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News: 04/01/2019

Focus is on wells as groundwater board does its research

Replenishing groundwater a priority

Parts of Sonoma Valley, particularly southeast of the city of Sonoma and in the El Verano/Fowler Creek areas, have seen a persistent decline in groundwater levels over the last decade – and it may be expanding. These chronic declines, based on data from the USGS and the Sonoma County Water Agency, indicate that groundwater withdrawals are occurring at a rate exceeding the rate of replenishment within the deeper aquifer zones of southern Sonoma Valley. Saltwater intrusion is also threatening to compromise groundwater quality at Sonoma’s southernmost tip.

State legislation, known as the Sustainable Groundwater Management Act, requires Groundwater Sustainability Agencies (GSAs) in groundwater basins across California to develop sustainability plans over the next three years. One of the Sonoma Valley GSA’s looming questions is, “How do we halt this decline?” The six-member Sonoma Valley GSA Board is made up of representatives from the Sonoma Resource Conservation District, the North Bay Water District, the City of Sonoma, the Valley of the Moon Water District, the County of Sonoma, and the Sonoma County Water Agency, and its purview covers the approximately 44,000-acre groundwater basin on the valley floor extending from San Pablo Bay northward to about two miles south of Kenwood, bounded on the west by the Sonoma Mountains and on the east by the Mayacamas Mountains. While Kenwood is in its own groundwater basin (and not required to develop a sustainability plan), studies have shown the two basins to be hydrologically connected, and the Sonoma Valley GSA’s sustainability plan will most likely take that into account.

Residential and commercial land use and irrigated agriculture have been steadily increasing in the Sonoma basin, as documented by land use mapping over the past several decades. Lands used for irrigated agriculture increased from 14 percent in 1974 to about 23 percent in 2012. Between 1974 and 1993, combined residential, commercial, and industrial uses constituted about 8 percent of the basin. After 1993, these uses increased to about 13 percent. Computer modeling prior to 2017 has simulated average annual losses of groundwater in storage ranging from approximately 660 to 1,400 acre-feet per year, although this number, based on older data, is expected to be refined and updated as the GSA moves forward.

What kind of measures might the GSA take to help slow, and possibly reverse, this declining trend? Results from a recent water storage and recovery feasibility study at a test well near the Sonoma Veterans Memorial Building have proved promising, showing that treated drinking water from the Sonoma aqueduct (which supplies 75 percent of the valley’s drinking water from the Russian River) can be injected underground, mixed with groundwater, and pumped out again, while staying within regulatory thresholds.

“These projects may be a strategy to help stop aquifer decline in certain areas,” said Marcus Trotta at the March 25 meeting of the GSA Board. Trotta is a hydrogeologist with the Sonoma County Water Agency, which spearheaded the study. However, it would most likely be one facet of a multi-pronged approach, along with ideas such as conservation incentives or encouraging actions such as turf removal, he said. Next steps include additional pilot studies in other areas around the basin and looking at the cost of infrastructure needed to get the stored water to places experiencing the groundwater declines (the water pipeline network doesn’t reach those areas).

Well monitoring, registration on the table

Also at the meeting, the board approved its 2019-2020 operating budget, earmarking $30,000 for a well registration program, although whether the GSA chooses to move forward with one has yet to be decided – and likely won’t be discussed until some time next year.

When the GSA’s advisory committee and other technical staff bring a draft of the complete Groundwater Sustainability Plan (GSP) before the GSA Board for approval, expected by December 2021, there will likely be a series of options – and costs – that the GSA Board will be asked to choose between. Director Vickie Mulas asked the board to be cognizant about transparency and public outreach during the development of its GSP.

In the Santa Rosa Plain groundwater basin, stretching from Rohnert Park to north of Windsor, west to Sebastopol and into Santa Rosa to Montgomery Drive and Summerfield Lane, its GSA has gone ahead with plans to charge a fee to groundwater users based on usage, resulting in ire from some residents, and several standing-room-only public meetings. On April 11, the Santa Rosa GSA will meet to formally adopt its fee program and the Sonoma Valley GSA will be watching the results very closely. The Sonoma Valley GSA halted its own exploration of a fee program last year, in order to gather more data, and plans to discuss a new rate fee study by 2021.

In the interim, the Sonoma GSA is working to collect more data on the number of wells and well permits in the Sonoma basin, as 60 percent of all water demands are estimated to be met by local groundwater. Imported water (from the Russian River via the Sonoma aqueduct), surface water, and recycled water supplement that. In February, the GSA’s Advisory Committee created an ad hoc committee to review specifically how wells are permitted in areas experiencing groundwater depletion and the adjacent area of saline intrusion, with the goal of considering some sort of well permitting process modification in those areas. Committee members have expressed concern that new wells in zones of depletion and seawater intrusion could exacerbate the existing problem – and it could become worse in the three years before the GSP is adopted. The ad hoc committee met with Permit Sonoma staff in March.

Permit Sonoma administers all permits for wells within both unincorporated and incorporated areas of the groundwater basin (and the county as a whole). Most water wells are permitted through a ministerial process, but discretionary applications are required in certain hydrogeological areas. Discretionary permits require hydrogeologic reports and sometimes an aquifer pumping test to establish the availability of an adequate water supply. Last year, preliminary data showed there are about 12,487 taxable parcels in the basin, but only about 1,706 known wells. To complicate matters, many wells dug before the 1970s are not permitted.

Permit Sonoma also reviews all development proposals within unincorporated areas that will rely on wells for water supply, including wineries, subdivisions and cannabis permits. While the GSA has no legal authority to review development projects, First District Supervisor and GSA Board Chair Susan Gorin expressed interest in further defining the GSA’s interaction with advisory agencies like the Sonoma Valley Citizens Advisory Commission or the newly formed Municipal Advisory Committee in the Springs area. Under state law, GSAs do have the authority to conduct studies, register and monitor wells, set well spacing requirements, require extraction reporting, regulate extractions, implement capital projects, and assess fees to cover costs.

The GSA plans to host a public workshop on the GSP early this fall, and another in 2020. GSA Board meetings are always open to the public.

The next board meeting will be held on May 20, 4-6 p.m., in Valley of the Moon Water District’s Board Room, 19039 Bay St., Sonoma. Visit for more information and past meeting minutes.

Sarah Phelps is an editor and reporter. She was raised in Kenwood and has a BA from Loyola Marymount University.

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