An Analysis of the Groundwater Flow s Characteristics Following CLIMATE CHANGES

Gwangbok Choi,Seungseop Ahn,Kibum Park J-INSTITUTE 2021 International Journal of Human & Disaster Vol.6 No.4

Purpose: The purpose of this study is to estimate the groundwater volume available in the Gyeongju region and predict changes in the groundwater flow s characteristics based on the IPCC RCP climate scenario. Method: As for the method to carry out this study, the results of forecasting the weather conditions in the Gyeongju region based on the IPCC RCP climate change scenario were used. By using the predicted precipitation data, the groundwater volume available was analyzed by using the SWAT MODEL. To analyze the groundwater flow s characteristics, the future groundwater flow s characteristics were analyzed by using MODFLOW by using the observed water level related data. Results: When examining the content by scenario, and across all scenarios, it was analyzed that the M3 basin was the largest, followed by the M2 basin and the M1 basin, respectively. It was also analyzed to be inversely proportional to the size of the outflow hydrologic curve in the case of the M1 basin as the city area was greater than that of the M2 and M3 basins. It was analyzed that the scenario of RCP 2.6 had the lowest variation for the content by basin, and that RCP 4.5 had the largest variation by basin. In terms of the flow direction of the groundwater, the M3 basin flows from the mountainous terrain to the Deokdongcheon Stream along the Deokdong Lake, and the M2 basin flows from the south towards the direction of the Bomun Lake. The M1 basin was analyzed to be the Bukcheon basin and finally flows towards the west side of the Hyeongsan River, and the overall groundwater flow in the target basin was analyzed to flow along the river towards the west side of the Hyeongsan River. Conclusion: As a result of analyzing the groundwater volume available and flow’s characteristics in the Gyeongju region according to climate changes in this study, the amount of groundwater volume available in the future RCP scenario both increased in 2100 compared to the current precipitation. Yet, in the case of RCP 4.5, the duration of no precipitation decreased by 57.75% compared to 2020, and RCP 8.5 increased by 56.79%, and hence, it was analyzed that, as for the available volume in 2100, the RCP 4.5 scenario was calculated to be 6.93% higher than the present, and the RCP 8.5 scenario increased by 0.10% compared to the present. In 2100, when there was no precipitation for 40 or more days, it was analyzed that the groundwater level decreased for RCP 4.5 by 0.7 m on average, and as for RCP 8.5, it was analyzed to decrease by GL by 1.0 m, and hence, the water level’s decrease turned out to be very large for the RCP 8.5 scenario. As a result of the groundwater flow analysis, it was analyzed that it was advantageous for securing the groundwater because of the high groundwater volume available and the groundwater level in the RCP 4.5 scenario where the greenhouse gas reduction policy was significantly realized.

컨벌루션 기법을 이용한 제주도 표선유역 부정류 지하수 흐름 모델 개발

김승구 ( Seung Gu Kim ),구민호 ( Min Ho Koo ),정일문 ( Il Moon Chung ) 한국환경과학회 2015 한국환경과학회지 Vol.24 No.4

Groundwater level hydrographs from observation wells in Jeju island clearly illustrate distinctive features of recharge showing the time-delaying and dispersive process, mainly affected by the thickness and hydrogeologic properties of the unsaturated zone. Most groundwater flow models have limitations on delineating temporal variation of recharge, although it is a major component of the groundwater flow system. Recently, a convolution model was suggested as a mathematical technique to generate time series of recharge that incorporated the time-delaying and dispersive process. A groundwater flow model was developed to simulate transient groundwater level fluctuations in Pyoseon area of Jeju island. The model used the convolution technique to simulate temporal variations of groundwater levels. By making a series of trial-and-error adjustments, transient model calibration was conducted for various input parameters of both the groundwater flow model and the convolution model. The calibrated model could simulate water level fluctuations closely coinciding with measurements from 8 observation wells in the model area. Consequently, it is expected that, in transient groundwater flow models, the convolution technique can be effectively used to generate a time series of recharge.

