September 19, 2021
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Monitoring wells provide picture of underground water

November 15, 2019

 During the months of October and November, up to 21 groundwater monitoring wells will be drilled near Sonoma County creeks to provide new information to managers and the public on the link between groundwater and stream flows. Coordination and construction of the wells are a technical service provided by the California Department of Water Resources (DWR) to Sonoma County’s three Groundwater Sustainability Agencies (GSAs).

 Each well will be about 50 feet deep and will be designed specifically for measuring water levels throughout the year. These measurements, when paired with information about the water flowing in nearby streams, help paint a picture of the link between groundwater aquifers and the surface water in creeks, streams and rivers.

“We can’t see what’s beneath the surface, so these monitoring wells act like underground telescopes. They can help us see how much and when water is available,” said Sonoma County Supervisor Susan Gorin, who serves as the chair of the Sonoma Valley GSA.

The connection between groundwater and surface water is an important component of the Groundwater Sustainability Plans that are being prepared by Petaluma Valley, Santa Rosa Plain and Sonoma Valley GSAs. The state-required plans must determine if groundwater pumping is resulting in the loss of water in streams that support endangered and threatened fish and other species.

“These wells will help us better understand the link between specific streams and aquifers so we can make informed decisions about how to protect fish, other wildlife and plants during future droughts and in our changing climate,” said Sonoma County Supervisor Lynda Hopkins, who is Chair of the Santa Rosa Plain GSA.

The monitoring wells are installed by drilling holes that are about eight inches in diameter, until water is reached (around 50 feet). A narrow (2 ½ inch) slotted PVC pipe is fitted into the hole, which is then capped. The wells will then be monitored by GSA staff using instrumentation provided by DWR to track water levels and temperature throughout the year and compared with data from nearby surface water gauges. Each well costs approximately $15,000 to construct and develop. These costs are being paid for by DWR through its Technical Support Services program. DWR has also provided financial assistance in the form of planning grants to help these local agencies develop their GSPs.

“The well drilling will cost DWR more than $300,000 that otherwise would have been paid by local agencies. This is big boon to our community and the information provided will be invaluable,” said Sonoma County Supervisor David Rabbitt, who chairs the Petaluma Valley GSA.

DWR Deputy Director Taryn Ravazzini said, “DWR is committed to helping local water managers succeed in their efforts to sustainably manage the state’s groundwater basins. Through DWR technical support services such as those pursued by Sonoma County’s GSAs, tangible progress can be made toward ensuring a resilient water supply future.”

The wells will be constructed in various locations, including parking lots, vineyards, on road shoulders, creek paths and other publicly owned land. Each well is slated to take less than one day to construct and disruption from construction activities will be minimal. For more information about local groundwater go to;;