• 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 Korean Society on Water Environment
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• v.29 no.4
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• pp.540-550
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• 2013

Temporal increase of SS induces concentrations in various forms of organic matter including BOD, COD, TOC. Consequently, it causes hard to identify sources of water pollution during or after precipitation. The objective of this study is to investigate variations of DOC concentration caused by increase of flow and changes of external factors in river by comparing to SS concentration. In results, monitoring sites (e.g., Banbyeonchen) consisting of hard riverbed showed high correlation between SS and organic matters, except BOD. On the contrary, other sites (e.g., Naesungcheon) where riverbed consists of sand were found in a wide range of annual fluctuation in SS level, whereas these sites showed a narrow range in annual DOC fluctuation. In Gumhogang and Namgang, a lower correlation between SS and other factors was found most likely because of high concentration in organic matter. However, lower annual fluctuation values of DOC were observed in comparison to those of COD and TOC. Similar results were also confirmed in main river sites, Sangju and Mulgeum. In conclusion, DOC concentration is better indicator for monitoring organic matter which cannot be provided by BOD, COD, TOC in the Nakdong river basin.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.3
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• pp.325-335
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• 2015

Concerns about water quality in the Nakdong River have been raised because the Nakdong River will change from a lotic environment to a lentic environmental due to the installation of eight weirs to be constructed as part of the Four Major Rivers Restoration Project. The rapid urbanization and industrialization of the middle and the lower reaches of Nakdong River causes the indiscreet discharge of uncleanly living sewage and industrial wastewater. And the water quality of lower reaches of Nakdong River is getting seriously worse. Owing to the water shortage of Nakdong River and the closing of reaches because of the estuary dyke in the dry season, the velocity of a moving fluid is almost accumulated under 0.03m/sec. Then a pollutant is piled up on the bottom of the river. Polluted sediment is formed and nutrition level of water is increased more and more. The eutrophication state propagated to dark brown or green from eutrophication often comes out. Therefore in this study, we measured Chl. a of chlorophyll sensor (YSI6600V2) and aceton extraction through field observation in the Nakdong River and Samrangjin. And we evaluated the reliability of chlorophyll sensor. In correlation analysis between chlorophyll sensor and aceton extraction, it shows high relation in general. And it also shows high relation among the chlorophyll sensor and aceton extraction of the dominant diatom (Skeletonema costatum), Dinophyta (Prorocentrum minimum) in the Nakdong River estuary by laboratory analysis results.

• Journal of Environmental Science International
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• v.26 no.8
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• pp.939-953
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• 2017

For the development of flow duration curves for the management of 41 Total Maximum Daily Load (TMDL) units of the Nakdong River basin, first, an equation for estimating daily flow rates as well as the level of correlation (correlation and determination coefficients) was extrapolated through regression analysis of discrete (Ministry of Environment) and continuous (Ministry of Land, Infrastructure and Transportation) measurement data. The equation derived from the analysis was used to estimate daily flow rates in order to develop flow duration curves for each TMDL unit. By using the equation, the annual flow duration curves and flow curves, for the entire period and for each TMDL unit of the basin, were developed to be demonstrated in this research. Standard flow rates (abundant-, ordinary-, low- and drought flows) for major flow duration periods were calculated based on the annual flow duration curves. Then, the flow rates, based on percentile ranks of exceedance probabilities (5, 25, 50, 75, and 95%), were calculated according to the flow duration curves for the entire period and are suggested in this research. These results can be used for feasibility assessment of the set values of primary and secondary standard flow rates for each river system, which are derived from complicated models. In addition, they will also be useful for the process of implementing TMDL management, including evaluation of the target level of water purity based on load duration curves.

• Journal of Environmental Science International
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• v.24 no.8
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• pp.969-980
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• 2015

In order to certificate the distribution and pollution of heavy metal of surface sediments in Nakdong River were collected and analyzed for grain size, water content, ignition loss and heavy metal content. Surface sediments mainly composed of sand(avg. 94.6%) and water content and ignition loss were 20.46%, 1.53% on average. Grain size were relatively fine and organic matter content were relatively high in the Hoichun and Sunakdonggang. Most of heavy metal content(Zn > Cr > Pb > Ni > Cu > Hg) in the Deokcheongang and Sunakdonggang were higher than the other streams. The Igeo were non polluted(less than 0) in all streams and the EF were relatively high in the small stream and PLI were non polluted(less than 1). In addition, organic matter, heavy metal content and pollution were highly correlation with grain size. Surface sediments in study area, heavy metal pollution of the Sunakdonggang were relatively high compared to the other stream but these results were not serious pollution that exceed the sediment pollution evaluation standard of river and lake in Korea and pollution levels adversely affected the majority of benthos were not.