터널모델링시 개념모델에 따른 지하수 유동 예측결과 비교연구

최미정 ( Mi Jung Choi ),이진용 ( Jin Yong Lee ),구민호 ( Min Ho Koo ),이강근 ( Kang Kun Lee ) 대한지질공학회 2004 지질공학 Vol.14 No.2

도로 및 철도 신설에 따른 터널 굴착으로 지하수가 유출될 경우 지하수 자원 고갈, 농업용수 및 생활용수 부족 및 지표수 유량의 변화 등이 예상된다. 이러한 터널 굴착에 따른 지하수계의 변화를 예측하기 위해 3차원 유한차분 모형인 MODFLOW가 가장 널리 이용되고 있는 추세이다. 지하수 유동 모델링 실무에서 개념모델의 설정은 가장 중요한 요소 중 하나이다. 개념모델을 너무 단순화하였을 경우 모델링 결과로부터 필요한 정보를 얻어낼 수 없는 상황이 발생할 수 있고, 혹은 너무 복잡하게 개념모델을 설정하였을 경우 필요한 현장 자료가 부족할 수 있으며, 수집이 되었더라도 모델을 구동하는데 과다하게 많은 시간과 자원이 소요될 수 있다. 본 연구에서는 터널 굴착에 관한 지하수 모델링을 수행할 경우 개념 모델 설정에 따른 모델링 결과를 비교하여 현실에 보다 적합하고 효율적인 개념모델 구성에 대해 고찰하였다. When the groundwater outflow occurs due to tunnel excavation during the road and railroad construction, depletion of groundwater resources, deficiency in the living and agricultural waters, and changes in the surface water flux are expected. The MODFLOW is a most commonly used and three dimensional finite difference model to predict changes in the groundwater system due to the tunnel construction. A conceptual model is one of the most important elements for the proper modeling results. Essential information will not be extracted from an oversimplified conceptual model while excess time and resources with much field data are required for the very complicated one. This study presented a comparison of the modeling results depending on some conceptual models and discussed construction of the efficient conceptual model for reasonable and realistic results in the tunnel modeling.

KURT 연구지역에서 지질모델을 이용한 수리지질모델의 구축

박경우(Kyung Woo Park),고낙열(Nak Yeol Ko),지성훈(Sung Hoon Ji) 대한자원환경지질학회 2018 자원환경지질 Vol.51 No.2

KAERI Underground Research Tunnel(이하 KURT)는 한국원자력연구원의 연구지역에 건설된 지하처분연구시설이다. 현재 KURT에서는 방사성폐기물의 심층 처분의 주요 핵심 요소인 공학적 방벽과 천연방벽에 대한 연구를 수행하고 있다. 본 연구에서는 심부영역의 부지특성평가기술을 구축하기 위해 수행된 KURT 연구지역의 부지특성조사를 종합하여, 부지 지질모델을 구축하고, 이로부터 3차원 수리지질모델을 도출하였다. 연구지역에서 수행된 지질조사와 시추공 조사 결과를 이용하여 분석한 결과, 수리지질학적 관점에서 중요한 풍화대, 상부 단열암반대, 하부 단열암반대와 심부 영역에 존재하는 결정론적 단열대를 정의하여 이들을 3차원으로 모형화 하였고, 구축된 지질모델과 현장수리시험 결과를 종합하여 지하수유동모델링 및 처분 안전성 평가에 주요한 입력 자료가 될 수리지질모델을 도출하였다. The KURT (KAERI Underground Research Tunnel) is a research tunnel which is located in KAERI (Korea Atomic Energy Research Institute) site. At KURT, researches on engineering and natural barrier system, which are the most important components for geological disposal system for high level radioactive waste, have been conducted. In this study, we synthesized the site characteristics obtained by various types of site investigation to introduce the geological model for KURT site, and induced the 3-D hydrogeological model for KURT site from the geological model. From the geological investigation at the surface and boreholes, four geological elements such as subsurface weathered zone, upper fractured rock, lower fractured rock and fracture zones were determined for the geological model. In addition, the geometries of these geological elements were also analyzed for the geological model to be three-dimensional. The results from 3-D geological model were used to construct the hydro-geological model for KURT site, which is one of the input data for groundwater flow modeling and safety assessment.

