ESTIMATION OF HYDRAULIC CONDUCTIVITY USING NEAR-SURFACE GEOPHYSICAL TECHNIQUES

Near-surface hydraulic conductivity is a critical parameter for environmental investigations, agricultural management, and groundwater remediation. Hydraulic conductivity is a spatially heterogeneous variable that is difficult to measure over large areas using conventional point measurements. Although hydraulic conductivity is often estimated using soil texture, these estimates are frequently inaccurate, and soil textures are also difficult to map accurately. In this research, we explore the potential of ground penetrating radar (GPR) and electromagnetic induction (EM) to map hydraulic conductivity in near-surface soils by comparing changes in soil moisture content with time. Data was acquired in an agricultural field using three GPR frequencies before and after a wetting event, and the data was analyzed to determine the near-surface soil moisture. Data was also acquired using a Geonics EM38 to measure electrical conductivity, which was also related to soil moisture. Differences in the soil moisture estimates from these techniques were used to indicate the hydraulic conductivity distribution across the field. Conventional measurements of hydraulic conductivity were also acquired using a guelph permeameter, and the pattern of hydraulic conductivity interpolated from these measurements were compared to those obtained from geophysical data.