• Journal of Environmental Science International
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• v.26 no.5
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• pp.549-561
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• 2017

Recently IPCC (International Panel on Climate Change, 2007) pointed out that global warming is a certain ongoing process on the earth, due to which water resources management is becoming one of the most difficult tasks with the frequent occurrences of extreme floods and droughts. In this study we made runoff predictions for several control points in the Geum River by using the watershed runoff model, SSARR (Streamflow Synthesis and Reservoir Regulation Model), with daily RCP 4.5 and RCP 8.5 scenarios for 100 year from 1st Jan 2006 to 31st Dec 2100 at the resolution of 1 km given by Climate Change Information Center. As a result of, the Geum River Basin is predicted to be a constant flow increases, and it showed a variation in the water circulation system. Thus, it was found that the different seasonality occurred.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.723-735
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• 2014

Sediment discharge by long-term runoff in the Nakdong River watershed should be predicted for the maintenance and management of the Nakdong River newly changed by the four major river restoration project. The data establishment by the analysis of runoff and sediment discharge using the long-term watershed model is necessary to predict possible problems by incoming sediments and to prepare countermeasures for the maintenance and management. Therefore, sediment discharges by long-term runoff in the main points of the Nakdong River were calculated using SWAT(soil and water assessment tool) model and the relations and features between rainfall, runoff, and sediment discharge were analyzed in this study. As a result of sediment discharge calculation in the main points of the Nakdong River and tributaries, the sediment discharge at the outlet of the Naesung Stream was greater than the Jindong Station in the Lower Nakdong River from 1999 to 2008 except the years with low precipitation. The sediment discharge at the Nakdong River Estuary Barrage (NREB) was corresponding to 20% of the Jindong Station which is located about 80 km upstream from NREB.

• Journal of Korean Society on Water Environment
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• v.31 no.3
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• pp.286-294
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• 2015

Temporal and spatial characteristics of cyanobacterial communities at the monitoring stations for Harmful Algal Bloom Alert System (HABAS) in Nakdong River and Lake Dukdong were investigated for two years (2013 to 2014). A total of 30 cyanobacterial species from 14 genera were found at the survey stations. Microcystis sp. showed maximum cell density in the total cyanobacterial community in August, 2014 at ND-2 and in September, 2013 at ND-3 station. Lynbya limnetica and Geitlerinema sp., non-target species for alert criteria showed maximum cell density at ND-1 (August, 2013) and Dam station of Lake Dukdong (September, 2014), respectively. Total cyanobacterial cell density and the relative abundance of four target genera (Microcystis, Anabaena, Aphanizomenon and Oscillatoria spp.) for alert criteria was relatively lower in the mesotrophic Lake Dukdong than at the eutrophic riverine stations of Nakdong River, indicating cyanobacterial density and the RA of target genera is affected by the trophic state of the monitoring stations. Simulating the alert system using phycocyanin concentration as an alert criterion resulted in the longer period of alert issued compared to the period of alert issued using the current criterion of harmful cyanobacterial cell density due to the influence of phycocyanin concentration from non-target cyanobacterial species.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.210-215
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• 2004

The Purpose of this study are to develop the simulation(Tank model, Rainfall-runoff model) for the estimation of wily river discharge and for evaluation of wily pollutant loads from the watersheds of the objected basin area. As apply this constructed Tank model to Nakdong river region, we evaluated the wily river discharge of Nakdong river from use-land conditions, precipitation and evaporation data of 3 years(from 1998 to 2000) and investigate the seasonal fluctuation of SS, COD, TN, TP inflowing into Nakdong river. The result shows that summer has high pollutant level than winter in seasonal characteristic and the down stream has high pollutant level than the upper stream. The annual average of SS, COD, TN, TP flawing in Nakdong river(Samranjin) was estimated each 691ton-COD/year, 1854.2ton-SS/year, 382.8ton-TN/year and 13.0ton- TP/year.

• Journal of Environmental Science International
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• v.17 no.8
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• pp.833-840
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• 2008

Deoxygenation process in which CBOD(carbonaceous BOD) is biochemically oxidized to reduced inorganic compounds is of great significance in the oxygen demand of stream waters. The CBOD decay rate has traditionally been determined in a laboratory by CBOD bottle incubation method. But in this study, CBOD decay rates were obtained by laboratory incubation method and natural waters experiment. Average CBOD decay rate for the Nakdong river(upper zone) in natural waters were 0.553 $day^{-1}$ during April 2005 to January 2007. The values in the middle and down parts of the Nakdong river in natural waters were 0.384 $day^{-1}$ and 0.252 $day^{-1}$ at the same period of time, respectively. Average CBOD decay rates using by incubation method in the upper/middle/down parts of the main stream in the Nakdong river basin was 0.270 $day^{-1}$, and 0.289 $day^{-1}$, and 0.283 $day^{-1}$ during April 2005 to January 2007, respectively.