Napa groundwater update: staff seeks voluntary measurement, pilots and incentives after modeling shows limits to small-scale cuts

NAPA, Calif. — County staff and technical consultants presented an annual update Sept. 23 on implementation of the Napa Valley Subbasin Groundwater Sustainability Plan, reporting added monitoring and outreach and asking the board to support more incentives and measurement to preserve groundwater and summer stream flows.

Lede and key point: The county reported new monitoring wells, a state-funded stream-gauge installation program and an expanded ecological-monitoring effort at six intensive sites. Consultants’ modeling showed a 10 percent reduction in groundwater pumping focused near the Napa River’s tributaries produces measurable benefits, but under the drier conditions after 2015 the subbasin could need larger reductions — as much as about 24 percent in the model scenarios — or a combination of reductions and supply augmentation to meet the plan’s sustainability goal.

Why it matters: Napa’s aquifer is shallow and closely connected to surface flows that support fish and other species. The Groundwater Sustainability Plan implementation is intended to keep the county in local control of groundwater management under the state Sustainable Groundwater Management Act (SGMA) and to avoid state intervention.

What staff and consultants said Jamieson Crosby…