• 생태와환경
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• 제38권spc호
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• pp.44-53
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• 2005

The Nakdong River, which lies in a monsoon climate zone with warm rainy summers and cold dry winters, is a typical ecosystem showing the attributes of a regulated river. In 2003, the total annual rainfall (1,805 mm) was higher than the average of the past nine years from 1994 to 2002 (1,250 mm). In September a powerful typhoon, Maemi, caused a big impact on the limnology of the river for over two months. Among the limnological variables, turbidity in 2003 (37.4 ${\pm}$ 94.1 NTU, n = 54) was higher than the annual average for ten years (18.5 ${\pm}$ 2.3 NTU, n = 486) in the lower part of the river (Mulgum: RK 28). Furthermore, physical disturbance (e.g. stream bank erosion within channel) in the upstream of the Imha Dam (RK ca. 350; river distance in kilometer from the estuary barrage) in the upper part of the river was a source of high turbidity, and impacted on the limnological dynamics along a 350 km section of the middle to lower part of the river. After the typhoon, high turbidity persisted more than two months in the late autumn from September to November in 2003. Flow regulation and the extended duration of turbid water are superimposed on the template of existing main channel hydroecology, which may cause spatial changes in the population dynamics of plankton in the river.

• 한국물환경학회지
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• 제31권3호
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• pp.304-312
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• 2015

In this study, we tried to determine the vertical variation of sediment structure and geochemical characteristics, core sediment was collected in the Nakdong River midstream on August, 2014. Core sediment mainly composed of sand (51.48%) and silt (46.21%) and coarsing upward changed from sM to mS facies. IL and TOC were decreased from lower to upper layer. C/N ratio was lower than 10 so the organic matters were originated from underwater creatures and C/S ratio was decreased from lower to upper layer. Heavy metal (Al, Fe, Zn, Cr, Pb, Ni, Cu, Cd) content were decreased from lower to upper layer and seriously polluted condition is not. These results are thought to be due to the effect of natural and anthropogenic in the fluctuation of flow.

• 한국물환경학회지
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• 제33권1호
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• pp.78-89
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• 2017

Water quality monitoring network data is being affected continuously due to non-point source pollution arising from agricultural land located on the Gwangsancheon outlet in the Nakdong River basin. In this study, we have performed analysis of water quality monitoring system, water quality pattern using SOM and water quality in the Gwangsancheon for sub-basin located at Gisan-myeon in the Nakdong River basin. We have developed and applied the model to estimate the runoff and non-point source loading. As a result of SOM pattern, the effect of non-point source pollution was the largest in the paddy fields and fields. As a result of the developed model, we found contribution rate and reduction rate for non-point source loading according to change of landuse because the reduction effect of nonpoint pollutants was 20.9% of SS, 9.9% of TN, 21.2% of TP and 8.9% of TOC depending on the landuse change.

• 물과 미래
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• 제24권1호
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• pp.83-92
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• 1991

본 연구는 금강유역의 주요수위표 지점에서 하천유지유량을 산정하는데 그 목적이 있다. 하천유지 유량을 산정하는 방법에는 수요적인 측면과 공급적인 측면 두가지로 분류할 수 있다. 본 논문에서 하천유지유량의 개념은 평균갈수량과 환경보존유량중 큰 값으로 결정하였다. 하천유지유량의 산정에서 대청댐 상류지역은 평균갈수량으로, 대청댐 하류지역은 평균갈수량과 QUAL2E 모형으로 산정된 수질보전유량값 중 큰 값을 하천유지유량으로 결정하였다. 그 결과 대청댐 하류인 공주와 규암지점 모두 평균갈수량 값이 크게 나타났으며 그 값은 공주지점에서 33.82$m^3$/sec, 규암 지점은 51.51$m^3$/sec 이였다. 그러므로 금강유역의 하천유지유량의 산정은 평균갈수량으로 결정하는것이 타당하다고 판단되었다.

• 한국환경농학회지
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• 제31권4호
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• pp.328-343
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• 2012

BACKGROUND: For effective subwatershed management, it is very important to select the tributaries for improving water quality and understand the characteristics of tributaries. Until now, however, the case study of main streams has been managed. 17 tributaries in Geum river subwatershed were monitored to regulate the source of water contaminations and identify their current situations in this study. METHODS AND RESULTS: As pollution indicators, such as biological oxygen demand($BOD_5$), chemical oxygen demand($COD_{Mn}$), suspended solid(SS), total nitrogen (T-N), total phosphate(T-P) and total organic carbon(TOC) in Geum river were examined from January to December in 2011. The results were as follows : The annual average concentration of nutrients in Yongdam reservoir upsteam was 0.7 mg/L for BOD, 3.0 mg/L for COD, 8.4 mg/L for SS, 2.905 mg/L for T-N, 0.035 mg/L for T-P and 1.6 mg/L for TOC. Water quality of Daechung reservoir upstream was mostly similar tendency in comparison to Yongdam reservoir upstream. Among the 22 tributaries, water quality in Daechung reservoir downstream was more polluted. T-N contents were significantly high in Miho B4 located Daechung reservoir downstream(annual average concentration: 13.53 mg/L). In cases of Miho A1, A2 and C1, pollution degree was worsened during rainy season expecially. CONCLUSION(S): For improving water quality of Geum river subwatershed, the tributaries in the Mihocheon area should be preferentially considered. Mihocheon tributary is the highest in pollution site, and thus a study on long-term effects should be research.

