• Journal of Environmental Science International
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• v.25 no.12
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• pp.1661-1671
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• 2016

Water quality in Nakdong river was analyzed using 699 monitoring data sets including flow rates and water quality concentrations collected at 195 tributary monitoring stations (the priority management areas: 35 stations, the non-priority management areas: 160 stations) in 2015. The highest average concentrations of all data for BOD, COD, T-N, T-P, SS, and TOC were 30~600 times higher than the lowest concentrations while the highest average loading rates were 800,000~2,700,000 times higher than the lowest loading rates. Because of the very large differences in the concentrations and loading rates, the variation of the concentrations and loading rates in a priority management monitoring station for BOD, T-P, and TOC was analyzed using the coefficient of variation, the ratio of the standard deviation value to the mean value. For BOD, T-P, and TOC, the coefficients of variation for concentration were mostly less than 100%, whereas the coefficients of variation for loading rate ranged from 31.1% to 232.2%. The very big difference in the loading rates was due to the large variation in flow rates. As a result of this, the estimation of water quality at each monitoring station using the average values of the concentrations and loading rates might be not rational in terms of their representativeness. In this study, new water quality analysis methods using all collected monitoring data were suggested and applied according to the water quality standard in medium-sized management areas.

• Journal of Life Science
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• v.22 no.8
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• pp.1041-1045
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• 2012

This study investigated the changes caused by diverting water applications at the riverhead of the Onchun Stream via the monitoring of several water quality and biological parameters between 10/09 and 10/10. The analysis indicated that the Onchun Stream distinctly decreased in terms of several water quality parameters, such as BOD, COD, TN, TP, and the concentration of heavy metals as compared to similar values in 2005, before the flowing of the Nakdong River. Especially, BOD showed the 2nd grade of water quality, with an average of 2.0 mg/l at all sites. The species number and standing crops of plankton and benthic macroinvertebrates in the Onchun Stream were also increased. Thus, it was concluded that diverting water from the Nakdong River to the Onchun Stream dramatically improved various environmental indices, such as water quality and biological changes.

• Journal of Korean Society of Water and Wastewater
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• v.17 no.4
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• pp.487-494
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• 2003

In this research, water qualities of river water and bank-filtrate were compared for six months including winter season. The location studied was Galjon area, the downstream of the Nakdong river. The well for bank-filtrate was installed 40 m apart from riverside. Main analytic results of bank-filtrate and river water were summarized as followings; the average concentrations in bank-filtrate were turbidity 0.8NTU, TN 0.4mg/l, $BOD_5$, 0.1mg/l, $KMnO_4$ consumption 1.6mg/l, heterotrophic bacteria 350cfu/ml, Fe 0.5mg/l, Mn 0.99mg/l while the average concentrations in river water were turbidity 6.1NTU, TN 3.9mg/l, $BOD_5$, 3.6mg/l, $KMnO_4$ consumption 11mg/l, heterotrophic bacteria 1,640cfu/ml, Fe 0.28mg/l, Mn 0.04mg/l. Water quality of bank-filtrate was mostly shown a good results than it of river water excepting Fe and Mn. In even basic constituents such as water temperature and pH, bank-filtrate was very settled while river water was extraordinary changable and high. In case of nitrogen, especially, total nitrogen of river water was 3.9mg/l while it of bank-filtrate was 0.4mg/l and its reduction was very high. The reason is that $NH^+_4-N$ among total nitrogen in the river water is nitrified and then denitrified in soil layer when it is pumped up as bank-filtrate. But Fe and Mn caused by the characteristics of soil was very high in bank-filtrate while Mn in river water was particularly very low and settled. As the distance between riverside and well was longer, concentration of Fe and Mn may be went up while its bacteria may be reduced.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.277-287
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• 2006

Production loads of the contaminants near the Nakdong-river are, BOD : $1,006ton{\cdot}day^{-1}$, TN : $117ton{\cdot}day^{-1}$, and TP : $21ton{\cdot}day^{-1}$. Among the sources of contamination, the biggest contribution to the production load was shared by the human population, which maintains 40.7% of BOD, 44.2% of TN, and 52.5% of TP production. Similarly, among the sources of discharge load, the human population contributed 45.0% of BOD, 34.5% of TN, and 45.8% of TP. Results of flow investigation in 2001 and 2002 indicate that among the side streams, Nam-river showed the greatest average flow. In case of main stream flow, it was increased in the downstream due to the increase of the influents from the side streams. In case of BOD, COD, TOC and SS, high values were detected at Keumho-river where industrial wastewater was discharged as high level concentration. In case of the main stream, Koryoung point where direct influence of Keumho-river and Seongseo industrial complex is evident showed high BOD, COD and TOC. Oxidized nitrogen compounds and total nitrogen showed similar patterns of BOD, COD, and TOC. Especially, nitrate nitrogen was relatively high at all points. However, in case of Chlorophyll-a, relatively high values were observed at mid- and downstream areas such as Koryoung, Namjee, Soosan, Moolkeum and Hakooeun. This could be caused by the slow flow rate and the abundant nutrient salts attributed by the side streams. Relatively better water quality was observed in 2002 when the flow was relatively abundant than that in 2001. Results of investigation during 2001-2002 showed that delivery load increased as the flow reaches downstream. In 2001, delivery loads at the downstream Soosan-bridge were BOD $22,152ton{\cdot}day^{-1}$, COD $45,467ton{\cdot}day^{-1}$, TN $22,062ton{\cdot}day^{-1}$, TP $926ton{\cdot}day^{-1}$. Delivery loads in 2002 were increased due to the increase of the rainfall. They are BOD $25,876ton{\cdot}day^{-1}$, COD $64,200ton{\cdot}day^{-1}$, TN $41,101ton{\cdot}day^{-1}$, and TP $1,362ton{\cdot}day^{-1}$.

