• Korean Journal of Ecology and Environment
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• v.38 no.spc
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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.

• Korean Journal of Environment and Ecology
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• v.34 no.3
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• pp.191-197
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• 2020

The purpose of this was to examine the differences of large whopper swan (Cygnus cygnus) in wintering habitat preference among bridge sections of the lower Nakdong River of the Nakdong River Estuary, the largest whopper swan's wintering habitat in Korea. This species is designated and protected as Natural Monument in Korea. The survey was conducted in six time-series during the 2018~2019 wintering season, and it found up to 500 whopper swans were wintering in the lower Nakdong River. For the survey, a seven sections were set up based on the bridges across the river. Whopper swans were rarely observed in five narrow sections where the distance between bridges was less than 2 km. The stable population of the whopper swan was observed only in two broader sections where the distance between bridges was is over 4 km. As these sections were relatively little affected by artificial interference, the distance from the mouth of the Nakdong River was not a factor. Securing a stable space is considered as one of the most important factors for wintering of whopper swans, which are an endangered species. The survey results indicate that the distance between bridges should be at least 4 km to secure the whopper swan's stable habitat. These results are expected to be a reference to the development or restoration of the river ecosystems, especially bridge construction.

• ALGAE
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• v.17 no.3
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• pp.171-185
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• 2002

The standing crop of genus Microcystis, microcystin concentrations and environmental factors were monitored at stations of the lower reaches of the Nakdong River in 1998 and 1999 during the periods of its occurrence. The Microcystis were observed from May to Octorber, and the cell density was highest at Station Seonam up to 250,000 cells${\cdot}ml^{-1}$ forming scum over the water surface. There were signigicant relationships between the standing crop of Microcystis and nitrate nitrogen, total phosphorus concentrations and Ph. Presumably these parameters were important in the succession to Microcystis dominated phytoplankton community in the summer period in the river. However, Ammonium nitrogen, phosphate phosphorus concentrations and N/P ratio were not critical factors. The Microcystis bloom was notable above $25^{\circ}C$ of surface water temperature. Microcystins were detected from May to November in the algal materials from the river. The 84.2% of algal materials with Microcystis exhibited the microcystin with the maximum of 1711.8 ${\mu}g{\cdot}g^{-1}$ dw. The microcystin concentrations in the algal materials were significantly related to the stading crop of Microcystis, which was the primary determinant factor in the toxin levle of algal materials. The concentrations were also significantly related to pH of the water column in the positive pattern.

• Journal of Fisheries and Marine Sciences Education
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• v.24 no.6
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• pp.920-933
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• 2012

Marine algal flora and community structure were investigated seasonally at four stations in Busan, in which coastal area and estuary affected by Nakdong river are involved, from February 2011 to October 2011. Total 78 species including 9 of cholophyta, 17 of phaeophyta and 52 of rhodophyta were found during the study period. Maximum and minimum species number were recorded at station 1(57 species) and at 3(32 species). As based on the cluster analysis, grouping pattern between the four stations was significantly affected by season and Nakdong river run off. At station 3 directly exposured on Nakdong river run off, species diversity was relatively low and dominant species were similar throughout four seasons. However, coverage at the station was relatively high because of Ulva bloom. This difference results from salinity and nitrates concentrations closely related with river runoff controlled according to precipitation. Marine algal coverage was high at lower salinity and higher nitrate concentration. In conclusion, the spatio-temporal distribution of benthic marine algae in estuary of Nakdong river was mainly determined by the precipitation and river run off with the seasons, whereas that in coastal area was seasonally affected by general physical, chemical, biological and dynamic factors.

• Membrane and Water Treatment
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• v.13 no.5
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• pp.245-257
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• 2022

Water quality characteristics and their spatial variations in the Nakdong River were statistically analyzed by multivariate techniques including correlation analysis, CA, and FA/PCA based on water quality parameters for 17 sites over 2017-2019, yielding PI values for primary factors. Site 10 indicated the highest parameter concentrations, and results of pearson's correlation analysis suggest that non-biodegradable organic matter had been distributed on the site. Five clusters were identified in order of descending pollution levels: I (Ib > Ia) > II (IIa > IIb) > III. Spatial variations started from sub-cluster Ib in which Daegu city and Geumho-river are joined. T-P, PO4-P, SS, COD, and TOC corresponded to VF 1 and 2, which were found to be principal components with strong influence on water quality. Sub-cluster Ib was strongly influenced by NO3-N and T-N compared to other clusters. According to the PIs, water quality pollution deteriorated due to non-biodegradable organic matter, nitrogen- and phosphorus-based nutrient salts in the middle and lower reaches, illustrating worsening water pollution due to inflows of anthropogenic sources on the Geumho-river, i.e., sewage and wastewater, discharged from Site 10, at which there is a concentration of urban, agricultural, and industrial areas.

