• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.83-83
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• 2015

최근 수자원 이용량의 증가 및 수자원 공급의 부족에 따라 대안으로 제시되고 있는 지하수 이용은 매년 크게 증가하고 있다. 내륙 지역의 지하수 개발 시와 비교할 때 해안 지역의 지하수 개발에는 해수침투 현상에 대하여 추가적 고려가 필요하다. 알려진 바와 같이 해안 지역의 과잉 양수와 해수면 상승 으로 해수침투가 더욱 깊이 침투하고 있는 실정이다. 이에 대해 정략적인 해수 침투길이 산정과 더불어 해수침투를 허용가능한 범위 내로 제한 시키는 지하수 개발이 필요하다. 해수침투 저감 공법에는 저투수차수벽 설치, 담수주입공법, 해수양수공법으로 크게 3가지로 구분할 수 있다. 저투수차수벽의 해수침투 저감 효율은 크지만 비용이 비싸다는 단점으로 본 연구에서 제외시켰다. 담수주입공법은 대수층에 담수를 주입하여 해수침투를 저감시키는 공법으로 인근에 양질의 수원을 필요로 하는 단점이 있다. 해수양수는 해안가에 양수정을 설치하여 해수침투를 저감시키지만 양수정에서의 담수가 혼합되어 담수낭비가 생기는 단점이 있다. 본 연구에서는 해안지하수의 해수침투를 저감시키기 위한 방법중 담수주입과 해수양수공법의 효율을 검증하고 각각 공법의 장단점을 비교하였다. 지하수 경계면 모델을 이용하여 각각의 수리수문 변수들이 미치는 영향과 해수침투 정도를 사례별로 연구하였다. 담수주입공법의 경우 담수주입량 많을수록 해수침투가 저감되는 경향이 있지만 최적의 담수주입량을 찾는데 목적이 있다. 해수양수공법에는 해수양수량이 증가하고 해수양수정의 위치가 해안선에 접할수록 해수침투 저감 효과가 있었다. 담수주입공법과 해수양수공법을 해수침투 저감을 위해 해안가에 적용할 경우 해당 지역의 특성을 면밀히 분석하여 적용해야 효과를 볼 수 있다.

• Journal of Korea Water Resources Association
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• v.47 no.11
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• pp.1087-1094
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• 2014

Saltwater pumping method can be used to mitigate saltwater intrusion in coastal aquifers. However, the saltwater pumping well may discharge large freshwater along with saltwater, thereby wasting precious resources. A double negative barrier was proposed: an inland well to capture freshwater and a saltwater well near the coastline to pump saltwater. A previous study anaylzed effects of double negative barriers in dispersion-dominated coastal aquifers and determined the critical pumping rate at the saltwater well which minimized the saltwater ratio at the freshwater well. However, the study resulted in 1~15% of saltwater ratios, which were too high, for example, for drinking water standards. This study analyzed cases that were considered in the previous study, but for advection-dominated cases, and found that freshwater with sufficiently low saltwater ratios could be developed at the freshwater well. In addition, for optimal groundwater management of a watershed not only the minimum saltwater ratio at the freshwater well but also the least freshwater wasted at the saltwater well must be pursued.

• The Journal of Engineering Geology
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• v.13 no.1
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• pp.17-27
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• 2003

In this study, a phenomenon of saltwater intrusion was monitored under various conditions regarding recharge and pumping rate using time domain reflectometry for a laboratory scale unconfined aquifer to verify the basic theory behind seawater intrusion and to investigate movement of salt-freshwater interface in accordance with the ratio of pumping and recharge rate. Results showed that a thick mixing zone was formed at the boundary instead of a sharp salt-freshwater interface that was assumed by Ghyben and Herzberg who derived an equation relating the water table depth $(H_f)$ to the depth to the interface $(H_s)$. Therefore our experimental results did not agree with the calculated values obtained from the Ghyben and Herzberg equation. Position of interface which was adopted as 0.5 g/L isochlor moved rapidly as the Pumping rate $(Q_p)$ increased for a given recharge rate $(Q_r)$. In addition, interface movement was found to be about 7 times the ratio of $Q_p/Q_r$ in our experimental condition. This indicates that Pumping rate becomes an important factor controlling the seawater intrusion in coastal aquifer.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.2001-2006
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• 2010

본 연구에서는 수리모형실험을 통해 해안지역 대수층에서 해수침투가 일어나지 않는 지하수의 최적 양수량을 산정하였다. 해안 대수층 및 양수정을 구현하기 위해 가로 140 cm, 세로 70 cm, 두께 10 cm 의 직사각형 Sandtank 모형과 5 mm 원형관을 이용하여 수행하였다. 해수의 염도, 해안가의 지표경사 등을 기준으로 설정하였으며, 다공질 매체의 입자크기에 따른 수리전도도 2가지를 경계조건으로 하여 각각의 양수정 위치에 따라 최대 담수량을 모의하였으며, 이 때, 하나의 과잉 담수량에 따른 최적 염수량을 산정하여 염수침투 제어 효과를 검증하였다. 다공질매체의 수리전도도가 높을수록 최대 담수량이 증가되며 이에 따라 염수 침투 제어를 위한 최적염수량이 증가하였다. 또한 양수정의 위치가 염수조에 가까울수록 최대담수량 및 최적염수량이 감소되었다. 이러한 모의를 통하여 설정된 각각의 양수정 위치에서 최적의 염수량으로 염수침투를 제어함으로써 지속시간 이용가능한 최대담수량을 나타내었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.527-535
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• 2018

