oa Advancing Geophysical Methods for Groundwater Evaluation and Management Near surface keynote paper

There is increasing use, throughout the world, of groundwater as the primary source of freshwater. The evaluation and management of this resource requires information about the extent and connectivity of groundwater aquifers, the contained volume of producible water, the changes in stored water, and the processes that can impact the quantity and/or quality of the water. Such information is required at a density of spatial and temporal sampling best provided by various forms of geophysical data. For the past decade, we have been working in partnerships with groundwater districts and managers to advance the use of geophysical methods as a central component of groundwater evaluation and management. Examples include the use of surface and logging nuclear magnetic resonance to estimate water content and hydraulic conductivity, electrical resistivity tomography for imaging saltwater intrusion along the California coast, and satellite InSAR data for estimating changing hydraulic head levels in confined aquifers in the San Luis Valley, Colorado. Such examples illustrate the tremendous potential for - and need for - geophysical methods to ensure the long-term health of our groundwater resources.