Stratigraphic analysis of the drilling core in Woljong-ri coastal area, Jeju Island

Koh, Chang-Seong; Hoon, Yoon Seok; Hong, Jeong-Gyun; Jeong, Jongok; Kimjinju,

doi:10.14770/jgsk.2019.55.1.1

Cited by 9 publications

(2 citation statements)

References 28 publications

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“…Jeju Island was formed by repeated volcanic eruptions, therefore, its geology has been controlled by lava features generally divided into pahoehoe and aa lava [43][44][45]. The basaltic rocks contain interflow structures (notably clinker layers) that are permeable with a high porosity [46].…”

Section: Methodsmentioning

confidence: 99%

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

Shin

Hwang

2020

Water

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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.

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Section: Methodsmentioning

confidence: 99%

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

Shin

Hwang

2020

Water

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“…The hyaloclastite and lower basalt extend from 50 to 95 m below sea level, and the sedimentary formation extends from 90 to 132 m below sea level. Koh et al (2019) analyzed the MW 2-1 drilling core and simplified its lithostratigraphy. They defined the basalt, hyaloclastite, and the following lower basalt as a hydrologically connected volcanic rock.…”

Section: Site Descriptionmentioning

confidence: 99%

Vulnerability assessment considering impact of future groundwater exploitation on coastal groundwater resources in northeastern Jeju Island, South Korea

et al. 2020

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Jeju Island is the largest island in South Korea. Recently, extensive groundwater abstraction has been reported from the shallow aquifer in the northeast region of the island. This study simulated the freshwater resources of the aquifer to estimate the sustainability of groundwater use on Jeju Island in terms of its vulnerability to seawater intrusion. Three-dimensional finite-difference numerical groundwater models were simulated using the MODFLOW-family code SEAWAT. Precise and recent groundwater level and multi-depth salinity data obtained from the study site were used for model calibration; the simulated results showed good agreement with the observed data. SEAWAT was used to delineate the current seawater-freshwater interface to quantitatively estimate the coastal fresh groundwater resources. Future stress scenarios were also simulated in response to increased pumping and various changes in the recharge. The results showed that current groundwater use in the coastal aquifer did not induce seawater intrusion in the coastal aquifer, but seawater intrusion will occur if the dry season continues for the next ten years. The vulnerability assessment based on the predicted groundwater levels and ion concentrations using numerical simulations suggests future vulnerability in the aquifer; therefore, continuous assessment and visualization of the aquifer sustainability is vital. Future projections by the integrated SEAWAT simulation and GALDIT assessment showed that an increase in groundwater pumping may escalate the vulnerability status of coastal groundwater resources from moderate to high in some areas of the study site, by inducing lateral seawater intrusion in deeper areas of the unconfined aquifer.

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Reexamination of the magma plumbing system of the Suwolbong tuff ring, Jeju Island, Korea, based on a refined componentry analysis

Go,

Ahn,

Ahn

et al. 2024

Geosci J

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Stratigraphic analysis of the drilling core in Woljong-ri coastal area, Jeju Island

Cited by 9 publications

References 28 publications

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

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

Vulnerability assessment considering impact of future groundwater exploitation on coastal groundwater resources in northeastern Jeju Island, South Korea

Reexamination of the magma plumbing system of the Suwolbong tuff ring, Jeju Island, Korea, based on a refined componentry analysis

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