Understanding how water moves and interacts in the aquifer is essential to effectively managing our groundwater. One tool that groundwater managers use to understand what is happening in an aquifer is a hydrologic model, which is a simplified conceptual and computer model that helps simulate and predict the use and movement of groundwater. To function properly, these models need accurate local information to base the model assumptions on. With grant funding from the department of water resources, the GSA is currently working to improve the understanding of the aquifer system hydrogeologic framework, distribution, and potential effects of faults on groundwater flow, and basin boundary characteristics through analysis of existing and new geophysical data and strategically designed aquifer testing programs.
One way we assess what our aquifer looks like underground is through aerial electromagnetic (AEM) surveys and checking that the results make sense with ground-based surveys of wells, known as “ground-truthing.” AEM surveys are a relatively new technology that provides valuable insights into what is occurring underground. The process includes flying a helicopter over the land surface that contains the groundwater basin and taking the measurement of how the properties of soil, rocks and water change at different depths below ground surface. The AEM surveys help the GSA understand the existing conditions and potential risks to beneficial groundwater users from groundwater pumping and potential surface water depletion.
The Sonoma Valley GSA is currently in the process of completing four additional miles of ground-based geophysical surveys to fill remaining data gaps and ground-truth the AEM surveys that were conducted by the Department of Water Resources (DWR) in 2022 (More information on DWR’s AEM flights available here). The Sonoma Valley GSA is also performing aquifer tests to evaluate aquifer properties, such as hydraulic conductivity – which is how water moves through the empty spaces within the aquifer.
Additional data gaps that will be filled include:
- Locations and depths of existing water wells and mounts of groundwater pumping;
- Role of faults and geology to groundwater flow and recharge within and along the boundaries of the basin;
- Three-dimensional gaps in the monitoring network for each primary aquifer through installing shallow and deep multi-level monitoring wells
The goal of the project is to improve the GSA’s ability to assess potential impacts from groundwater pumping to beneficial users and improve the GSAs ability to plan for and implement projects and actions needed to maintain sustainable groundwater conditions.