干旱区生态环境知识资源中心

Continuous monitoring by time-lapse and repetitive measurements using cross-hole geo-radar was conducted to investigate soil moisture distribution arid migration beneath an infiltration pit for artificial groundwater recharge. This monitoring enabled us to clarify the infiltration process from the infiltration pit into the vadose zone in a quantitative, nondestructive, and noninvasive way. The infiltration pit was 2.0 x 2.0 m square and 23 m deep between 2 boreholes in gravel soil. The groundwater table was at about -10 m. We monitored the vertical distribution of electromagnetic wave traveltime beneath the infiltration pit by repetitive measurements using cross-hole geo-radar profiling with zero-offset gathering. Traveltime was distinctly retarded from the upper layer to the deeper one after ponding of the pit. The downward retardation velocity of the infiltration rate into the soil was estimated at 8 x 10(-2) cm/s. The estimated values for water content and water seepage rate in the soil were almost coincident with the directly measured values. In our case of an infiltration pit test, cross-hole geo-radar monitoring was an efficient, noninvasive method for visualizing the infiltration process and estimating water migration properties of the soil on a macro scale.