To flow through an image: Advances in the use of ground-penetrating radar in hydrology inspired by the vision and work of Rosemary Knight

More than two decades ago, Rosemary Knight asked her graduate students to imagine how we might make groundwater “flow through an image” collected using ground-penetrating radar (GPR). This simple statement has behind it profound questions that require deep understanding of the fundamental nature of GPR and its ability to capture the structure, properties, and processes controlling subsurface flow and transport. The work that Dr. Knight started back then has matured in these three areas, i.e., estimation of structure, properties, and processes, to create unique branches of inquiry.