• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.4
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• pp.327-336
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• 1992

In order to establish one of the forecasting model for the fishing conditions of squid angling fisheries in the Eastern Korea Sea, the catch data for the years of 1955~1991 and the water temperature data for the years of 1979~1990 were analysed, and then some parameters, that is, the water temperature normal year anomaly in the spawning and the rapidly growing season, the adult resource amount and etc were examined statistically correlation with the catch fluctuation of the main fishing seasons. From the result, authors suggested a formula as a forecasting model, Y=25785+1099X sub(1)+1074X sub(2)+6.033X sub(3)+3.95X sub(4)+1.330X sub(5)(M/T)(R super(2)=0.867, P<0.01) in the case that Y is the yearly catch, X sub(1) and X sub(2) are the water temperature normal year anomalies in October and December of the previous year and that in February and April, and X sub(3), X sub(4) and X sub(5) are the catches in October, in September, in November of previous year respectively. Because these parameters could be checked in earlier time of a half year before the main fishing season, this model was assumed to be very useful for the prediction of fishing conditions of squid angling fisheries.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.6
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• pp.450-458
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• 1991

The thermal structures and their spatio-temporal fluctuations in the upper 200m layer off the southeast coast of Korea are studied using the bimonthly temperature data for 17years(1967-1983) at 37 stations. We analyzed the fluctuations of the temperatures in the surface(0-100m) and in the subsurface(100-200m) layers. The fluctuations of temperatures in the surface water are dominated by the annual variation, whereas the subsurface layer temperatures contain considerable non-seasonal fluctuations. The distributions of water temperature anomalies in the subsurface layer are closely related with those in the surface layer. The predominant periods of temperature fluctuations in the subsurface layer, other than the annual variation, are 14 and 70 months. The period of 14 months coincides with that of the pole tide or Chandler wobble. The cluster analysis shows that our study area can be divided into the cold, the frontal and the warm regions.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.305-305
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• 2022

A better approach for assessing meteorological drought occurrences is increasingly important in mitigating and adapting to the impacts of climate change, as well as strategies for developing early warning systems. The present study defines meteorological droughts as a period with an abnormal precipitation deficit based on monthly precipitation data of 18 gauging stations for the Han River watershed in the past (1974-2015). This study utilizes a Bayesian parameter estimation approach to analyze the effects of climate change on future drought (2025-2065) in the Han River Basin using the Coupled Model Intercomparison Project Phase 6 (CMIP6) with four bias-corrected general circulation models (GCMs) under the Shared Socioeconomic Pathway (SSP)2-4.5 scenario. Given that drought is defined by several dependent variables, the evaluation of this phenomenon should be based on multivariate analysis. Two main characteristics of drought (severity and duration) were extracted from precipitation anomalies in the past and near-future periods using the copula function. Three parameters of the Archimedean family copulas, Frank, Clayton, and Gumbel copula, were selected to fit with drought severity and duration. The results reveal that the lower parts and middle of the Han River basin have faced severe drought conditions in the near future. Also, the bivariate analysis using copula showed that, according to both indicators, the study area would experience droughts with greater severity and duration in the future as compared with the historical period.

• Journal of Korea Water Resources Association
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• v.47 no.4
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• pp.385-396
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• 2014

Lately, more frequent typhoons cause extensive flood and wind damage throughout the summer season. In this respect, this study aims to develop a probabilistic clustering model that uses both typhoon genesis location and trajectories. The proposed model was applied to the 197 typhoon events that made landfall in the Korean peninsula from 1951 to 2012. We evaluate the performance of the proposed clustering model through a simulation study based on synthetic typhoon trajectories. The seven distinguished clusters for typhoons affecting Korean peninsula were identified. It was found that most of typhoon genesis originated from a remote position ($10^{\circ}{\sim}20^{\circ}N$, $120^{\circ}{\sim}150^{\circ}E$) near the Equator. Cluster, type B can be regarded as a major track due to the fact that its frequency is approximately about 25.4% out of 197 events and its direct association with strong positive rainfall anomalies.

• Journal of Korea Water Resources Association
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• v.57 no.10
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• pp.757-767
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• 2024

In the Hankyung-Daejeong watersheds of western Jeju Island, several groundwater wells showed abnormal measurements of high electrical conductivity (EC) and pH. To identify the causes of this abnormal water quality, we conducted borehole imaging, vertical EC logging, groundwater quality analysis, and SEM-EDS analysis of white suspended matter in the well. Most of the wells showing abnormal water quality had well-grouting below the water table, with borehole EC values ranging from 300 to 10,000 μS/cm. The wells exhibited higher ion concentrations compared to nearby wells and had a high pH range of 8.2 to 12.7, indicating a slightly to strong alkalinity. The primary components of the white-colored suspended matter were identified as oxygen and magnesium. These findings suggest that the abnormal water quality of the study wells is caused by the cement mortar used for grouting during well construction rather than by nitrate contamination or seawater intrusion. To prevent the influence of well-grouting on water quality during groundwater well development, an establishment of standards for groundwater development and utilization facilities is needed.

