Estimation of saline regions using ground-penetrating radar

In order to conserve the groundwater environment nlear 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 sriline regions now, cannot detect the slight displacement of the surface of a fresh and 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 laiwer frequency. We focused on the attenuation of highfrequency component of electromagnetic waves and devised the method for estimating a saline region through the time-frequency aioalysis. In the small scale model with a fresh and saline water bloundary, the effective areas of the low-pass fdter 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 possibiIity of the conductivity mapping with GPR and the saline region detection.