Small scale soil-moisture variability estimated using ground penetrating radar

This paper describes development of Ground Penetrating Radar (GPR) techniques for spatially distributed measurement of soil moisture. Traditional measurement techniques are limited; most significantly they are time consuming, invasive and destructive techniques. Measurement with GPR is non-invasive and rapid. This paper investigates the relationship between a number of properties of the GPR signal and Volumetric Moisture Content (VMC). Using a series of controlled laboratory experiments the two most reliable methods were found to be the signal amplitude and amplitude spectra approaches. Significant relationships were found between maximum amplitude and VMC for a variety of earth materials and situations. Quantitative correspondence between the GPR and invasive measurements of moisture is poor due to differences in sampled area, depth of investigation and the impact of rock fragment content on the relationship between soil water and soil volumetric moisture content. In addition GPR specific errors are introduced by coupling of the radar with the ground surface, and the impact of the profile variability on the GPR signal return.