• 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.

• Journal of Korean Society on Water Environment
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• v.33 no.6
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• pp.640-649
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• 2017

The purpose of this study is the analysis of the water quality spatial characteristics for the main stream of Nakdong River in consideration of the tributary inflow. The flow and water quality (BOD, TOC, TP) data for 32 monitoring stations located in the main stream and the tributaries of Nakdong River were collected from 2003 to 2016. From the results of the flow and water quality analyses for each site, a status map of the flow and the water quality for Nakdong River was produced. The water quality of each river section was classified according to seven river-environment standards. The water quality changes in the main stream before and after the confluence were analyzed spatially. As a result, the water quality of Kumho River, in particular the Kumho B to Kumho C section, is the worst among the tributaries. In addition, the water quality grades of the lower streams such as Nam River and Miryang are worse than that of the upper streams of the Nakdong River. In the case of the main stream, the water quality grades of the sections between the Wicheon and Nam River confluences and the section from Nakbon L to Nakbon N are relatively poor.

• Journal of Environmental Health Sciences
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• v.9 no.1
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• pp.49-62
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• 1983

Evaluation of water quality of Yeong San river and Seomjin river by using of newly simplified MBOD method was performed. Of course, thought that there is some differences between nutrient demands of heterotrophic bacteria and those of Algae which obtain it by photosynthesis, but it has little influence on evaluation of Algae Growth potential. The result of this study were as follows: 1) In both river, the value of Chemical analysis and MBOD method of inorganic salts reveals as nearly same result. 2) Though organic pollution of Seomjin river is less than that of Yeongsan but inorganic contamination is somewhat advanced BOD 2.8 ppm. and MBOD 340 ppm. in Seomjin river but BOD 22 ppm. and MBOD 480 ppm. in Yeongsan river. 3) Both river have tendency to reveal higher Nitrogen value is MBOD=MBOD -P

• Korean Journal of Hydrosciences
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• v.10
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• pp.73-83
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• 1999

The intake towers of Buyeo W.T.P. in Keum river have being suffered from the sedimentation problems since the beginning of the operation. Impellers of the intake pumps have to the frequently changed due to the serious surface erosion. Thousands tons of sands are entrapped in the intake towers and equalization chambers of W.T.P. every year. Site surveying and numerical analysis were carried out to suggest an appropriate solution by understanding the general sedimentation regime of Keum river and causes of the sedimentation in the intake towers. Origin of the sediment could be found by the desk and site inspections. The validity of the used numerical models was examined by comparisons between the calculated bydraulic values and the measured ones during the specific periods. The design flow rate for the prediction of the future sedimentation regime of the rever was studied. The efficiency of the sediment control measures was also examined with the verified numerical models. Finally, it was found that the best solution could be a combination of three sediment control measures; increase the clearance between river bed and inlet, construct jetties at 2 kilometers upstream from the intake towers, and put vanes at the right side of the intake towers.

• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.1
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• pp.118-129
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• 2011

This Study has developed the information system of the rivers based on 3D image GIS by converging the latest information technology of GIS(Geographic Information System), RS(Remote Sensing), GNSS(Global Navigation Satellite System), aerial laser survey(LiDAR) with real time network technology in order to understand the current situation of all the four major rivers and support the administrative management system. The said information system acquires the high resolution aerial photographs of 25cm, aerial laser survey and water depth surveying data to express precise space information on the whole Youngsan River which is the leading project site out of the four river sites. Monitoring the site is made available on the transporting means such as a helicopter, boat or a bus in connection with locational coordinate tracking skill for the moving objects in real time using GNSS. It makes monitoring all the information on the four river job sites available at a glance, which can obtain the reliability of the people to such vast areas along with enhancing the recognition of the people by publicity of four Rivers Revitalizing Project and reports thereof.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.561-573
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• 2012

The object of this study was to analyze long-term water quality gradients during 1992-2008 at six sites of Geumho River and near-by two sites of Nakdong River and their influences on fish trophic guilds and tolerance guilds along with ecological health. Water quality including biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, total phosphorus (TP), total nitrogen (TN), and total suspended solids (TSS) varied largely depending on the sampling locations and seasons. Values of ambient BOD, COD, TP, and TN were greater in the downstream than in the upstream reach, and seasonal and interannual variabilities were also higher in the downstreams. This phenomenon was evident due to a dilution by the Asian monsoon rainfall during the monsoon. These outcomes indicate that point sources near the downstream are important for the chemical conditions, but also seasonal stream runoff was considered as an important factor regulating the chemical conditions. Conductivity decreased rapidly during the summer due to ionic dilution, and nutrients (N, P), BOD, COD had an inverse function of seasonal precipitation. Based on the water quality, we selected two sites (control site = $C_s$ vs. impacted site = $I_s$) for impact analysis of water chemistry on fish community and trophic/tolerant guilds. Fish guild analysis showed that species diversity was higher in the headwater stream ($C_s$) than the impacted downstream ($I_s$), and that the proportion of tolerant and omnivore species were greater in the impacted site of downstream. Comparisons of water quality between Geumho River and Nakdong River indicated that Geumho River was considered as a point source which degradated water quality to the Nakdong River. Overall, chemical water quality and fish guild analysis suggest that even if current chemical quality got better after 1996 due to continuous constructions of wastewater disposal plants near the downstreams, fish compositions of tolerant and omnivores were still dominated the community. Thus, biological restoration based on ecological health is required for the ecosystem conservation.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.132-137
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• 2018