지하수 유동체계 해석을 위한 실무형 모델의 개발

최정우 ( Jeong Woo Choi ),최윤영 ( Yun Yeong Choi ),현길수 ( Kil Soo Hyun ) 한국수처리학회 2004 한국수처리학회지 Vol.12 No.3

N/A A practical model for analyzing groundwater flow system to be applicable in field site was developed by reconstructing the Koreanized 3-dimensional finite difference method(DFM) model(ver. 1.1.1 and 1.1.2) with 3-DFM model strengthened a graphic function for post process. The practical model developed in this study was applied to analyses ground flow system in Yangchon area, Sangju, Kyungbook. The WINFLOW model of 2-DFM was used to compare with the practical model. Based on the comparison of observed and computed values of groundwater level in well, the variation range of water level were 0.03m for 3-DFM at P4 well and 0.06m for WINFLOW at P well. The well showed the greatest variation range of water level were the well of P with 0.16m for 3-DFM and the well of P1 with 0.35m for WINFLOW. A relative error of observed and computed values ranged from 0.037 to 0.195% for 3-DFM and 0.073 to 0.419% for WINFLOW. This shows the 3-DFM model is more closer to observed value. Simultaneous pumping of P and P1 wells compared to single well increased the size of radius of influence and showed a little complicated aspect.

지하수 모델을 이용한 제주도 지하수 유동특성 및 수리전도도 분석

김민철,양성기,Kim, Min-Chul,Yang, Sung-Kee 한국환경과학회 2019 한국환경과학회지 Vol.28 No.12

We used numerical models to reliably analyze the groundwater flow and hydraulic conductivity on Jeju Island. To increase reliability, improvements were made to model application factors such as hydraulic watershed classification, groundwater recharge calculation by precipitation, hydraulic conduction calculation using the pilot point method, and expansion of the observed groundwater level. Analysis of groundwater flow showed that the model-calculated water level was similar to the observed value. However, the Seogwi and West Jeju watersheds showed large differences in groundwater level. These areas need to be analyzed by segmenting the distribution of the hydraulic conductivity. Analyzing the groundwater flow in a sub watershed showed that groundwater flow was similar to values from equipotential lines; therefore, the reliability of the analysis results could be improved. Estimation of hydraulic conductivity distribution according to the results of the groundwater flow simulation for all areas of Jeju Island showed hydraulic conductivity > 100 m/d in the coastal area and 1 - 45 m/d in the upstream area. Notably, hydraulic conductivity was 500 m/d or above in the lowlands of the eastern area, and it was relatively high in some northern and southern areas. Such characteristics were found to be related to distribution of the equipotential lines and type of groundwater occurrence.

산사태해석을 위한 GIS기반의 강우침투-지하수흐름 예측 기법 제안

김정환,정상섬,배덕효 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.7

This paper describes a GIS-based geohydrologic methodology, called YSGWF (YonSei GroundWater Flow) for predicting the rainfall infiltration-groundwater flow of slopes. This physical-based model was developed by the combination of modified Green-Ampt model that considers the unsaturated soil parameters and GIS-based raster model using Darcy’s law that reflects the groundwater flow. In the model, raster data are used to simulate the three dimensional inclination of bedrock surface as actual topographic data, and the groundwater flow is governed by the slope. Also, soil profile is ideally subdivided into three zones, i.e., the wetting band zone, partially saturated zone, and fully saturated zone. In the wetting band and partially saturated zones the vertical infiltration of water (rainfall) from surface into ground is modeled. When the infiltrated water recharges into the fully saturated zone, the horizontal flow of groundwater is introduced. A comparison between the numerical calculation and real landslide data shows a reasonable agreement, which indicate that the model can be used to simulate real rainfall infiltration-groundwater flow.

Comparison of Groundwater Modeling under Different Geological Models Constructed from High Resolution Borehole Data

( Mingyeong Kim ),( Jeryeong Kim ),( Minuk Ha ),( Minseo Bae ),( Juhee Kim ),( Ja-young Goo ),( Soonjae Lee ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

High resolution site characterization (HRSC) can support more effective remediation design and faster site cleanup. Recently, researches on HRSC techniques have conducted in Deokso area, Keonggi-do, Korea. In this research, we investigated the groundwater flow under different geological models constructed based on the detailed lithological and structural borehole log from the adjacent boreholes on the test bed. The conceptual hydrogeological models were constructed with homogeneous layer models as well as heterogeneous models. The homogeneous models were derived by interpolating observed contacts in borehole logs. Heterogeneous models were built by geostatistical simulation of lithology variables and material properties using T-PROGS. Over the generated hydrogeology model, the groundwater flow modeling was conducted using MODFLOW. The simulated groundwater flow field in homogeneous layer models were compared with the simulations in a heterogeneous model made with a T-PROGS tool. The simulation results showed that the groundwater flow varied greatly depending on configuration of the conceptual model as well as the resolution of geological survey data.

