A Borehole-Based Approach for Seawater Intrusion in Heterogeneous Coastal Aquifers, Eastern Part of Jeju Island, Korea

Abstract

Understanding the basaltic aquifer system and seawater intrusion on the volcanic island of Jeju, Korea, has received significant attention over the years, and various methodologies have been suggested in the contributions. Nevertheless, it is still difficult to effectively characterize groundwater systems due to the long period of volcanic activity and the lithological variability of basalt. In this study, geophysical well logging in seawater intrusion monitoring boreholes detected a sudden decrease of electrical conductivity within the saltwater zone in the eastern part of Jeju Island. This anomalous condition cannot be explained by the Ghyben-Herzberg model, which has historically been considered as the basic groundwater model of Jeju Island. This paper focuses on fine-scale temporal and spatial variability of groundwater flow using electrical conductivity and temperature logs and borehole temperature monitoring by a thermal line sensor. On the basis of the results, we evaluate an alternative model to replace the traditional conceptual model in the eastern part of Jeju Island. It is revealed that the area consists of heterogeneous aquifer systems, and the behavior of freshwater and saltwater is understood by temperature monitoring over the entire depth of boreholes. Coastal aquifers flow through two or more independent channels with weak vertical connections. In addition, seawater intrusion does not occur continuously in the vertical direction from the bottom depth, but instead occurs through these multilayered aquifers. In particular, the multilayered aquifers that are responsible for flow pathway, as well as the freshwater–saltwater interface form mainly at lithological boundaries. Our preliminary conceptual model is expected to be improved and revised by various measurements of hydrodynamic parameters such as flowmeter or packer test.

Analysis of Hydrothermal Systems Beneath Tayukeng through Long-Term Geochemical Signals of Hydrothermal Fluids in Tatun Volcano Group, Taiwan

“…In many volcanic areas, temporal variations in Cl − concentration in thermal water can serve as an effective indicator of magmatic fluid migration [ 2 , 3 , 7 ]. In some cases, seawater could influence the compositions of spring water [ 42 ]. Some of the springs near the sea in the northeast of TVG are affected by seawater [ 43 ].…”

Hydrochemical-geophysical study of saline paleo-water contamination in alluvial aquifers

“…The systematic use of probes equipped with sensors for temperature (Polemio et al 2009;Vandenbohede et al 2014) and electrical conductivity measurements (Cotecchia et al 1999;Smart and Worthington 2003;Di Sipio et al 2006;Polemio et al 2009;Tal et al 2019;Shin and Hwang 2020) allows for the collection of significant and rapid data, albeit qualitative, on the chemical-physical characteristics of the groundwater.…”

Geochemical Approach for Seawater Intrusion Assessment in the Area around Yogyakarta International Airport, Indonesia

“…The groundwater quality is influenced by these cations and anions (Zghibi et al, 2012;Fathi Ubeid and Al-Agha, 2020). In addition, Electrical Conductivity (EC) value in the groundwater analysis is a physical parameter that important to determine seawater intrusion (Shin and Hwang 2020). Therefore, it is necessary and urgent to understand how geochemical environments regulate groundwater evolution and how hydrogeological conditions constrain circulation (Zhang et al, 2015).…”