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.
Filling data gaps in the monitoring network for each of Sonoma County’s principal aquifers is considered a high priority data need to successfully implement the Sonoma Valley Groundwater Sustainability Plan (GSP). You can think of the GSP as our road map that defines projects, actions and a schedule to use, protect and sustain our groundwater resources. One of the key projects within the Sonoma Valley GSP is to create a system that monitors groundwater levels. This system is known as the Sonoma Valley Well Monitoring Network. Our network will help us understand how groundwater levels change over time and across different locations throughout the basin. Data collected will provide information from shallow and deep aquifer systems, and will help track seasonal and annual fluctuations in groundwater levels.
Since the GSA was formed, the agency has been expanding the monitoring well network through GSA owned wells, partner agency wells, and voluntary private wells. However, data gaps still exist in several portions of the basin.
Update – Fall 2022
In 2022, with funding from the California Department of Water Resources Proposition 68 grant, three new multilevel groundwater monitoring wells (GMWs) were constructed by the GSA. These GMWs expand on the existing monitoring network, filling critical data gaps regarding groundwater levels, saltwater intrusion, and interconnected surface water, as the GSA works to track progress toward achieving the Groundwater Sustainability Plan goal of sustainable groundwater management by 2040.
Data collected will provide information from shallow and deep aquifer systems. The new wells range in depth from 110 feet to 465 feet below ground surface. The GMWs will help track seasonal fluctuations in groundwater levels and quantify annual changes in water budget components. The monitoring wells have been instrumented with dataloggers to remotely collect water-level and temperature data on an hourly basis.
Read the full report on the new monitoring wells here.
Update – August 2024
In 2023, the GSA was awarded grant funding to construct four deep multi-level monitoring wells that will be between 300 to 500 feet deep to evaluate groundwater levels and assess seawater intrusion. The wells will be instrumented with dataloggers to remotely collect water-level 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. “The geologic information obtained during the drilling process has been very helpful in improving the 3-D models of the basin, and the wells will continue to provide valuable high-resolution data to the GSAs and stakeholders over at least the next 20 years” explains Mitch Buttress, hydrogeologist with Sonoma Water.
The groundwater monitoring well project will expand on the existing monitoring networks, filling critical data gaps regarding groundwater levels and interconnected surface water as the region works to track progress toward continued sustainable use of our groundwater. The wells will be constructed in 2025.
Update – March 2026
In February 2026, the GSA finished construction of the last of our grant-funded monitoring wells. Since 2024, three sea water intrusion and three deep multi-level monitoring wells were installed across the Sonoma Valley basin, filling critical data gaps regarding groundwater levels, saltwater intrusion, and interconnected surface water. The monitoring wells have been instrumented with dataloggers to remotely collect water-level and temperature data on an hourly basis.
Read the full report on the new monitoring wells here.