Variation Pattern Analysis Of Saltwater-Freshwater Interface In The Coastal Aquifer, Mangsang, Korea

For identification of the saltwater-freshwater interface in the coastal aquifer, many researches have been focused on seawater intrusion by groundwater pumping and have been performed in the way of mathematical model development and numerical modeling. But the investigations about the variations by the change of natural conditions such as tide, rainfall, land wind had been rarely performed. This research is focused on the observation and interpretation of in-situ saltwater-freshwater interface and its temporal variation due to the change of natural conditions. The research has been performed at the beach aquifer of Mangsang in the western side of East Sea. The EC, temperature, pH, and DO had been directly measured in wells. Saltwater-freshwater interface could be identified using EC vertical profiles. EC vertical profiles had been influenced by amount of groundwater discharge and seawater flooding. The time-series data of EC, groundwater level, tide level, and precipitation were obtained and analyzed in terms of their cross-correlations. In the no rain period, tide level is the major factor of the changes, and tide level was positively correlated with the water level and negatively correlated with the EC. But rain events have intensively influenced on the water level and EC. EC at the upper zone of the inferred interface became lower by rain event, but those at the lower depth were contrast. It could mean that transition zone became thinner. Rainfall, the water level and tide level show negative correlation with EC at the upper depth, but poor correlation with EC at the lower depth.