Napa Valley Joint Surface Water and Groundwater Monitoring

The lack of data on shallow groundwater conditions near key streams in the Napa Valley was recognized as a data gap affecting ongoing efforts to manage groundwater resources sustainably. We provided critical services to facilitate the construction of a new network of dual-completion monitoring wells and surface water monitoring instrumentation to continuously track interaction between surface water and groundwater at five sites in the Napa Valley. Services included:

• Development of a grant proposal to fund construction and early data collection,
• Monitoring well design specifications and drilling contractor bid review support,
• Coordination of daily drilling and well construction activities and
• Development of geologic cross-sections to provide context for groundwater conditions observed at each site.

In the years since construction ended, we have maintained site instrumentation, performed synoptic water quality sampling, and managed data collected by the network.

The monitoring effort has provided new insights into the timing and duration of hydraulic connectivity between streams and groundwater and allows Napa County to inform stakeholders about interactions between surface water and groundwater in an efficient and timely manner.

The results of the monitoring effort informed the hydrogeologic conceptual model of Napa Valley and were critical for the calibration of a numerical groundwater flow model. The monitoring network sites also serve as representative monitoring locations for the Napa Valley Subbasin under the Sustainable Groundwater Management Act.

Significant Project Elements

• Monitoring network design and well specification development
• Monitoring well construction inspection and geologic logging
• Geologic cross section development
• Continuous water level and water quality data collection
• Temporal analysis of hydraulic gradients and water quality conditions
• Reporting and presentation of results to technical and non-technical audiences