• Journal of Environmental Science International
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• v.32 no.8
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• pp.533-542
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• 2023

Understanding the regional distribution of swans in the lower Nakdong River area is also important for the continuous habitat of swans according to changes in the surrounding environment of the area. This study was conducted to understand the regional distribution aspect of swans (Cygnus spp.) downstream of the Nakdong River, Republic of Korea, from October 2013 to September 2018. In the estuary, a small ship was used to move along a certain route and observe it with the naked eye or binoculars, and in the land area, Line transect census and Point census method were conducted in parallel. During this period, two species and 34,647 individuals of swans were observed, including 34,356 Whooper Swans (Cygnus cygnus) and 291 Tundra Swans (Cygnus columbianus). The average number of individuals observed in 15 different areas was 1172, 103, 214, 1825, 1850, 13, 318, 1, 0, 1, 11, 21, 5, 0, and 239 respectively. The total average of the number of individuals in these areas was 384.76. The numbers differed significantly among the survey areas (Kruskal-Wallis test, X2=4349.01, P < 0.001). Particularly, the numbers were larger in Eulsukdo, Lower Eulsukdo, and Daemadeung than in the other regions. In conclusion, as long-term survey data, it can be used as basic data to analyze the distribution of swans due to environmental changes caused by the development of the Nakdong River, predict changes in the habitat status of migratory birds, and prepare measures necessary for preservation.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.445-452
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• 2020

Tributary is a part of life space for people and a very important place that accommodates rest recreation and other daily activities. absolutely insufficient basic data about water quality and flow rate are available for basin management. Efficient water and basin management systems, which are also supported by local residents can be established by securing such basic data of major tributaries in the Nakdong river system. In this study, the fluctuation characteristics of upstream and downstream water pollution levels were compared using the measurement results of the water environment measurement network and the tributary monitoring project for the gyeseong-stream and Hwapo-stream in the Nakdong-miryang watershed. In 2017, when water pollution is the highest, it was confirmed that the annual average rainfall was the lowest. Although the upstream and downstream water quality tendencies of the Gyeseong-stream are similar, the water quality concentrations of the Gyeseong-stream are relatively different. But although the Hwapo stream has various causes of pollution, there was not much difference in the level of pollution between the upper and lower streams. In addition, both rivers need the ability to purify rivers by securing sufficient water for river maintenance, and if the correlation between water quality items can be inferred through continuous monitoring of tributaries where the aspect of water quality change is unclear, water quality management Determined to be efficient operation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.2
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• pp.55-63
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• 1980

To study run-off characteristics in the small watersheds in Korea, investigations had been carried out for a period of 4 years from 1972 to 1975 in the sample watersheds. The samples were selected in four major river basins such as the Han River, the Keum River, the Nakdong River and the Yongsan River. Water levels and rainfall data had been. collected from each sample area where the measuring instruments were installed. The findings of this investigation can be summarized as follows; 1. With an average runoff rate of 60% in the sample watersheds, the average runoff rate. in each sample proved to be as below; the Han River Basin : 41.4% the Keum River Basin : 61.7% the Nakdong River Basin : 69.4% the Yong San River Basin : 69.2% 2. The base flow rate in the sample watersheds proved to be 8.1 mm/month. 3. A comparison of the runoff obtained from actual measurements made and that calculated by the Kaijyama formula showed that the latter is 9.1% lower than the former.

• ALGAE
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• v.20 no.2
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• pp.133-140
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• 2005

Daily variation of phytoplankton community and environmental parameters were investigated at the lower Nakdong River (Mulgum) from January 2002 to December 2003 to investigate the dynamics of a phytoplankton community in detail. The daily results of water quality in this investigation showed pH (8.1 $\pm$ 0.7), DO (10.3 $\pm$ 2.7 $mg{\cdot}l^{-1}$), water temp. (18.8 $\pm$ 7.4°C), BOD (2.4 $\pm$ 1.0 $mg{\cdot}l^{-1}$), COD (5.3 $\pm$ 1.2 $mg{\cdot}l^{-1}$) and chl. a (43.5 $\pm$ 35.1 mg ${\cdot}m^{-3}$). The results of nutrient factors were the following: TN (3.1 $\pm$ 0.8 $mg{\cdot}l^{-1}$), NO3-N (2.5 $\pm$ 0.5 $mg{\cdot}l^{-1}$), TP (90 $\pm$ 48 ${\mu}g\;{\cdot}\;l^{-1}$), PO4-P (43 $\pm$ 30 ${\mu}g\;{\cdot}\;l^{-1}$). Dominant phytoplankton species during the study period were diatom (Stephanodiscus hantzschii, Aulacoseira granulata var. angustissima and A. italica) and cyanobacteria (Microcystis aeruginosa, Aphanizomenon flos-aquae). The small centric diatom, Stephanodiscus hantzschii, was repeatedly dominant from late fall to the following spring (mean and maximum cell density, 2.3 × 103 $\pm$ 3.8 × 103, 4.5 × 105 cells $ml^{-1}$, respectively). Pinnate diatom, Aulacoseira granulata var. angustissima and A. italica, were frequently observed all season except January to March. Cyanobacteria, Microcystis aeruginosa and Aphanizomenon flos-aquae, proliferated in summer of 2002 except in 2003 due to heavy precipitation. The dominant zooplankton species (March-early May) was rotifer (Brachionus, Keratella, Polyarthra) and cladocerans (Diaphanosoma). The daily observed dynamics of the phytoplankton community in the lower Nakdong River in this study may play an important role in increasing the detailed resolution of limnological information and serving as ecological data for future studies.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4B
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• pp.405-411
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• 2008

The Nakdong River Estuary Barrage (NREB) was constructed in 1987 to prevent saltwater intrusion and to provide the sustainable water supply in the upstream channel. Sediment dredging has been conducted to eliminate deposited sediments in the approached upstream channel of the NREB. Fluvial changes and sedimentation problems have been continued due to urbanization and development in the watershed as well as construction of the NREB. However, the sufficient field monitoring and researches for sedimentation characteristics and bed changes have not been performed after construction of the NREB. Therefore, bed elevation changes and seasonal sediment concentration distribution were analyzed using the quasi-steady state model with historical field data in this study. The water surface elevation changes with and without sediment dredging operation were calculated using the developed quasi-steady state model and finally the sediment dredging effects were evaluated.