Sonoma Valley deep wells are dropping in two areas, and the groundwater agency is drafting a plan to reduce pumping

By The Downspout · Posted Oct 20, 2026 · 6 min read

The Sonoma Valley groundwater agency's draft five-year review says water levels in deep wells under two areas, El Verano and Eastside, have fallen below its limits. The agency is drafting a plan to reduce pumping, with a draft target of about 15 percent. It starts with incentives and voluntary steps. Limits are a possible later step. Its board hears an update Monday, October 26, 2026, 4 to 6 p.m. No vote on the plan or on any pumping limit is scheduled.

Where it is and what it does

The Sonoma Valley groundwater basin is the underground water supply beneath Sonoma Valley. It sits next to San Pablo Bay. Wells in the valley pump from it.

The Sonoma Valley Groundwater Sustainability Agency, called the GSA here, is the public agency that manages that groundwater. It was formed in June 2017 under a state law called the Sustainable Groundwater Management Act. Its board has directors from the City of Sonoma, the County of Sonoma, and four water and conservation agencies.

The GSA's main document is a 20-year plan. The state approved it on January 26, 2023. Its goal is a basin that is sustainable by 2042. State law says the plan must be reviewed in writing at least every five years. This is the first five-year review. The GSA also calls it the Periodic Evaluation.

The plan sets a lowest allowed water level for each of its monitoring wells. If 20 percent of those wells stay below their lowest level for three years in a row, the plan calls that an "undesirable result." In plain words, water levels are too low.

What happened

Short version: water in the deep layer under two areas has dropped below the plan's limits. The agency is drafting a plan to reduce pumping, starting with incentives and voluntary steps.

The GSA posted the agenda for its board meeting on Monday, October 26, 2026, 4 to 6 p.m. The meeting includes an update on the draft five-year review and on the draft plan to reduce groundwater use. Both are information only. The board does not vote on them.

The draft review says the deep layer of the basin, under two areas, has fallen below its limits. The areas are El Verano and Eastside. The GSA calls them priority areas. In both, levels in deep wells, those deeper than 200 feet, have been dropping for more than a decade. The GSA describes the El Verano area as an oval centered in El Verano, from about Boyes Boulevard to Leveroni Road. It describes the Eastside area as a diamond centered near Napa Road and 8th Street East.

The review says the undesirable result for water levels began in fall 2023. Because levels are used to track the water stored underground, the review says the amount stored is also falling. The review says owners in and near these areas applied for permits for up to 12 replacement or extra wells. It says falling levels likely hurt existing wells.

Not everything is falling. The review says the shallow layer has not had an undesirable result. It says water quality is within limits for nitrate, arsenic and salt. It says seawater is not moving into the basin and the land is not sinking from pumping.

The review says people pump more than the basin can sustain. An acre-foot is the water it takes to cover one acre one foot deep, about 326,000 gallons. The agency estimates the basin can sustain 5,400 acre-feet of pumping a year. From 2021 to 2025, estimated pumping ran between 6,429 and 6,768 acre-feet a year. It was higher in dry years.

In 2025, the GSA's table shows about 3,722 acre-feet pumped for agriculture and about 1,003 for rural homes. The total was 6,429.

The agency's computer model estimates the amount of water stored underground fell by about 1,300 acre-feet a year from 2018 through 2024. If nothing new is done, the model projects a drop of about 800 acre-feet a year.

Because of this, the review says the 20-year plan must be amended. The change would make El Verano and Eastside formal management areas. It would also add a Groundwater Demand Management Plan, meaning a plan to reduce or offset pumping. It is now expected in spring 2027.

The draft demand plan is a work in progress. Staff say about 1,029 acre-feet a year needs to be made up through projects and management actions. A slide also shows an approximate 15 percent pumping reduction target. A consultant, ERA Economics, is drafting the plan. The board hired it on January 26, 2026.

The draft sorts actions into four "action levels," based on how low groundwater levels are. Level 1 is sustainable. Level 4 is when levels stay too low. A slide says current conditions would put Sonoma Valley at level 3.

Level 2 adds water use reporting, benchmarking and water audits.

Level 3 adds incentive programs. They include a structured voluntary reduction in use with a 15 percent target. They also include an expanded Cash for Grass program, water fixture replacement, water-efficient landscape rules and irrigation scheduling.

Level 4 adds mandatory well meters and pumping limits. A slide says these would not start until three years after the board adopts the demand plan. The slide's example timeline has the plan adopted in 2027, level 3 steps from 2027 to 2030, and a check in 2030 or 2031 on whether to move to level 4. That is an example, not a decision.

The draft list of measures for rural homes includes education, water use reporting, water audits, meter cost sharing and pumping limits. None of these has been chosen.

The board will vote on one other item at this meeting. It is adding $220,000 to its technical services contract with Sonoma Water, the county water agency, through September 30, 2027. Staff recommend approval. This vote is not about pumping limits.

What it means for you

Check whether you are near one of the two areas. Start with the water map. Then read who manages groundwater in Sonoma County. The GSA also has a data dashboard with a priority area map.
If you have a deep well, ask your pump company about it. The GSA suggests well owners contact their pump company and know their pump level set point.
Join a free program. The GSA runs Level Up!, where well owners volunteer to have their well water level measured in fall and spring. It also runs Flow Smart, which offers a free professionally installed flow meter. The GSA says the meter is worth $4,500 to $6,000. Call the GSA at (707) 243-8555.
Come to the meeting, or watch the schedule. The October 26 meeting is open to the public. The agenda says each speaker usually gets 3 minutes. The agenda and packet are on the GSA's website.
Pumping limits are only a draft idea so far. Nothing here is decided. Mandatory meters and limits are in the draft only at level 4, and not before three years after the plan is adopted.

What happens next

The board hears the update on October 26. See the place on a map: Valley of the Moon Water District office, El Verano.

The GSA advisory committee reviews comments on the draft review on December 15, 2026. The board hears the final draft on January 25, 2027. The review is due to the state by January 31, 2027. The amendment with the demand plan is expected in spring 2027.

The comment period on the draft review ran September 9 to October 9.

For the neighboring basin, see our post on the Petaluma Valley review.

Where this came from

The Sonoma Valley GSA board agenda and meeting packet for October 26, 2026. They include the staff report on the draft five-year review, its executive summary, the staff report and slides on the demand management plan, and the draft contract change. Background comes from the GSA's home page, priority areas page and periodic evaluation page. Everything about the demand plan and the amendment is a draft or proposal until the board acts.

Sources

Checked 2026-10-20. Rules and programs change. If something here is out of date, the source above wins. Spot an error? See our corrections policy.