<title>Borehole GPR measurement of soil water content during an infiltration experiment</title>

Abstract

Borehole ground penetrating radar (GPR) measurements of water content within the unsaturated zone were performed during infiltration experiments using both a uniform and point source of water at the soil surface. Horizontal GPR antenna access tubes were installed at a depth of 1 m to measure the water content within the horizontal plane underlying the surface water sources. The zero offset profile and multiple offset gather modes of data collection were used to produce velocity profiles and tomograms that were converted to water content. Time domain reflectometry (TDR) probes provided near-surface measurements of water content to complement the deeper borehole GPR data. For the point source, the water content tomograms and profiles showed that the zone of increased water content was restricted to a 1 m diameter zone, centered below the point source. For the uniform source, significant variability in water content within the studied area was observed possible due to preferential flow of water through the soil profile.