Sonoma County GSA Planning Process Ramps Up to Address Sustainability Concerns

Written By: Gary Quackenbush
Published: March 5, 2020

The plan development process that began in 2018 is halfway toward the state deadline set for June 31, 2022, as Groundwater Sustainability Agencies (GSA) focus on defining exactly what sustainability management should look like in the three Sonoma County basins – the Santa Rosa Plain, Petaluma Valley and Sonoma Valley.

Public workshops will continue as key milestones are achieved for technical work performed to date, and an online survey is planned in 2020 to gather public input.

“At the heart of the GSA planning process is the ability to determine and identify what sustainability means,” according to Ann DuBay, Administrator for the Sonoma Valley and Petaluma GSAs and community and government affairs manager for the Sonoma County Water Agency (SCWA) providing outreach for all three basin GSAs. “Based on recent fact-finding efforts and ongoing assessments, we want to make a draft plan available for public review within the next 18 months to seek feedback before a final plan is prepared.”

Sustainable Management Criteria

Groundwater Sustainability Plans (GPS) are required from each GSA to address defined sustainability criteria, including undesirable results, measurable objectives and other quantitative goals.  Specific plans must be developed to achieve sustainability during the 20-year life of the plan.

While one of the state’s required criteria does not apply to the Santa Rosa Plain (seawater intrusion) all of California’s six main sustainability indicators all apply to the Petaluma Valley and Sonoma Valley GSAs.

DuBay noted that each Sonoma County GSA has been tentatively approved to receive another $1 million, possibly later this month, from the California Department of Water Resources, to fund drilling and monitoring of deep-water wells. This is in addition to the $1 million already received by each GSA to cover the development of Groundwater Sustainability Plans (GSP).

If received, the new grants will help fund the collection of well data information to be obtained from Permit Sonoma, and will also help finance outreach and research on wells in rural areas of the county-owned by those who may not be affiliated with water-related organizations.

Future sources of GSA funding have yet to be determined to pay for five-year progress reports and ongoing water monitoring efforts agencies have been financing thus far.

The Sustainable Groundwater Management Act (SGMA) does not allow GSAs to monitor rural wells. In the future, a fee based on usage could be assessed, such as is the case with the Santa Rosa Plain GSA that established a groundwater sustainability fee, as authorized by the Water Code Section 10730 and pursuant to Agency Ordinance No. 19-01, in the amount of $19.90 per acre-foot annually.

“While no decision about ongoing GSA funding has been made,” said DuBay, “We will likely start looking at the funding issue during the year ahead. In regard to fees and taxes, our local GSAs will be considering similar types of fees to be as consistent as possible, since people may have land in all three basins, but it is too soon to say what they will be.”

Groundwater User Registration Program

The Santa Rosa Plain GSA will be providing post-card questionnaires to all property owners in unincorporated areas asking for information on wells and groundwater usage to determine what the most appropriate and cost-effective management strategies may be recommended in the future.  The other two Sonoma County GSA basins are not planning similar registration programs at this time.

Information gathered will be used to fill the gaps in the groundwater usage model, which is an important component of the GSP. Participation is voluntary but is encouraged for private well owners to get a better picture of groundwater usage in this basin.

Online Public Survey

While a start date has yet to be announced, DuBay said this year that local GSAs will conduct an online survey directed at those living in the three basins to gain feedback on what is important to them with regard to six sustainability indicators.

“We want people to take a closer look at these factors and tell us what they think. After the survey is completed, we will be holding roundtable discussions to gather more feedback from the public in person to further assess what they want.  This by no means a scientific study, it is a way of asking people to provide us with an overall sense of what they would like to see as outcomes of this GSA management planning process,” DuBay added. “Several individuals have already expressed agriculture-related concerns about water sustainability.”

She explained that the Central Valley relies heavily on groundwater as well as state water project supplies, and while this basin is expected to fully recover over time, it may need other sources besides groundwater for the long term.

The six GSA sustainability indicators include:

  • Groundwater Levels: This is measured by well monitors in combination with historical groundwater data to determine how wells performed during long periods on record. Criteria may vary, but the goal is to assess if water levels are dropping or filling up and trends for the future. The Santa Rosa Plain and Petaluma Valley GSAs are conducting in-depth groundwater studies to update factors specific to each basin’s valley floor.
  • Seawater Intrusion: The goal is to find out if over-pumping of wells has led to this.  While more prevalent in areas near salt or brackish water, such as San Pablo Bay, it can happen in other areas under certain circumstances, such as during a severe drought.
  • Reduction in Water Storage: The amount of groundwater available for human, agriculture and livestock use is directly related to water storage in aquifers as well as dams and reservoirs. This determination can lead to water banking returning water underground through wells.
  • Water Quality: The objective is to preserve and enhance water quality. Sometimes well drilling, for example,  has led to the presence of sulfur and other chemicals. In areas with historical agriculture use, nitrates have been detected in groundwater. Here, again, over-pumping of groundwater can also play a role.
  • Land Subsidence: The question is, are land levels within Sonoma County basin regions dropping or stable?  While this is not a local issue, evidence from the effects of groundwater loss in the Central Valley has raised concerns.
  • Surface Water Depletion: This involves looking at surface water and groundwater interaction. GSAs are trying to determine if groundwater depletion from over pumping is having an impact on surface water, the lack of which can directly affecting Steelhead habitat and migrations as well as marshlands.

DuBay said the GSAs have a contract with the SCWA that has a strong relationship with the USGS in conducting research on all three Sonoma County basins. She said the Petaluma Valley GSA will complete its first groundwater study in the next few months.

The California Department of Water Resources monitors shallow wells and use stream gauges to measure the interaction between ground-and-surface water.

Santa Rosa Plain GSA

“A large focus for our GSA during 2020 is to make substantial progress on a Groundwater Sustainability Plan specifically for the Santa Rosa Plain groundwater sub-basin,” said Andy Rodgers, GSA Administrator, and engineering manager for West Yost Associates.

“This is a complex initiative, primarily funded by a State grant, and spearheaded by our 18-member advisory committee.  During 2020, our committee will be working through determining appropriate sustainable management criteria.  Several public workshops are planned this spring, in addition to monthly GSA meetings.”

The issue of discharging too much water from dams and reservoirs during heavy rainy seasons has some worried that this may also diminish water availability, as was the case prior to 2012 when record storm totals led to discharges that were not followed by sufficient rainfall to replenish above-ground storage.

DuBay said advanced forecasting techniques are now in place to avoid this outcome. In 2019, Lake Mendocino, for example, was managed to hold more water than in the past. She said sophisticated modeling tools are being used by local GSAs today to assess future water supplies for people living in the groundwater basins.

While having a consistent and adequate water supply coming from as far north as Potter Valley does affect agriculture and fish species (Chinook Salmon, etc.) along Dry Creek, as well as Cloverdale, Hopland and Ukiah, DuBay said Sonoma and Marin Counties are “in decent shape given current water storage capacity of Lake Sonoma.”

“We hope people living in Sonoma County’s three GSA basins will sign up to receive monthly email updates by going to one of the websites shown below.  We also hope residents in these county basins are also willing to participate in the upcoming online and email survey as well as attend public workshops.”

For more information about GSA agendas, public meetings, etc., go to:  HTTP:// ; HTTP://  or HTTP://

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