제주도 서부 해안지역의 수문지질과 지하수 부존특성

Abstract

The purpose of this study is to grasp the geohydrological features of western coast aquifer surveyed through analysis of geological logging, geophygical logging, aquifer test and chemical water quality by aquifer with the object of 13 seawater intrusion monitoring wells at the western parts set by Jeju special governed Island. The geological features at the study area are divided into 5 units of underground geological like lava sequence that ranges throughout the top of Seoguipo Formation with carious thickness, Seoguipo Formation, U Formation, sedimentary layer that contained between lava sequence, and lava flows that contained between Seoguipo Formation. As a result of analysis of aquifer test, it is concluded that most range of aquifer in study area develops at volcanic rocks of jointed and/or hyaloclastite breccias, the aquifer are found as fallow in Seoguipo Formation and gravel layer between lava sequence, and gravel layer in Seoguipo Formation or unconsolidated sand layer. According to the result of classification of chemical water quality and groundwater occurrence type, one is basal groundwater regions(HL1, SD, HM),and the good water quality of parabasal groundwater regions(SM1, IG) the other one is the poor quality of water regions(the rest of other monitoring wells). there is high content of NO3-N in the upper part of the poor quality of water regions As a result of geophygical logging, it is set against drilled core collected in the process of well dilling underground. As a analysis of natural gamma, there represent high value in sedimentary layer of lava sequence and section which has lots of clay in Seoguipo Formation. Conductivity of Shindo and Hamo has increased with as conductivity getting deeper and it's reached to approximately 30,000～40,000, which makes sure that there is salinewater below freshwater.