• Journal of Environmental Science International
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• v.5 no.3
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• pp.377-385
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• 1996

This study aims at the estimation of a river management flow in urban basin analyzing Sinchun basin to be the tributary of Kumho river basin. The river management flow has to satisfy a low flow as natural flow and an environmental preservation flow estimated by a dilution flow to satisfy a target water quality in drought flow. Therefore for the estimation of a river management flow in Sinchun in this study, first Tank model as a basin runoff model estimates a low flow, a drought flow from a flow duration curve in Sinchun, second QUAL2E model as water quality model simulates water quality in Sinchun and estimates environmental preservation flow to satisfy a target water qua%its, BOD 8 mg/l by a dilution flow derived from Kumho river, Nakdong river and around water. And the river management flow is estimated by addition of a use flow and a loss flow to more flow between a low-flow and an environmental preservation flow.

• Journal of Environmental Impact Assessment
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• v.28 no.2
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• pp.169-182
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• 2019

This study assessed biological water quality using epilithic diatoms in the Yeong river, Naeseong stream and Wi stream in the upper region of the Nakdong river from May to October 2016. Epilithic diatoms were not mobile, so they could reflect long-term water quality. The sampled epilithic diatoms were identified a total 158 taxa which were composed to 2 orders, 3 suborders, 8 families, 34 genera, 143 species and 15 varieties. Dominant species were Achnanthes convergens and Achnanthes minutissima at Yeong river, Nitzschia inconspicua at Naeseong stream, and Achnanthes minutissima, Cocconeis placentula var. lineata and Navicula minima at Wi stream. As a result of the CCA, Electrical conductivity, total nitrogen and total phosphorus were important factors determining the diatom species composition in the upper region of the Nakdong river. The correlation between diatom indices (DAIpo & TDI) measured to be high in the correlation coefficient (0.87) from the result of correlation analysis. In the result of the assessment of biological water quality using DAIpo and TDI, Yeong river was rated as class A at most sites. Naeseong stream was rated as class C to D at all sites except for N1 which was rated as Class A. Wi stream was rated as class B to C for DAIpo of W1, and TDI was rated as class D. The assessment of biological water quality at this site showed inferior TDI result compared to that of DAIpo. DAIpo and TDI of W2 were rated as class A to D, and the water quality has changed a lot. W3 and W4 were mostly rated as class B and C respectively.

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.830-840
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• 2011

Climate change has been settled as pending issues to consider water resources and environment all over the world, however, scientific and quantitative assessment methods of climate change have never been standardized. When South Korea headed toward water deficiency nation, the study is not only required analysis of atmospheric or hydrologic factors, but also demanded analysis of correlation with water quality environment factors to gain management policies about climate change. Therefore, this study explored appropriate monthly rainfall elasticity in chosen 41 unit watersheds in Nak-dong river which is the biggest river in Korea and applied monitored discharge data in 2004 to 2009 with monthly rainfall using Thiessen method. Each unit watershed drew elasticity between water temperature and water quality factors such as BOD, COD, SS, T-N, and T-P. Moreover, this study performed non-linear correlation analysis with monitored discharge data. Based on results of analysis, this is first steps of climate change analysis using long-term monitoring to develop basic data by Nak-dong river Environmental Research Center (Ministry of Environment) and to draw quantitative results for reliable forecasting. Secondary, the results considered characteristic of air temperature and rainfall in each unit watershed so that the study has significance its various statistical applications. Finally, this study stands for developing comparable data through "The 4 major river restoration" project by Korea government before and after which cause water quality and water environment changes.

• 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 Environmental Science International
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• v.9 no.6
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• pp.455-462
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• 2000

This study aims at the development of the model for a forecasting of water quality in river basins using artificial neural network technique. Water quality by Artificial Neural Network Model forecasted and compared with observed values at the Sangju q and Dalsung stations in Nakdong river basin. For it, a multi-layer neural network was constructed to forecast river water quality. The neural network learns continuous-valued input and output data. Input data was selected as BOD, CO discharge and precipitation. As a result, it showed that method III of three methods was suitable more han other methods by statistical test(ME, MSE, Bias and VER). Therefore, it showed that Artificial Neural Network Model was suitable for forecasting river water quality.

• Journal of Korean Society on Water Environment
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• v.27 no.3
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• pp.349-356
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• 2011

This study, which evaluated the contribution of the real economic value and system in the Nakdong River Basin, estimated the emergy analysis for environmental accounting of the TMDL program. And an environmental accounting for TMDL is evaluated before and after adopting TMDL program respectively. The value of emergy after adopting the TMDL was 7.90 E+20 sej/yr. Although the real yield of the river after governmental investment was high (before: 9.7118 E+20 sej/yr and after: 9.7224 E+20 sej/yr), the effects of improvement was not great, in terms of an investment cost. The benefit/cost ratio resulted from environmental accounting has decreased from 1.493 to 1.230 due to the cost of managing treatment facilities. The method of improving water quality in the Nakdong River Basin by the TMDL program should be changed into an ecological treatment facilities using resources efficiently from a control of water quality depending on expansion of the wastewater treatment facilities and advanced treatment plant using high cost and non-renewable energies.