• Economic and Environmental Geology
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• v.46 no.2
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• pp.105-121
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• 2013

This study introduces integrated approach on detection of a leakage in a sea wall based on remote sensing, electric resistivity survey, electromagnetic survey, and borehole survey for the Seosan A-Region sea wall. The satellite temperature distribution from Landsat ETM+ data identifies water leakage distribution and period by analyzing temperature mixing patterns between sea water and fresh water. Electric resistivity survey provides both horizontal and vertical anomaly distributions over the sea wall showing below average electric resistivity. Electromagnetic survey(electrical conductivity survey) reveals the potential possible leakage areas with minimal background impact by comparing electrical conductivity values between high and low tides. Borehole image processing system confirmed the locations of anomalies identified from the other survey methods and distributions of vertical fracture zones. The integrated approach identified 41.7% of the sea wall being the most probable area vulnerable to water leakage and effectively approximated both horizontal and vertical distribution of water leakage. The integrated analysis of remote sensing, electric resistivity survey, electromagnetic survey and borehole survey is considered to be an optimal method in identifying water leakage distribution, period, and extent of fractures knowledged from the boreholes.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.640-641
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• 2003

Abnormal oceanic conditions associated with the passage of typhoons are examined using hydrographic and satellite data 1990-2002. During the passage period of typhoons in the Korean waters, an abrupt decrease of sea surface temperature(SST) in range of 5 to 8 $^{\circ}$ was observed. The areas of SST decrease were an order of 100-200km, and the low SST lasted about 15-25 days after passage of typhoon. After passage of typhoon, the water temperatures in the surface mixed layer of 30m show negative anomalies for quite a long period. In addition, stratification parameters were substantially decreased and chlorophyll a density was rapidly increased.

• Korean Journal of Ecology and Environment
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• v.40 no.4
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• pp.546-552
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• 2007

The objectives of this study were to analyze fish compositions, based on trophic guilds and tolerance guilds and determine community characteristics structure at five sampling sites of Yeongsan Lake during July 2006-May 2007. Total number of species sampled was 30 species and the number was 1350. Cyprinidae (77%) and Centrarchidae (15.7%) dominated the community and then followed by Cobitidae(2.7%), Gobiidae(2.4%), Mugilidae (0.5%), and others (0.1%). The relative abundance of tolerant and omnivore species at all sites was 63% and 77% of the total, respectively, suggesting an ecological degradations in the Lake. Exotics species such as large mouth bass (Micropterus salmoides), which is a top-carnivore in the water distributed at all sampling sites, implying that ecological disturbance was severe based on previous reference of US EPA (1991). Also, we found external anomalies such as external deformities, bleeding and tumors and not found migratory fish. Analysis of fish community structure showed that species diversity index and richness index was the highest in Site 1 and the dominance index was the highest in Site 2. In this study, high proportions of tolerant species and omnivore species, widespread exotic species, and frequent observations of abnormal fish. Such problems may be directly or indirectly associated with high nutrient enrichments and the reduced flow velocity by the dam construction. The ecosystem restoration by dam removal or removal of exotic top-carnivore fish may be one of the best strategies for better lak management.

• Toxicological Research
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• v.11 no.1
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• pp.91-101
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• 1995

A perinatal and postnatal study of KTC-1, a new semisyntheitic rifamycin antituberculous drug, was conducted in Sprague-Dawley rats. Dosages of KTC-1 0, 12, 27.6, and 63.5 mg/kg/day were administered to dams orally by gavage from day 17 of gestation to day 21 of lactation. All pregnant rats were allowed to deliver naturally for postnatal examination of their offspring. At 63.5 mg/kg/day, weakness, dark-red discharge around eyes, a loss in body weight, and a decrease in food and water consumption were observed in dams. An increase in the weight of adrenal gland and spleen, and a decrease in the weight of kidney and heart were also found. An increase in neonatal deaths during the lactation period, a loss in body weight, a delay in physical development, a decrease in traction ability, an increase in the number of errors and the time required for the multiple T-maze trial were found in F1 offspring. In addition, an increase in the incidence of visceral variations and retarded ossification were observed in F1 4 day old rats. An increase in the incience of skeletal anomalies was seen in F2 fetuses. There were no sings of maternal toxicity or embryotoxicity at 12 and 27.6 mg/kg/day. From the results mentioned above, it can be concluded that the no-effect dose levels(NOELs)for dams, F1 offspring, and F2 fetuses are 27.6 mg/kg/day.