Noninvasive water content and electrical conductivity laboratory measurements using time domain reflectometry

A noninvasive approach for measurements of near-surface water content (thet a) and bulk electrical conductivity (sigma(a)) using time domain reflectome try (TDR) is presented. In this approach, an ordinary three-rod TDR probe i s used together with a polyvinyl chloride (PVC) surface block that surround s half the measurement volume. Theoretical and experimental results show th at an analytical solution of the apparent dielectric constant K-a and the s igma(a) of the soil is possible, Thus, the suggested technique does not req uire a separate calibration of the relationship between the measured effect ive K-a and K-a of the soil. The variability of the measurements was shown to be slightly higher than using the traditional approach. The spatial sens itivity of the suggested technique was also investigated. It was shown that using a three-rod TDR probe with a rod spacing of 0.05 m allows the theta and sigma(a) to be measured in the uppermost 2 cm of the soil.