Use of vertical electrical soundings to delineate seawater intrusion in a coastal area of Byunsan,Korea |
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| Authors: | Sung-Ho Song Jin-Yong Lee Namsik Park |
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| Institution: | (1) Rural Research Institute, Korea Rural Community and Agriculture Corporation, Ansan, 425-170, South Korea;(2) GeoGreen21 Co., Ltd., 4th Floor, SEK Building, 1687-22, Bongchon6-dong, Gwanak-gu, Seoul, 151-812, South Korea;(3) Division of Civil and Ocean Engineering, Dong-A University, 840 Hadan2-dong, Saha-gu, Busan, 604-714, South Korea |
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| Abstract: | To delineate spatial extent of seawater intrusion in a small experimental watershed in the coastal area of Byunsan, Korea,
electrical resistivity surveys with some evaluation core drillings and chemical analysis of groundwaters were conducted. The
vertical electrical sounding (VES) method was applied, which is useful to identify variations in electrical characteristics
of layered aquifers. The drilling logs identified a three-layered subsurface including reclamation soil, weathered layer and
relatively fresh sedimentary bedrock. The upper two layers are the main water-bearing units in this area. A total of 30 electrical
sounding curves corresponded mostly to the H type and they were further divided into three classes: highly conductive, intermediate,
and low conductive, according to the observed resistivity values of the most conductive weathered layer. In addition, groundwater
samples from 15 shallow monitoring wells were analyzed and thus grouped into two types based on HCO3/Cl and Ca/Na molar ratios with TDS levels, which differentiated groundwaters affected by seawater intrusion from those not
or less affected. According to relationships between the three classes of the sounding curves and groundwater chemistry, locations
of the monitoring wells with low HCO3/Cl and Ca/Na ionic ratios coincided with the area showing the highly conductive type curve, while those with the high ratios
corresponded to the area showing low conductive curve type. Both the low electrical resistivity and the low ionic ratios indicated
effects of seawater intrusion. From this study, it was demonstrated that the VES would be useful to delineate seawater intrusion
in coastal areas. |
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| Keywords: | Seawater intrusion Vertical electric sounding Resistivity Ionic ratio Korea |
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