• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.3
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• pp.94-102
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• 2003

A hydrologic and water quality monitoring network were established in the Balkan-reservoir watershed, which has 29.79 $km^2$ in size, to analyze the characteristics of pollutant loading from an agricultural small watershed. Soil type, land use, hydrologic soil group, population and livestock were also surveyed to make clear the pollutant sources and to calculate the pollutant loadings by the unit loading factor method which was proposed by the Ministry of Environment. From the 5-year hydrologic monitoring results, sub-watersheds located in the upstream of the reservoirs showed higher average runoff ratio. The calculated daily pollutant loadings by the unit loading factor method from HP#2 sub-watershed in the downstream of Balkan reservoir, were much greater than observed.

• Korean Journal of Environmental Biology
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• v.32 no.4
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• pp.319-326
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• 2014

Fish community was investigated in eutrophic Jeondae agricultural reservoir from April to November 2012. The food web structure of major fish species of Jeondae reservoir showed that due to serious organic pollution, the hyper-eutrophic condition with high chemical oxygen demand (COD), chlorophyll-a (Chl-a), total nitrogen (TN) and total phosphorus (TP), as estimated by stable isotope analysis. Total of 679 individuals were collected from the reservoir, and 9 species were identified. Interestingly, Lepomis macrochirus and Hemiculter eigenmanni known as less sensitive to pollution and water quality deterioration, dominated the reservoir, and their relative abundances were 38% and 27%, respectively. Further, the analysis of the stomach contents revealed that main food source of dominant L. macrochirus was high amount of zooplankton, which includes copepoda and cladocera, while Cyprinidae species mainly consumed organic particles with zooplankton preys. Stable isotope analysis also suggested that L. macrochirus, Carassiusauratus, Pseudorasboraparva, and H. eigenmanni are major zooplantivorous group in the Jeondae Reservoir.

• Korean Journal of Environment and Ecology
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• v.33 no.4
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• pp.402-407
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• 2019

In this study, we investigated the habitat characteristics of a reservoir in Gyeongju City, Gyeongbuk, in which a large group of Mauremys reevesii (endangered species Class II and natural monument No. 453 in Korea) was discovered. We examined the biotic and abiotic factors that directly and indirectly threaten the survival of M. reevesii within the habitat. The reservoir where M. reevesii was discovered was built for agriculture and surrounded by submerged trees, dam, forests, reeds, and farmland (paddy field). All of the M. reevesii were found only in the submerged trees on the north side of the reservoir. We found 28 M. reevesii (8 juveniles) and 21 M. reevesii (16 juveniles) from field surveys on May 10th and August 9th, 2018, respectively. A number of red-eared sliders (Trachemys scripta elegans) and American bullfrogs (Rana catesbeiana), which threaten the survival of M. reevesii, were also found in and around the reservoir. Moreover, there were signs of excavation of cultural asset, chemical fertilizer, and household garbage, all of which are considered to be major threats to the survival of M. reevesii, all over the reservoir. Newborn turtles in this year were not observed. However, we estimated that natural breeding had sufficiently occurred since we observed many young turtles in the reservoir. Furthermore, the presence of young T. s. elegans individuals can be a persistent problem for M. reevesii as they are competing species. In conclusion, in-situ conservation method should be considered for protecting the endangered turtle and their habitat.

• Journal of Life Science
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• v.19 no.12
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• pp.1758-1763
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• 2009

Biological assessments of benthic macroinvertebrates community structure were carried out in ten reservoir inflow and outflow areas of the Nakdong river system from April 2008 to August 2008. The collected benthic macroinvertebrates from the surveyed sites were 9,427.6 inds./$m^2$, 42 species belonging to 29 families and 16 orders. A dominant species was Chironomus sp. and a subdominant species was Ecdyonurus levis. In the all sites, Ephemeroptera had the most number of species (17.81%) and Diptera had the most number of individuals (64.00%). Dominance, species diversity, species richness, and species evenness indexes were 0.68, 2.42, 2.96 and 0.54, respectively. The numbers of benthic macroinvertebrates species in each surveyed site were from 21 (site 9 Jilnal wetland) to 51 (site 2 Yeongcheon reservoir). As a result of an analysis about relative resistance and resilience of stability factors, the most popular group was group I with high indices in both resistance and resilience. Site 7 (Beongae wetland) and site 8 (Jangcheok reservoir) had the highest similarity in the result of cluster analysis using the surveyed benthic macroinvertebrates.

