Determination of Spatial and Temporal Variations of Volumetric Soil Water Content Using Ground Penetrating Radar: A Case Study in Thailand

Abstract

In this research, ground penetrating radar (GPR) was used to determine the volumetric soil water content (VSWC) of a loamy soil. The GPR was set up in the ground wave fixed offset me-thod using both 400 and 900 MHz frequency antennae. By estimating the relative dielectric per-mittivity of the soils, these values were converted to the VSWC by Topp’s equation. The gra-vimetrically calculated VSWC values from the soil samples at different depths were used as thereferences. In addition, the ability of the GPR method to detect variation in the VSWC over time was evaluated in three periods spanning the dry and rainy seasons. The VSWC estimated from the400 MHz analysis had a high correlation with the gravimetric method under dry conditions at a soil depth of 10-30 cm and under wet conditions, the result was reasonable at 10-20 cm. In contrast, the 900 MHz derived VSWC estimateswere not related to those from the gravimetric analysis, although the results were reasonable in dry conditions. The VSWC values obtained fromthe 400 MHz antenna give a reasonable estimation of VSWC of this site. Thus, the GPR method is appropriate for estimating the VSWC due to the ease of data acquisition and processing.