Understanding of aquifer characteristics and evaluating the responses of aquifer type to earthquakes from the National Groundwater Monitoring Station

Long-term observation data from monitoring well have been used to evaluate groundwater system and provide parameters for managing groundwater resources (quantity and quality). However, when the classification information for aquifer system is clear, correct data interpretation is possible. Therefore, we conducted the characterization of aquifer system and analyzed the groundwater level fluctuation and water quality property using the 159 pairs monitoring data from the National Groundwater Monitoring Network (NGMN) in Korea. In addition, the responses of groundwater level change to temporal events such as earthquakes were compared and analyzed using the selected six monitoring well pairs neighboring the Gyeongju earthquake in 2016. When the precipitation was recharged, the time lag in the confined aquifer was greater than the deep bedrock aquifer (according to the depth). In most cases the water quality types of the well pairs were consistent, however, in some monitoring wells with different water quality showed different aquifer characteristics. When the Gyeongju earthquake was occurred, the significant changes were analyzed in the two monitoring wells among the six well pairs near the epicenter. The significant noises in the groundwater level were not observed in the shallow unconfined aquifers, but well observed in the deep confined aquifers. Therefore, the aquifer type should be clearly analyzed and for managing water resources or detecting natural hazard (e.g. earthquake) using groundwater observation, monitoring data should be acquired/utilized according to the aquifer type.