Groundwater recharge pilot study underway in Sonoma Valley

Posted on March 26, 2018


Test well located at the Sonoma Veterans Memorial Building

Preparation for a groundwater recharge pilot study is underway in Sonoma Valley. The study, a joint effort of the Sonoma County Water Agency and the City of Sonoma, is exploring groundwater banking as a method for improving local water supply resiliency and restoring aquifer health.

The method of groundwater banking to be studied is also known as “aquifer storage and recovery” and involves storing treated, high quality surface water in underground reservoirs, known as aquifers, during wet periods when surface water is plentiful, and using the water during times of need such as summer months or during droughts.

The groundwater recharge pilot study uses an existing test well located at the Sonoma Veterans Memorial Building property on First Street West. Minor construction to prepare for the study is underway, and it’s anticipated that recharging of wintertime drinking water from the Water Agency’s Russian River facilities into the Sonoma Valley aquifer will begin in March. The purpose of the study is to demonstrate how extra water during the rainy season can be used to recharge the groundwater aquifer and then extracted during times of need.

Construction for the Aquifer Recharge Study
Construction for the Aquifer Recharge Study

“The project is a big step forward in improving the health of Sonoma Valley’s groundwater,” said County Supervisor and Water Agency Board Member Susan Gorin. “If we can use our excess water to offset local groundwater

pumping and recharge depleted aquifers, it will be help our efforts toward sustainable groundwater management in Sonoma Valley.”

Gorin also serves as Chairwoman of the Board of the Sonoma Valley Groundwater Sustainability Agency (GSA), which was formed in 2017. Groundwater banking is one of the tools outlined in California’s Sustainable Groundwater Management Act, which required the creation of the GSA.

“This groundwater banking method has the potential to benefit city residents,” said Sonoma Mayor Madolyn Agrimonti. “If this study works as anticipated, we could someday be using more plentiful wintertime Russian River water to improve the resiliency and reliability of our local water supply, ensuring that groundwater is available during droughts and emergencies.”

“We hope that this is first of many innovative projects that we will see as we implement the Sustainable

Construction for the Aquifer Recharge Study
Construction for the Aquifer Recharge Study

Groundwater Management Act locally,” said Vickie Mulas, a member of the GSA board, who served for several years on the Sonoma Valley Basin Advisory Panel. “This is exactly the type of project needed to advance us toward a sustainable groundwater future.”

The study will include extensive monitoring of water quality and groundwater levels and is being conducted under a permit issued by the San Francisco Bay Regional Water Quality Control Board. Water recovered during the study will be added to a nearby drainage ditch which flows into Fryer Creek. No changes in water quality associated with the testing program will be experienced by Sonoma residents.

Minor construction to prepare for the study is underway by the City of Sonoma Public Works Department Water Team, so that water can be both recharged into and pumped out of the ground over the approximate four month duration of the study. The study is planned and overseen by GEI Consultants Inc. and Pueblo Water Resources, Inc. under contract with the Sonoma County Water Agency, with the City of Sonoma contributing funding for technical and construction support. Neighbors and visitors near the site may see people collecting measurements and samples from the test well and nearby wells during the study.

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