Compared with general rivers, fluctuations of the water level and the river bed are severe in the tidal river. In hydro-dynamic aspect, such fluctuation gives different river-bed data to us according to observing period. The time-dependent river-bed data and pre-estimation of the Manning's roughness coefficient which is the key factor of numerical modelling induces uncertainty of evaluating the design flood level. Thus it is necessary to pay more attention to calculate the flood level at tidal rivers than at general rivers. In this study, downstream of the Imjin River where is affected by tide of the West Sea selected as a study site. From the numerical modelling, it was shown that the unsteady simulation gave considerable mitigation of the water level from the starting point to 15 km upstream compared to the steady simulation. Either making a detention pond or optional dredging was not effective to mitigate the flood level at Gugok - Majung region where is located in the downstream of the Imjin River. Therefore, a more sophisticated approach is required to evaluate the design flood level estimation before constructive measures adopted in general rivers when establishing the flood control plan in a tidal river.

• Journal of the Korean GEO-environmental Society
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• v.18 no.1
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• pp.37-47
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• 2017

The Mekong River plays an extremely important role in Southeast Asia. Flowing through six countries, including China, Myanmar, Thailand, Laos PDR, Cambodia, and Vietnam, it is a site of great biological and ecological diversity and the habitat of numerous species of fish. It also supports a very large population that lives along the river basin. Therefore, much attention has been focused on the giant Mekong River Basin, particularly, its soil erosion and sedimentation problems. In fact, many methods have been used to calculate and simulate these problems. However, in the case of the Mekong River Basin, the available data is limited because of the extreme size of the area (about $795,000km^2$) and lack of equipment systems in the countries through which the Mekong River flows. In this study, we applied the Universal Soil Loss Equation (USLE) model in a GIS (Geographic Information System) framework to calculate the amount of soil erosion and sediment load during the selected period, from 1951 to 2007. The result points out dangerous areas, such as the Upper Mekong River Basin and 3S Basin (containing the Sekong, Sesan, and Srepok Rivers) that are suffering the serious consequences of soil erosion problems. Moreover, the present model is also useful for supporting river basin management in the implementation of sustainable management practices in the Mekong River Basin and other basins.

• The Korean Journal of Ecology
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• v.24 no.4
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• pp.253-258
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• 2001

Land use pattern in the Wangsuk river watershed was investigated on the bases of physiognomic vegetation maps made from the aerial photograph interpretation and field check. Landscape structure was analyzed using a GIS program supported by ArcView. Landscape structure depended on the geographical position of the river, such as the upper, middle and lower river. Watersheds of the upper and middle rivers were dominated by forests composed of secondary forest and plantation. But agricultural fields dominated that of the middle and lower river. Urban area and agricultural fields increased in from the upper toward the lower river watersheds. In addition to, a transformation of agricultural pattern into an institutional agriculture was characteristic in the middle and lower river basins. Water qualities of the Wangsuk river were usually better in the order of the upper, middle, and lower river, but they were fluctuated according to the site. Such fluctuation would due to self-purification of the river and land use pattern of the watershed as the non-point source. In this viewpoint, a strategy to manage the water quality in the level of watershed is urgently required.

• Journal of Korean Society on Water Environment
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• v.29 no.2
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• pp.155-164
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• 2013

To confirm the relationship between climate change and Stephanodiscus in Mulgeum station of Nakdong River, Korea, this study was conducted. The temperature in crease by climate change was observed in the study site, where the temperature was gradually increased in most seasons, except for summer season. The mass proliferation of Stephanodiscus constantly appeared in every year, especially between November and March, and when Stephanodiscus abundance was above 90% in phytoplankton biomass. Among this period, phytoplankton biomass was high related with water temperature ($r^2$=0.249, P<0.01) than nutrient factors such as nitrogen and phosphorus in the study site. Finally, temperature by climate change can be regarded as the affecting factor for chl. a variation, because temperature was strongly related with water temperature ($r^2$=0.748, P<0.01). From 1997 to 2010, the annual maximum phytoplankton biomass was recorded in the range of temperature from $4.8^{\circ}C$ to $8.4^{\circ}C$, and the range was regarded as the temperature condition for the optimal growth of Stephanodiscus in the study site. On the optimal growth temperature, the trend of monthly average temperature corresponded to the trend of chl. a variation from November to March. In future, the increase of temperature by climate change can prolong Stephanodiscus blooming period in winter and spring seasons.