Vertical soil moisture dynamics in the vadose zone: A high-resolution GPR reflection study

This paper presents a multi-year field study in which high-frequency 900 MHz reflection traveltime measurements were used to monitor vertical soil moisture distribution in the upper 3.0 m of vadose zone. GPR reflection profiles and common-midpoint (CMP) soundings were collected over the complete annual cycle of soil conditions characterized by numerous wetting, drying and freezing cycles typical of mid-latitude climates. The presence of four distinct stratigraphic reflection events at well-defined depths permitted quantitative assessment of seasonal moisture processes and their temporal dynamics during the study period. The incorporation of direct ground wave measurements from coincidently collected CMP soundings yielded improved resolution at the air-soil interface which facilitated characterization of the hydraulic coupling between shallow and deeper moisture conditions.