An automated GPR data-collection system was constructed to monitor dynamic hydrologic processes with high spatiotemporal resolution. The design of the system allows for fast acquisition of constant-offset profiles (COP) and common-midpoint surveys (CMP) to monitor unsaturated flow at multiple locations. A fast and accurate motion-control system enables the high-resolution monitoring of spatial patterns of reflectors through time while preserving important information about the normal moveout of reflectors for velocity analysis. In two experiments, infiltration was monitored using time-lapse ground-penetrating radar (GPR) measurements in two and three dimensions. The data from both experiments provide substantial qualitative insight about the dynamics of hydrologic events and a path forward for quantitative analysis of surface-based GPR monitoring data. Analysis shows (1) the advantages of collecting high-resolution time-lapse data, (2) the complexities of patterns associated with the wetting of the soil, and (3) evidence of nonuniform propagation of a wetting front through the soil column.

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