• 한국물환경학회지
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• 제30권4호
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• pp.441-451
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• 2014

Streamflow is typically divided into two components that are direct runoff and baseflow, it is required to analyze and estimate behaviors of those two flow components to understand watershed characteristics so that watershed management plan can be effective in pollutant reductions. Since pollutant load behaviors in a stream or river are variable by flow component behaviors, best management practices need to be applied in a watershed based on the pollutant load behaviors varying with flow components. Thus, baseflow behaviors were analyzed separating baseflow from streamflow data collected from fifteen streamflow gaging stations in the 4 major river watersheds which are the Han river, Nakdong river, Guem river, and Yeongsan Somjin river watersheds. Moreover, precipitation trends throughout the 4 River Systems were investigated, thus daily precipitation data were collected from sixty-five locations. The Hank river watershed displayed the largest precipitation (925.2 mm) in summer but the lowest precipitation (71.8 mm) in winter, indicating the watershed has the most fluctuating precipitation characteristic. While the precipitation trends in the Four River Systems varied, a distinct feature in baseflow trends was not found, moreover baseflow percentages to streamflow were typically greater than 50% in the Four River Systems. As shown in this study, it would be expected significant amount of pollutants could be contributed to the stream in the form of baseflow at the watershed.

• 상하수도학회지
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• 제29권3호
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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.

• 한국습지학회지
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• 제4권1호
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• pp.43-50
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• 2002

The channel improvement plan has contributed to the flood damage reduction studies and the plan has mainly performed by the levee construction which creates the cut river. The cut river has mainly used as the agricultural and housing purposes. Recently, however, it is considered as a natural wetland for the purposes of a flood control and preservation of nature. So, this study compares the economical benefits according to the purposes of the cut river utilizations such as an agricultural, levee construction for flood damage reduction, and wetland. The study area is the downstream part of Kok-Neung stream which is a main tributary of Han river. The agricultural and levee construction benefits are estimated based on the 'Agricultural and Forestry Statistical Year' (2000) and the 'Standard for River Design' (2001). The benefit or value for the wetland utilization of the cut river is estimated by the enquete using questionnaire. As a results, for the case of which the cut river is used as an agricultural land, the present net benefit is estimated as 195.81 million won, for the levee construction, as 20853.00 million won and for the wetland, as 24692.89 million won. Therefore, the wetland is the best choice for the cut river utilization.

• Journal of Ecology and Environment
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• 제37권1호
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• pp.1-11
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• 2014

To understand the effects of fluctuations in dam discharge due to river environments and phytoplankton communities, we monitored such environments and phytoplankton communities biweekly, from February 2001 to February 2002 and from February 2004 to February 2005, in the lower Han River (LHR), South Korea. The phytoplankton abundance during the dry season was approximately two times higher than that during the rainy season. In particular, fluctuations in diatom assemblages, which constituted over 70% of the total phytoplankton abundance, were affected severely by the changes in the discharge. When a large quantity of water in a dam was discharged into the LHR, the conductivity and the concentrations of total nitrogen (TN), total phosphorus (TP), and dissolved inorganic phosphorus (DIP) decreased rapidly, whereas the concentrations of suspended solids (SS), dissolved inorganic nitrogen (DIN), and dissolved silica (DSi) increased immediately. Time-delayed relationship also revealed that the dam discharge had an immediately significant negative relationship with phytoplankton abundance. On the whole, fluctuations in phytoplankton communities in the LHR were influenced much more by hydrodynamics such as dam discharge than by the availability of nutrients. Thus, the variability in these concentrations usually parallels the strength of river flow that is associated with summer rainfall, with higher values during periods of high river discharge.

• 대한지리학회지
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• 제46권3호
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• pp.304-318
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• 2011

본 연구는 우리나라에 분포하는 구하도의 유형을 구분하고 유형별 분포와 형상 특성을 분석하였다. 현재 우리나라에는 감입곡류 목 절단, 하천쟁탈, 분류, 감입곡류 하천의 인위적인 절단, 자유곡류 하도의 직강화, 분류 하도의 직강화에 의한 6가지 유형의 구하도가 총 409개 분포하고 있다. 이 가운데 266개로 가장 많은 감입곡류 목 절단 구하도는 고도가 높고 기복이 심하며 감입곡류 하천이 많은 강원과 경북에 많으며, 낙동강 본류의 상류, 남한강의 지류인 달천과 평창강 등에서 분포 빈도가 높다. 분류에 의한 구하도는 남한강 하류와 낙동강 하류의 본류, 자유곡류 하도의 직강화에 의한 구하도는 만경강과 영산강, 분류 하도의 직강화에 의한 구하도는 금호강에서 분포 빈도가 가장 높다. 감입곡류 목 절단과 하천쟁탈에 의한 구하도는 나머지 유형에 비해 해발고도와 하상비고가 매우 높아서, 농경지나 산림으로의 토지이용 비율이 상대적으로 높다.