Water districts race to protect groundwater amid drought

The largest declines in groundwater can be seen in the areas of the El Verano and Eighth Street East.|

Sonoma Water held its first town hall this month, part of a new series to review the ongoing drought, local water conservation measures and guidelines for well users.

Groundwater in the Sonoma Valley basin has declined approximately 900 acres of water per year from 2012 to 2018, fueled in part by the drought and a “general upward trend in groundwater use,” according to Ann Dubay, the administrator of the Sonoma Valley Groundwater Sustainability Agency.

The local water basin is approximately 44,000 acres, and its groundwater makes up just over half of the water used in Sonoma Valley, Dubay said. Due to less reliable rainfall over the past decade, the SVGA has started planning projects designed to sustain the region’s remaining groundwater.

There are four sources of water for residents of Sonoma Valley: groundwater through wells, transported water from the Russian River watershed, recycled water from waste that is purified, and surface water from rivers and streams.

Streams and small ponds have dried up during stretches of drought in recent years. The largest declines in groundwater can be seen in the areas of the El Verano and Eighth Street East, Dubay said, where a deep aquifer is losing water quicker than other parts of the region.

“The declines are in the deeper aquifer, that means the aquifer that's greater than 200 feet deep, is where we're seeing issues,” Dubay said. “And that is much older water it takes a lot longer for water to get down into that really deep aquifer.”

The deep aquifer is of concern because it takes longer to recharge than shallow ones. This could be a problem in the near future as drought conditions continue to plague California, forcing residents to use greater amounts of groundwater to supplement other sources, according to Christopher Watt, the senior engineering geologist for the North Coast Regional Water Board.

“As we see changes in the availability and surface of water, there's definitely going to be a higher demand on groundwater,” Watt said in the June 2 town hall. “And that only increases the need to make sure that the quality can serve all of its beneficial uses.”

Declines in the aquifers in El Verano and Eighth Street East are likely caused by local wells being pumped , Dubay said, however it’s unclear which wells or users are responsible for the decline. Piecing together information about how the hydrology system of Sonoma Valley functions will be key for the Sonoma Valley Groundwater Sustainability Agency’s plans in the coming decade.

“Are we having problems with seawater coming into the basin down near San Pablo Bay because of pumping groundwater? We don't think we're having problems,” Dubay said, “but we don't know for sure because we don't have very good measurements down there.”

The next five years will be used to fill in those “data gaps” and to plan for and engineer projects to help sustain the groundwater of Sonoma Valley. Questions remain about how groundwater pumping affects Sonoma Creek and the animals that need it for water and breeding, Dubay said.

Some of the initiatives to protect groundwater and replenish the aquifer are already underway.

Last year the state water board called for a 20% reduction of water use by all residents of Sonoma County; Valley of the Moon Water District customers exceeded that mark with a 26% reduction in 2021 compared to the previous year, said General Manager Matt Fullner. The Valley of the Moon Water District has also been approved for $3 million in Drought Relief Project funds from California Department of Water Resources to create two aquifer storage and recovery wells, Fullner said.

Two existing wells in will be repaired and evaluated for aquifer storage and recovery. If the wells can be retrofitted for aquifer storage and replacement, Fullner said the amount of water that can be put into the well is “roughly half of the production capability of the well.”

“So whatever the well can produce from the ground, about half of that can be put back in the ground,” he said.

In addition to mitigation measures for water use and water loss, actions to create a more sustainable groundwater system help protect the long-term future of Sonoma Valley’s source of water.

“If you've got a sustainable groundwater basin that is not being overdrafted each and every year,” Fullner said. “When you do run into drought conditions that last for a year or two, it's essentially a battery that you've charged up over time that you can then draw on to help you get through times of extreme drought.”

Contact Chase Hunter at chase.hunter@sonomanews.com and follow @Chase_HunterB on Twitter.

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