from major road improvements. By leveraging the groundwater agency’s funding, Petaluma was able to extend the pipeline, which will ultimately lead to more than 13 million gallons per year of potable water savings for the city and its customers while protecting local groundwater supply.”

The recycled water pipeline was completed in November 2024. The city’s upcoming rebate program will offer financial assistance to help connect qualified customers with dedicated irrigation meters located along the recycled water pipeline so they can use recycled water for irrigating farms and landscapes.

The 2022 groundwater sustainability plan noted that information about groundwater levels and quality was scarce in some areas of the basin. Collaboration between the groundwater agency and the city, supported by grant funding from the California Department of Water Resources, is helping fill these gaps with the construction of four new multilevel groundwater monitoring wells that will provide valuable insight into what is happening underground.

One well, located in Oak Hill Park, was originally planned to provide back-up water supply for the city but initial drilling for the well revealed that the potential water production from the location would be too low. The city then collaborated and shared costs with the groundwater agency to repurpose the project and convert the already completed borehole into a new monitoring well. Data from the new monitoring well will provide valuable groundwater level readings in an area of the basin with sparse data.

A second planned monitoring well, located in Del Oro Park in east Petaluma has a dual purpose. In addition to providing long-term water level data for the groundwater agency, the well will also measure the effect of a planned pilot project to recharge the aquifer through a nearby injection well. The injection well is part of an innovative aquifer storage and recovery pilot project, in which clean drinking water would be pumped underground when the supply is plentiful to be stored for use in emergencies and future droughts. This project is leveraging separate state grants received both by the city and the groundwater agency.

Additional monitoring wells are also planned to help improve the understanding of groundwater levels and the potential for seawater intrusion and that will help evaluate the relationship between groundwater pumping and surface water depletion.

Both the monitoring wells and the injection well were funded by grants from the state of California. State grant funding is also paying for three programs available to Petaluma Valley’s groundwater users, which can be found (along with other information) at https://petalumavalleygroundwater.org/. For more information about the City of Petaluma’s water resources, go to https://cityofpetaluma.org/water-service/.