• Journal of Korean Society on Water Environment
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• v.31 no.3
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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.

• Journal of Korean Society on Water Environment
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• v.30 no.1
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• pp.44-59
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• 2014

Despite the implementation of TMDL, the water quality in lower watershed of Nam river dam has worsened continuously since 2005. Multifarious pollution sources such as cities and industrial districts are scattered around it. Nam river downstream bed slope is very gentle towards the downstream water flow of slows it down even more, depending on the water quality deterioration is accelerated eutrophication occurs. In this study, the mainstream in lower watershed of Nam river dam region to target aquatic organic matter by phytoplankton growth contribution was evaluated by statistical analysis. and statistical evaluation of water quality and the accuracy of forecasting, model calibration and verification procedures by completing QUALKO2 it's eutrophic phenomena that occur frequently in the dam outflow through scenarios predict an increase in water quality management plans to present the best should.

• Journal of Ecology and Environment
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• v.32 no.4
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• pp.221-227
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• 2009

This study describes time lag responses between hydrological variables and phytoplankton biomass in a regulated river system, the lower Nakdong River in South Korea. The lower Nakdong is a typical flow-controlled lotic system, and its limnological characteristics are influenced by climatic variation such as monsoons and summer typhoons. Mean rainfall in the area during summer is about 1,200 mm, which comprises >60% of annual rainfall. Our results show that the regulation of flow in the Nakdong by multi-purpose dams from 1995 to 2004 affected phytoplankton dynamics. Diatom blooms occurred in winter, when the limited discharge allowed for proliferation of the phytoplankton community. Using multiple regression analysis, we detected significant time-delayed relationships between hydrological variables and phytoplankton biomass. These results may be useful for water resource managers, and suggest that 'smart flow' control would improve water quality in large regulated river systems of the Republic of Korea.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.332-338
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• 2007

In this study the flow duration curves for Nakdong river basin are analyzed. The TANK model is used as a hydrologic simulation model whose parameters are estimated from 8-day intervals flow data measured by NIER Nakdong River Water Environment Laboratory. As a comparison result between generated natural and present river flow, the present river flow is higher than the natural river flow in the up- and mid-stream of Nakdong river, while the present river flow is lower than the natural river flow in the down stream of Nakdong river.

• 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 Korean Society on Water Environment
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• v.32 no.1
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• pp.52-59
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• 2016

This study investigated the occurrences and succession patterns of harmful cyanobacteria, as well as environmental factors, during a 3-year period (September 2012 to August 2015) in the upper region of the Nakdong River around Sangju weir. A total of 27 cyanobacterial taxa were observed in this study, and classified into 26 species and 1 variety belonging to 11 genera, 5 families, and 3 orders. Cell density ranged from 24 to 42,001 cells/ml, with a geometric mean of 33 cells/ml, during the survey period. The dominant orders differed depending on the survey year; order Oscillatoriales in 2013, Chroococcales in 2014 and Nostocales in 2015. An Aphanizomenon bloom occurred in June 2015 at which time the highest cell density of 36,873 cells/ml was detected in the upper region of the Nakdong River, where as the Aphanizomenon spp. cell density (190-1,704 cells/ml) had been low prior to that time. An Aphanizomenon bloom also occurred at around the same time downstream in the Young River, a major inflow branch of the Nakdong River. The Aphanizomenon cell density along the Nakdong River increased markedly after joining of the YoungRiver, indicating that the Aphanizomenon bloom in the YoungRiver caused a bloom in the Nakdong River. Meteorological and environmental parameters, such as very low precipitation, higher water temperature, pH, and TP concentration, and lower TN/TP ratio, in May and June of 2015 than in 2013 and 2014 exerted marked effects on the Aphanizomenon bloom in June 2015 in the Young River.

• Journal of Ecology and Environment
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• v.46 no.2
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• pp.99-110
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• 2022

Background: Many investigations on phytoplankton from the Nakdong River carried out. However, since the weirs were constructed, only changes in phytoplankton biomass and dominant species have been restrictively studied in phytoplankton investigations in the Nakdong River. Added to this, any investigation on the phytoplankton flora has not been done in the Nakdong River. The aim of this study is to elucidate the characteristics of phytoplankton communities in the Nakdong River with the weirs built in it. Results: We observed a total of 103 taxa of Euglenophytes belonging to 8 genera from middle-lower part of the Nakdong River. The genus Trachelomonas was the most abundant group making up 40 taxa, followed Lepocinclis (20), Phacus (17), Strombomonas (14), Euglena (5), Colacium (3), Monomorphina (3) and Menoideum (1). Among them, a total of 22 taxa including Colacium (1), Lepocinclis (8), Phacus (4), Strombomonas (4) and Trachelomonas (5) were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River. All the species are illustrated with photomicrographs, and new to Korean species briefly discussed with regard to their taxonomy together with photomicrographs. Conclusions: The present study, a total of 22 taxa including one species of Colacium, 8 taxa of Lepocinclis, 4 taxa of Phacus, 4 taxa of Strombomonas and 5 taxa of Trachelomonas were reported for the first time in Korea, and 86 taxa including those new to Korea were first recorded in the Nakdong River.

• Journal of Environmental Impact Assessment
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• v.17 no.3
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• pp.189-200
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• 2008

As a transition zone between terrestrial and aquatic ecosystems, riparian areas of rivers and streams play significant roles in production and decomposition for river and stream systems. Understanding of the physical and ecological characteristics of riparian areas are, therefore, important for the management of river and stream systems. It is especially important to understand the characteristics of riparian areas for the Nakdong River in Korea which has a large watershed area and diverse land uses. This study aimed at collecting field data, according to stream types, which are essential for the management of riparian areas of the middle and lower reaches of the Nakdong River, Korea. Most riparian areas surveyed in this study had roads within 100 meters from river edges. Distances from water edge to banks were less than 1m for most riparian areas neighboring agricultural lands, indicating that those areas might be very vulnerable to pollutant inputs from non-point sources. Water quality data indicated that soil erosion in the riparian areas could be a major source of phosphorus input to the Nakdong River and land use patters might have a significant influence on nitrogen concentration in the river. Heavy metal concentrations in soils of the riparian areas of the river were below soil quality standards, except arsenic and chromium. Vegetation surveys showed that therophytes were the most frequently occurred riparian plants in the Nakdong River. Number of aquatic plant species increased downstream, with the most diverse aquatic plants observed in wetlands and irrigation canals of the West Nakdong River. Occurrence rate of naturalized plants and urbanization index were high in the survey sites adjacent to urban and agricultural areas.

• Journal of Environmental Science International
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• v.5 no.6
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• pp.801-812
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• 1996

We investigated concentrations of heavy metals(Cr, Cd, Zn, Fe, Pb, Cu, and Mnl and correlations between concentrations of heavy metals in the sediment, soil, weeds, and vegetables on the lower Nakdong river. Concentrations of heavy metals on the lower Milyang river was generally lower than those of other sampling area. In the soil, concentration of Pb is generally larger than that of other heavy metals. Generally, concentrations of heavy metals in the sediment show decreasing tendency 8s the sampling area moves toward downstream of the river, but those of in the soil and weeds show increasing tendency. There is no significant correlation between concentration of heavy metals in the soil-sediment, soil-vegetables, sediment-weeds, or vegetables-weeds. Only concentrations of Pb in the vegetables and those of in the weeds show very high correlation.