Plan to conserve, improve groundwater resources moves forward
Questions raised at Oct. 12 public meeting about metering, regulation, and climate
By Jay Gamel
Along-anticipated, statemandated plan to turn around continuing losses of Sonoma Valley groundwater will soon be put into action, with a five-year initial program. The extent and seriousness of the overall water situation in California, and in Sonoma County in particular, is evident in the extensive and exhaustive studies and planning that have been moving forward for the past two decades, particularly with groundwater.
Groundwater is vital to Sonoma Valley. Studies show that more than half the water used here comes from wells. The second largest source is water imported from the Russian River, with recycled and local surface water making up the rest.
Sonoma Valley, Santa Rosa, and Petaluma are three specific groundwater sub-basins targeted by the State of California to assess and analyze groundwater conditions and come up with plans to improve problem areas. Sonoma Valley is losing groundwater resources every year, has possible saltwater intrusions coming from the bay, has indications of land subsidence, and unpredictable future rainfall in an evolving environmental situation.
The Sonoma Valley Groundwater Sustainability Agency’s (GSA’s) Sustainability Plan was discussed at a public meeting on Oct. 12.
“The (plans) are a road map for achieving sustainability in the basins within 20 years, taking into consideration climate change, population growth, and land use changes,” Sonoma County Supervisor Susan Gorin, chair of the Sonoma Valley GSA, said. “When implemented, these plans will help protect people and the environment from the effects of groundwater over-pumping.”
Since concern over water resources began developing in the late 1990s, Sonoma Valley has experienced significant population growth and major increases in agriculture, primarily vineyards. These changes have increased demands on all water resources. Groundwater levels have been declining in many areas of the Valley for decades, according to the SVGSA findings.
The plan identifies two groundwater aquifers in the Valley: one shallow (0 to 200 feet deep) and the other deep (more than 200 feet in depth). While the shallow aquifer’s recharging seems to work for the most part, the deep aquifer takes a long time to recover, a vital detail considering most of the groundwater extracted comes from that source.
“Deep-zone aquifers have also declined over the past decade, and do not recover during wet years according to monitoring wells and stream level observations,” the GSA research reports. “These chronic declines indicate that groundwater withdrawals are occurring at a higher rate than recharge or replenishment.”
Possible solutions include metering wells, fees, and mandatory regulations. For now, however, none of these actions are being considered.
“It is possible, if the GSA board determines the need to comply with SGMA [the Sustainable Groundwater Management Act], commercial and agricultural wells could be metered,” James Jasperse told those attending the virtual meeting. Jasperse is the chief engineer and director of groundwater management for Sonoma Water.
Residential well owners are completely exempt if they draw less than 1,785 gallons a day, considerably more than average usage, Jasperse said.
The lack of data on groundwater has necessitated extensive research and analysis since this specific process got underway, back in 2006, with a U.S. Geological Survey groundwater survey. Even after decades and millions of dollars in studies, much remains to be understood about groundwater.
“Due to a lack of data, it is unclear how groundwater pumping affects streams and seawater intrusion,” the presenters concluded.
“We can only make 50-year forecasts based on best available information and reasoned assumptions, with land use and climate being the largest variables,” Jasperse responded to a question about which of many possible climate models were chosen for this plan.
“That is why our approach is to update at least every five years as we move forward. We believe that the climate models will continue to improve. Forecasts of land use, of course, mainly follow policy decisions.”
The Groundwater Sustainability Plan for Sonoma Valley runs an exhaustive 957 pages, and includes detailed appendices. It can be examined online at sonomavalleygroundwater. org, and hard copies are available at Sonoma Valley Regional Library, 755 W. Napa St., Sonoma.
The plan is scheduled to be approved by the Sonoma County Board of Supervisors by January, 2022, and will be forwarded to the California Water Resources Board for final acceptance.