제주도 동부지역 염지하수 관정의 수리지질학적 특성

Abstract

For the saline groundwater wells of Namweon, Pyoseon, Seongsan, Gujwa and Jocheon basins in the eastern coastal area of Jeju Island, their hydrogeological characteristics were investigated, using the characteristics of groundwater reserve by the data of vertical logging of electrical conductivity and by those of underground geology, together with the results of hydraulic parameters calculated by the tidal response technique. The wells in this study area showed that low saline groundwater by mixing of the fresh groundwater inflowed from inland with seawater was distributed in the upper part and saline groundwater without mixing of fresh groundwater and seawater was distributed in the lower part. The saline groundwater can be reserved in the clinker layer and crushing joint derived from the compact Aa lava, the pillow lava layer and the hyaloclastite breccia layer founded in the bottom of wells. The hydraulic diffusivity (T/S) values calculated by applying the groundwater level data for these wells and tidal level data in the eastern area of Jeju Island, were in the range of 2.33×107 m2d-1∼4.56×107 m2d-1. The transmissivity (T) values were in the range of 232,558∼13,667,426 m2d-1 and 233∼45,600 m2d-1 with regard to unconfined one and an confined one, respectively, and the latter values are similar to those (731∼44,100 m2d-1) reported in this area earlier. In addition, it was considered that the aquifer type in this study area was similar to a leaky aquifer (showing a severe leaky phenomenon) or a semi-confined one rather than a complete confined one, based on the geological characteristics such as vertical joint and crushing plane.