• Geophysics and Geophysical Exploration
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• v.1 no.3
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• pp.170-175
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• 1998

A systematic methodology is developed for the prediction of the lithology using electrofacies classification from wireline log data. Multivariate statistical techniques are adopted to segment well log measurements and group the segments into electrofacies types. To consider corresponding contribution of each log and reduce the computational dimension, multivariate logs are transformed into a single variable through principal components analysis. Resultant principal components logs are segmented using the statistical zonation method to enhance the quality and efficiency of the interpreted results. Hierarchical cluster analysis is then used to group the segments into electrofacies. Optimal number of groups is determined on the basis of the ratio of within-group variance to total variance and core data. This technique is applied to the wells in the Korea Continental Shelf. The results of field application demonstrate that the prediction of lithology based on the electrofacies classification works well with reliability to the core and cutting data. This methodology for electrofacies determination can be used to define reservoir characterization which is helpful to the reservoir management.

• Journal of agricultural medicine and community health
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• v.6 no.1
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• pp.61-67
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• 1981

This survey was undertaken to evaluate the status of clonorchiasis in Chang-gok Myun, Hong-Seong Gun adjacent to Yedang reservoir from Sept., 1980 to Oct., 1981. A total of 550 subjects (male 318, and female 232) were examined by cellophane-thick smear technique and formalin-ether method. In order to identify the intensity of the Clonorchis sinensis infection, Stoll's egg dilution counting method was also applied to the C. sinensis positive cases. The following results were obtained in this survey; 1. In the examination of 550 subjects, Clonorchis sinensis eggs were found in 167 cases (30.4%). Male subjects showed 43.4% positive rates and female represented 12.5%. 2. The highest prevalence rate of Clonorchis sinensis was found in 40~49 year group in male (64.2%) and 30~39 year group in female (22.0%), although 14.3%~16.7% positive rates were found in young aged group. 3. Mean E.P.G. of Clonorchis sinensis infected cases were 6,148, showing 7,533 in male and 5,193 in female. 4. The degree of intensity of Clonorchis sinensis infection by E.P.G. count was distributed as 30.4% in light infection (1~999), 45.7% in moderate infection (1,000~29,999) and 5.8% in very heavy infection (over 30,000) in male. Female showed 48.3% in light, 37.9% in moderate, 10.3%. in heavy and 3.5% in very heavy infection. 5. Other helminthic infection rate was 15.6% in Ascaris lumbricoides infection, 15.1% in Trichuris trichiura infection and 4.4% of male subjects showed eggs of Taenia species.

• Journal of Wetlands Research
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• v.19 no.2
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• pp.223-229
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• 2017

This study analyzed the relationship between environmental factors and the temporal changes of the bird populations during the every January from 1999 to 2016 (18 years) in Donglim reservoir. 'Winter Waterbird Census of Korea' data by National Institute of Biological Resources were used for the bird population data, and principal component analysis and cluster analysis were used to analyze the changes of annual population. The average temperature of January and the average storage rate of the reservoir were used as environmental factors. According to the results of the study, the population changes in the study area can be explained by the increase and decrease of two water bird groups and a mountain bird group. The average temperature of the years when the population of water bird groups increased was more than $1.4^{\circ}C$ in comparison with the year when mountain birds increased. On the other hand, the influence of the water content was not clear. The visiting of Baikal Teal affected by temperature was a factor affecting the other group of water bird and a mountain bird group. The results of this study suggest that the temperature change affects the global spatial distribution of birds and the migration of large population species such as Baikal Teal affects species composition and populations of birds at local scale. Therefore, understanding of environmental changes at large scale and spatial distribution of species and flock contributes to understand the temporal variation of the bird population at regional or local scales.

