Electromagnetic Investigation of High-salinity Groundwater Zones in Coastal Plains-A Case Study of the Kujukuri Coastal Plain-

Abstract

Estimating saline water intrusion into aquifers in coastal plains has been becoming an im- portant subject in terms of site characterization for the geological disposal of radioactive waste. In addition, delineating the distribution of high-salinity groundwater zones is valuable when us- ing groundwater for municipal, industrial, and agricultural purposes . Conventionally, the elec- trical conductivity of groundwater is measured in hydrogeological surveys to estimate salinity concentration. However, if there are no boreholes available, electrical and electromagnetic explo- ration methods are employed. In such cases, a qualitative hydrogeological interpretation mated electrical resistivity or conductivity distribution transport of salinity, a quantitative of esti- is usually made. To simulate the future estimation of the current salinity distribution is essential. In this paper, first I review electromagnetic methods and electrical conductivity of formation and pore water as a function of salinity concentration. Secondly, I introduce a case study of an elec- tromagnetic investigation in the Kujukuri coastal plain, eastern Japan and evaluate the equiva- lent NaCl concentration of pore water from formation resistivity values obtained from the elec- tromagnetic investigation.