수리전도도의 불확실성을 고려한 학률론적 지하수 유동해석에 관한 연구

류동우(Dong-Woo Ryu),손봉기(Bong-Ki Son),송원경(Won-Kyoung Song),주광수(Kwang-Soo Joo) 한국암반공학회 2005 터널과지하공간 Vol.15 No.2

도심지 지하철 및 산악 터널의 굴착과 관련한 지하수 유동 해석 및 환경 영향 평가를 위해 3차원 유한차분 모형인 MODFLOW가 널리 이용되고 있는 추세이다. 수치해석 결과는 일반적으로 경계조건, 초기조건, 개념 모델 설정 및 수리 물성치 등에 의해 차이가 난다. 따라서 대상 해석 영역의 실제 상황을 반영한 지하수 모델링은 매우 중요하다. 일반적으로 지하수 유동 해석과 관련한 많은 경우, 경계 조건 설정보다는 수리 물성치의 결정에 어려움이 많으며, 이는 제한된 조사나 실험 결과로부터 전체 대상 영역의 매질을 결정하기 때문이다. 본 연구에서는 모의 담금질(SA : Simulated Annealing) 기법을 활용하여 지반 조사 자료, 특히 물리탐사 결과 이미지와 제한된 개소의 수리 전도도 자료를 병합하여 수리 매질들을 실현시켰다. 지구통계학적 등가 매질들을 대상으로 하여 수리 전도도의 불확실성을 고려한 지하수 유동 해석을 수행하였다. 지하수 환경 영향 평가 및 터널 내 유입 지하수 문제에 있어 수리 전도도의 불확실성을 고려함으로써 확률론적 접근이 가능하였다. MODFLOW, 3-D finite difference code, is widely used to model groundwater flow and has been used to assess the effect of excavations on the groundwater system due to construction of subways and mountain tunnels. The results of numerical analysis depend on boundary conditions, initial conditions, conceptual models and hydrogeological properties. Therefore, its accuracy can only be enhanced using more realistic and field oriented input parameters. In this study, SA(simulated annealing) was used to integrate hydraulic conductivities from a few of injection tests with geophysical reference images. The realizations of hydraulic conductivity random field are obtained and then groundwater flows in each geostatisticallv equivalent media are analyzed with a numerical simulation. This approach can give probabilistic results of groundwater flow modeling considering the uncertainty of hydrogeological medium. In other words, this approach makes it possible to quantify the propagation of uncertainty of hydraulic conductivities into groundwater flow.

Simulation on the cyclic operation of an open borehole thermal energy storage system under regional groundwater flow

이근상 한국지질과학협의회 2010 Geosciences Journal Vol.14 No.2

Coupled hydrogeological-thermal simulation is performed to analyze the effect of the configuration of boreholes and operation schedule on the performance of the borehole thermal energy storage (BTES) system. This paper presents numerical investigations and thermohydraulic evaluation on the cyclic flow regime operation of open borehole thermal energy storage system under the effects of regional groundwater flow. A three-dimensional numerical model for groundwater flow and heat transport in the ground is used to determine the annual variation of recovery temperature from the thermal energy storage. The model includes the effects of convective and conductive heat transfer, heat loss to the adjacent confining strata, and hydraulic anisotropy. The operation scenario consists of cyclic injection and recovery after holding interval and four periods per year to simulate the seasonal temperature conditions. For different parameters of the system, performances were compared in terms of the variation of extraction temperature. The calculated water temperature at the producing pipe remains relatively constant within a certain range throughout the simulation period. Heat loss, injection/production rate, aquifer thickness, and permeability ratio used in the model are shown to impact the predicted temperature profiles at each stage and the recovery water temperature. The influence of pressure gradient, which determines the direction and velocity of regional groundwater flow, is substantial for all cases considered.