• Korean Journal of Ecology and Environment
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• v.51 no.2
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• pp.160-167
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• 2018

The role played by reservoirs in the biogeochemical cycles of elements is a subject of ongoing debate. Recent research has revealed that reservoirs emit significant levels of greenhouse gases. To assess the importance of reservoirs in monsoon climate areas as a source of methane gas into the atmosphere, we investigated variations in organic carbon (OC) input into the reservoir, oxic state changes, and finally the amount of methane emitted (focusing on the ebullition pathway) in Lake Soyang, which is the largest reservoir in South Korea. Total organic carbon (TOC) concentrations were higher during summer after two years of heavy rainfall. The sedimentation rates of particulate organic carbon (POC) and particulate organic nitrogen (PON) were higher in the epilimnion and hypolimnion than the metalimnioin, indicating that autochthonous and allochthonous carbon made separate contributions to the TOC. During stratification, oxygen depletion occurred in the hypolimnion due to the decomposition of organic matter. Under these conditions, $H_2S$ and $CH_4$ can be released from sediment. The methane emissions from the reservoir were much higher than from other natural lakes. However, the temporal and spatial variations of methane ebullition were huge, and were clearly dependent on many factors. Therefore, more research via a well-organized field campaign is needed to investigate methane emissions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.5 no.3
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• pp.71-75
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• 1972

The growth of the mussel, Mytilus edulis, in a salt-field reservoir was investigated at Dangjin, Choongnam, from June to October in 1970. l. Temperature, salinity, specific gravity, and pH of water were $22.5-27.5^{\circ}C,\;28.6-34.8\%$, 1.019-1.024, and 7.6 respectively in the salt-field reservoir from June 20 to July 19. 2. Three species of Gastropoda and seven species of Pelecypoda were collected. 3. The shell height of the mussel group in the highest abundance increased from 200mm($15\~25mm$) on June 15 to 40mm ($20\~50mm$) on September 26 in the salt-field reservoir, whereas the average shell heights of them were 19.80mm (June 15) and 35. 10mm (Sept. 26) respectively. 4. The daily growth of the mussel from July 10 to August 12 was 0.22 mm in shell height and highest during the experimental period. 5. The relationships between shell length (L) and shell height (H), and between shell length (L) and shell breadth (B) of the young mussel are represented by the following equations respectively : H=1.26776L+5.07978 B=35041L+3.05502 6. From the above results, it is suggested that the culture of the mussell, Mytilus edulis, in a salt-field reservoir is possible.

• Journal of Environmental Science International
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• v.19 no.11
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• pp.1407-1421
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• 2010

This study was carried out to elucidate the relation between water quality and structure of the aquatic ecosystem in the agriculture reservoir Otae-ji from January to December in 2009. The proportion of forest was 46.98%, which means that non-point sources are major contributor of water pollution in this area. The annual mean COD(Chemical Oxygen Demand) in Otae-ji was $3.6mgL^{-1}$, indicating, level II of environmental standards and the trophic state was mesotrophic. Although total phosporus concentration in the reservoir was high in August due to large inflow of nutrients from outside the reservoir during monsoon season, there was no break out of significant algal bloom in the summer. The seasonal succession of phytoplankton showed that the dinophyta dominated in the the spring, chlorophyta in the summer, chrysophyta and chlorophyta in the autumn and chrysophyta in the winter. In case of zooplankton, rotifers dominated in the most seasons, but cladoceran(Bosmina longirostris) dominated in June and copepod(Nauplii) in August. The macrophyte plants showed diverse species compositon consisted of 3 varieties, 24 species, 23 genera, 15 families and 14 orders. The macroinvertebrates also showed various FFG(Functional Feeding Groups) such as GC(Gathering-Collector), P(Predator), SH(Shedder), FC(Filter-Collector) and PP(Plant-Piercer). Ecosystem stability analysis using aquatic insects was classified as Group I, which has high resilience and resistance indices. A total of 14 species of fish was collected but exotic species such as Lepomis macrochirus and Micropterus salmoides were not found in Otae-ji. In conclusion, the preservation of healthy food wed in the reservoir ecosystem is closely related to water quality management as well as effective prevention of algal bloom by helping good material circulation in aquatic ecosystems.