Estimation of saline regions using ground-penetrating radar

In order to conserve the groundwater environment near seashore region, it is essential to know the behavior of the interface between fresh and saline water. However, electric exploration, which is the only practical method for measuring saline regions now, cannot detect the slight displacement of the surface of a fresh mod saline groundwater boundary. Thus, we tried to detect the saline region using GPR. Electromagnetic waves propagate peculiarly in the saline region affected by the diffusion process. Also, the frequency distribution of the reflection wave from a conductivity interface transforms into lower frequency. We focused on the attenuation of high-frequency component of electromagnetic waves and devised the method for estimating a saline region through the time-frequency analysis. In the small scale model with a fresh and saline water boundary, the effective areas of the low-pass filter are found to fit the distribution of conductivity. Besides, in the experiment of expanding saline region, records monitored at one point detected the lower change in frequency of the reflection wave from transition zone of water content allow with saline fluctuation. As a concluding remark this research demonstrated the possibility of the conductivity mapping with GPR and the saline region detection.