Agricultural activities of western Jeju island has suffered from saltwater intrusion seasonally. Objectives of this study are to prove the occurrence of saltwater intrusion in the coastal aquifer and to consider a management plan using MODFLOW-family code SEAWAT model. Model results show that the saltwater-freshwater interface intrudes inland only a few meters and that upconing phenomenon is rather the cause of the severe disaster of the agricultural water contamination. This study selected Gosan area as a representative site to estimate optimal groundwater development regulation against upconing by seasonal pumping for agriculture. The suggested optimal groundwater development estimation method considers the groundwater levels of representative monitoring wells for regulatory alarms.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.603-612
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• 2006

The study with laboratory sandbox model has been carried out to address potential use of reclaimed water, as a way for artificially recharging the coastal aquifer, to effectively prevent from seawater intrusion. To do this, we assessed hydraulic and geochemical properties depending upon various extraction and recharging conditions. While solely being recharged, the intrusion could be significantly retarded than those of recharge and extraction implied together. At 0.5 to 2 for the ratio of the extraction over the recharge rate, the fresh water was exploited from the tank, where the void regime was simultaneously saturated with the recharged water. In the meantime, the saline water zone was diluted and back-tracked by the recharged water due to forming a hydraulic geochemical barrier around the injection well. However, if the ratio was being increased to greater than 4, saltwater more deeply intruded to the freshwater zone because the artificial recharge was not sufficiently supplied to timely back-fill the void space. When the aquifer water was intermittently extracted at the ratio of $0.5{\sim}2$ over the recharge rate, the value of S.M.I. decreased, but increasing it to more than 4 unlikely escalated the value of S.M.I as much as $3{\sim}47%$ indicating that the salt water intruded. It finally revealed that the proper ratio of extraction/recharge or intermittent extraction would efficiently retracted seawater intrusion while the freshwater sources could be conservatively utilized.

• Journal of Korea Water Resources Association
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• v.42 no.5
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• pp.415-424
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• 2009

Artificial injection of surplus surface water during wet seasons and recovery is one of possible solutions for conjunctive uses of surface water and groundwater. The methodology is especially attractive for regions of monsoon type weather. In this work a simulation-optimization model is developed to identify an optimal injection system to sustain an over-exploiting freshwater pumping well. The injection well is to be operated during wet seasons only while the pumping well is to be operated throughout an entire year. The objective function is the minimization of injected volume of freshwater. Saltwater intrusion and dry wells are considered as constraints. An example application is made on a small hypothetical island with poor hydrogeologic conditions. The optimization model is successful in determining optimal injection locations and rates for various cases.

• Tunnel and Underground Space
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• v.14 no.3
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• pp.229-240
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• 2004

Coastal aquifers may serve as major sources fur freshwater. In many coastal aquifers, intrusion of seawater has become one of the major constraints imposed on groundwater utilization. The management of groundwater in coastal acquifers means making decision as to the pumping rate and the spatial distribution of wells. Several numerical techniques for flow and solute transport simulation can provide the means to achieve this goal. As a basic study to predict the intrusion of seawater in coastal phreatic aquifers, the coupled flow and solute transport analysis was conducted by use of the 3-D finite element code, SWICHA. In order to understand how the location and the shape of freshwater-seawater transition zone were affected by the boundary conditions and hydrogeologic variables, parametric study was carried out.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1895-1899
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• 2006

Seawater intrusion phenomenons of coastal area happen by natural or artificial factor. For example, density difference of seawater and fresh water, surface of the water change by tidal current, pumping, aggregate picking from mouth of a river, large scale reclamation in water area business etc. This research analyzed effect that groundwater TDS changed by pumping.As a result, it was expose that TDS density increases by sudden inflow of seawater when do pumping up more than $200m^3/day$. Finally, We are expected to prevent calamity by seawater intrusion in coastal area through this study and propose optimum pumping amount to use groundwater safety.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1982-1985
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• 2010

해수침투는 대수층의 염분 농도를 증가시켜 지하수 염분화에 의한 용수의 부족 등을 야기시키며 다른 지하수 오염과 마찬가지로 회복에 대한 막대한 비용과 시간이 소모되어 피해지역에 대한 정확한 현황파악이 어려워 피해방지대책의 수립이 필요한 실정이다. 따라서 본 연구에서는 흐름과 이송을 모의할 수 있는 GMS-FEMWATER 모델을 이용하여 대상지역의 지층구조를 구분하고 실제 대상지역의 지층과 동일하게 모델링하여 해안지역의 해수침투에 대한 특성을 규명하였다. 분석결과 양수기간이 길어 질수록 지하수두강하 폭이 양수기간 30일, 60일, 90일 및 180일 경과 시 초기 수위에서 점차 4.25m (1.36%), 3.5m (1.13%), 2.96m (0.97%), 1.97m (0.65%)으로 감소하는 것을 알 수 있었다. 또한 양수량이 많은 관정일수록 해수 침투가 큰 것을 알 수 있다. 양수기간 30일 0.59mg/l, 채수 60일 1.65mg/l, 채수 90일 3.14mg/l, 180일 5.55mg/l으로 분석되었다. 이결과로 볼 때 양수기간 초기에서 기간이 지날 수록 해수침투가 큰영향을 주는 것을 알 수 있었다.