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News: 08/01/2020

Concerns aired at groundwater public hearing

Group working on future of Sonoma Valley’s water supply looking for input, ideas

The year 2042 may seem distant, but in the world of planning for future water supplies, 22 years is a drop in the bucket – a bucket local planners hope will be full of clean water when it arrives.

“People are concerned about potential groundwater depletion,” Ann DuBay said, reflecting on opinions voiced at a virtual public outreach meeting held on Monday, July 20. More than 30 people tuned in to learn about and discuss the work of the Sonoma Valley Groundwater Sustainability Agency (SVGWA), charged by state law with coming up with a groundwater management plan (GMP) to ensure the local water is clean and abundant by 2042.

“Several people indicated concerns with their own wells,” she said, noting that they live in areas where groundwater levels fluctuate or they have had to drill new wells.

“Some folks who live in the southernmost part of the basin had concerns with saltwater intrusion. A few people expressed concerns about new, deep wells and large water users, and the impacts on their own wells,” DuBay added. She is the SVGWA administrator as well as the Community & Government Affairs Manager for the Sonoma County Water Agency.

An uncertain future for fresh water supplies became a hot public topic in the early 2000s with verified land subsidence of up to 20 feet in the California’s heavily irrigated Central Valley, saltwater intrusion into aquifers near the Bay where former hay fields were converted to water-intensive agriculture, as well as continued fresh water demands from population growth.

California passed the Sustainable Groundwater Management Act (SGMA – usually called ‘Sigma’) in 2014, requiring identified problem areas to develop groundwater sustainability plans by 2022 that will be measurably effective by 2042. To get there, the law also enabled special local agencies to forge these long-term management plans with advice from local stakeholders.

Sigma requires at-risk groundwater basins to form groundwater sustainability agencies (GSAs) to manage groundwater and requires them to create and adopt groundwater sustainability plans (GSPs).

Three of Sonoma County’s 14 groundwater basins were designated at risk of failing if corrections are not made: Sonoma Valley, Petaluma, and Santa Rosa Plain. All now have GSAs developing management plans that must be adopted by the end of next year.

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 (SCWA or Sonoma Water, as current marketing would have it) formed the Sonoma Valley GSA at the start of the 2017-2018 fiscal year.

Groundwater agencies are formed by public entities and are themselves public entities, separate from their sponsors. Like a private LLC, they are liable for their own debts, not the parent agencies.

Member districts and agencies have each committed funding, ranging from $20,000 to $117,000 for the first year.

“We have a number of grants defraying a lot of the costs of developing our plan,” DuBay said, “but there will need to be some funding mechanism in the future to implement (the plan). The Santa Rosa Plain GSA has a fee structure set up in their basin. We will likely look at that in the future.”

A 2018 rate study process report can be seen at The authors looked at regulatory fees, service fees, and possibly a parcel tax. The report was prepared by Raftelis Financial Consultants, Inc., of Oakland.

DuBay said that while each (Sonoma County) groundwater basin received a $1 million grant from Proposition 1 (drought relief fund), the member agencies paid for the legal, administrative, meetings, insurance, office costs, etc., of setting up their GSAs. Another $1 million came to each GSA from Prop. 68, she said, with more than half underwriting construction of four new deep monitoring wells, and a geophysical pilot study.

“Another chunk will go to working on better data regarding wells and water use, and a third chunk will go to rural community engagement, to find out the issues and concerns that rural landowners and residents have regarding groundwater and to help the GSA educate people about sustainable groundwater management,” DuBay said.

While a typical watershed includes all the water flowing into an area, coursing down from the surrounding hills and mountains, groundwater is generally found under the level parts of land. The groundwater is designated as a ‘sub-basin’ of the larger watershed basin. Sonoma Valley’s groundwater sub-basin can be readily understood from the SVGSA’s website at

In all, the sub-basin covers about 43,000 acres running from two miles south of Kenwood through Glen Ellen, Boyes Hot Springs, El Verano and Sonoma to the Bay.

“It’s a blend of urban, agricultural and natural lands,” Marcus Trotta said. A hydro-geologist for Sonoma Water, Trotta presented background and findings at the meeting. “Much of it has been used for irrigated agriculture, with vineyards dominating the agriculture.”

Groundwater provides 59 percent of the fresh water in the Valley, with the Russian River supplying 26 percent, mostly to people living in and around the City of Sonoma. Surface and recycled water supply the remaining 15 percent, according to Trotta.

From 1974 to 2012, the combined residential, industrial and business uses increased from eight percent of the Valley’s area to 13 percent. Agriculture increased from 14 to 23 percent of the land area. And while native vegetation dropped from 54 percent to 38 percent during that period, it bounced back to 43 percent by 2012 because of major wetlands restoration efforts in the south part of the county.

The major elements impacting groundwater are lack of recharge (water being pumped out faster than it is replenished), and contamination from surface sources seeping into both shallow and deep aquifers, which can take many years to replenish.

“The Valley gets most of its water from one or two heavy storms a year,” Trotta noted, a lot of which can be lost to runoff. Climate change, mostly drought, has contributed to lower rainfall averages over the past 12 years, dropping from 25 inches a year to 22 inches.

So far, only two areas in the basin have shown persistent declines and there has been no permanent land subsidence. Fortunately, there have been “limited water quality issues,” he noted.

“Some wells in El Verano are pretty bad,” Trotta said, talking about fluctuations in shallow aquifer well water depths over the past decade. They have dropped from .5 to 2 feet. There are even more losses from the deep aquifer, “primarily due to agricultural and rural domestic pumping,” and the declines in two areas are accelerating, he said.

Saltwater intrusions have been found close to the City of Sonoma, though it seems fairly stable for the moment. According to Trotta, “Wells along Highway 37 show higher concentration of chlorides and solutes.” And while nothing north of Highway 121 seems to be showing increasing problems, “there is not enough monitoring to understand the connection.”

Ideas presented at the breakout groups included monitoring and/or metering and regulations to prevent further depletion; possible land use changes which would be accomplished through General Plan modifications or other methods (not by the GSA); finding new ways to recharge groundwater; increasing water conservation; and improved and expanded storm water recapture.

The GSA will hold another public meeting in late fall or winter to discuss future scenarios and draft sustainable management criteria, DuBay said. In 2021, the GSA will be working on projects and management actions that might be needed to meet and maintain sustainability for groundwater levels, groundwater storage, water quality, seawater intrusion, land subsidence, and interconnected surface water.


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Community Calendar

Plan Bay Area 2050 Workshop
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Creekside Nature Hike
Sonoma Valley Mentoring Alliance Fundraiser
Forest Therapy
Economic Recovery town hall meeting