outdoor scene with blue sky showing trucks and equipment behind a temporary fence with a mud-rotary drilling rig in action at a monitoring well site in Petaluma Valley.

A mud-rotary drilling rig in action at a monitoring well site in Petaluma Valley

A big challenge with managing groundwater is that it’s invisible to the human eye. Unlike surface water in lakes and rivers, we can’t actually see groundwater levels rise and fall. That’s why monitoring wells are so important: These wells are drilled for the sole purpose of “showing” us what’s happening in local aquifers. Through three Proposition 68 grants funded by the California Department of Water Resources (DWR), nine new multilevel groundwater monitoring wells (GMWs) were recently constructed by the Sonoma Valley, Petaluma Valley, and Santa Rosa Plain Groundwater Sustainability Agencies.

Sonoma Water oversaw the construction of  the wells, which expanded the monitoring networks of the Sonoma Valley and Santa Rosa Plain Subbasins and the Petaluma Valley Groundwater Basin. These GMWs expand on the existing monitoring networks, filling critical data gaps regarding groundwater levels, interconnected surface water, and seawater intrusion, as the region works to track progress toward achieving the Groundwater Sustainability Plan (GSP) goal of sustainable groundwater management by 2040.

Sustainable groundwater management is avoidance of undesirable results for six sustainability indicators:

  • Lowering of Ground Water Levels
  • Seawater Intrusion
  • Land Subsidence
  • Reduction of Storage
  • Degraded Quality
  • Surface Water Depletion
outdoor scene showing four black metal pipes standing upright out of the dirt with a larger yellow metal pipe in the center which is mounted in a concrete surface

A completed multilevel monitoring well in Sonoma Valley

Data collected will provide information from shallow and deep aquifer systems. The new wells range in depth from 50 feet below ground surface at one of the Santa Rosa Plain wells, to the deepest one in Petaluma at 505 feet. The GMWs will help track seasonal fluctuations in groundwater levels and quantify annual changes in water budget components.

“The geologic information obtained during the drilling of these monitoring wells has been very helpful in improving the conceptual models of the basins, and the wells will continue to provide valuable high-resolution data to the GSAs and stakeholders over at least the next 20 years, “ said  Mitch Buttress, hydrogeologist with Sonoma Water

The GMWs were constructed between May and September 2022 in the three basins.  The monitoring wells have been instrumented with dataloggers to remotely collect water-level and temperature data on an hourly basis. The GSA’s will upload this data to DWR’s SGMA Portal where it can be viewed by the public.