• Journal of Ocean Engineering and Technology
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• v.32 no.3
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• pp.192-201
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• 2018

In this study, a qualitative evaluation of the morphological changes in the seabed surrounding Jinwoo-Island due to the construction of the new Busan port were determined through a numerical simulation. Various scenarios for the discharge of the Nakdong river estuary dam and construction stage of the new Busan port were established and utilized for an indirect and qualitative investigation through simulation using the numerical model implemented in this study. It was concluded through a qualitative study that the morphological changes in the seabed surrounding Jinwoo-Island were typical estuary seabed changes due to the discharge of the Nakdong river estuary dam and waves from the open sea. The effects from the construction of the new Busan port were relatively small.

• Proceedings of the Korea Society of Environmental Biology Conference
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• 2001.12a
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• pp.131-131
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• 2001

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.1
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• pp.11-20
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• 2006

The Nakdong Estuary is complex water system, where sea water and fresh water meet each other. It has undergone the significant change of its environmental conditions since the construction of the Nakdong River Barrier in 1987. Prior to its construction, mixing and circulation processes in the Nakdong Estuary was dominated by tidal current. However, after the dam construction, those processes were greatly altered by the artificial control of the fresh river water discharge. In this paper, the influence of opening and closing the floodgate of Nakdong River on the outflow behavior of estuarine water from the Nakdong Estuary is analyzed in detail.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.1
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• pp.1-11
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• 2017

Nakdong River Estuary is affected by the dam, barrage construction and dredge and reclaim worked artificially. So, we have studied the area input both freshwater and sea water to understand marine environment of Nakdong River estuary related to the effect of artificial work from 2013 to 2015. As a result, The discharge flow to the estuary remarkably decreased before barrage construction and the average of salinity at the estuary increased. So, the brackish water zone reduced under the influence of decreased discharge flow. The major sources of nitrate and silicate were freshwater, phosphate supplied from bottom and the open sea water. The concentration of phosphate and dissolved oxygen (DO) decreased remarkably in spring and summer. we investigated that phosphate in freshwater was removed under the influence of the estuary dam and phosphate in sea water was removed under the influence of phytoplankton. The low concentration of DO was due to decomposition of the organic compound by microorganism after phytoplankton blooms. Generally, the concentrations of chlorophyll-a in summer was higher than spring and fall. Therefore, the change of ecosystem in Nakdong river estuary was due to decrease of freshwater influx, the other change is facing because of the barrage.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.3
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• pp.91-102
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• 2016

The spatio-temporal variations of the dissolved methane concentration were investigated and the methane budget was estimated in the Nakdong Estuary in January, September, and November of 2014. Dissolved methane showed seasonal variation (21~874 nM) with high concentration in summer due to enhanced temperature and fresh water discharge. Decreasing trends of dissolved methane from the river to the estuary were consistent in all seasons showing the main source of the estuarine methane is river discharge. However, the decreasing trends were modified seasonally due to the local sources such as organic-rich sediments in intertidal zone or near the estuarine barrage. Dissolved methane concentration in the Nakdong Estuary was high, compared to other estuaries probably due to the well developed wetland in Nakdong-river system and stagnation effect from barrages and dams. Dominant sink for the Nakdong estuarine methane was outflux into the atmosphere. Relatively long residence time (produced by barrier island and estuarine dam) in the estuary might provide the enough time for the outgassing.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.78-85
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• 2008

We estimated the pollutant loads for the last 3 years based on the daily discharge at the Nakdong River dam(barrage) and spatiotemporal characteristics of seawater quality in the Nakdong river estuary to investigate the correlation between the pollutant load inflow rate and seawater quality. The main results from this research are summarized as follows. (1) The total discharge at the Nakdong River dam dam the last 11 years has been $224,576.8{\times}10^6m^3/day$. The discharge figures show that the maximum discharge occurs in August with $52,634.2{\times}10^6 m^3/day$ (23.4% of the year's volume), followed by July and Sep. in that order with 23.1 and 17%, respectively. (2) The pollutant load influx from the Nakdong River dam was composed of 307,591.3COD-kg/day, 128.746.1 TN-kg/day, and 107,625.8 TP-kg/day. (3) The surface temperature in the Nakdong River estuary was about $2.137^{\circ}C$ higher than that of the lower layer. The salinity of the lower layer was 2.209%o higher than that of the ocean surface. The salinity of the ocean surface decreased by up to 19.593%o due to the inflow of the discharge at the Nakdong River dam. (4) DO, COD, TN, and SS concentration levels tended to be higher at the ocean surface than in lower layers, whereas the reverse was true for TP. (5) The water mass at the ocean's surface and in the lower layers during the drought and flood seasons tended to be separated by the difference in densities due to the freshwater inflow.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.251-258
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• 2001

The ichthyofauna and passing efficiency of fish ways were surveyed in the lower and upper regions of the river mouth dam in the lower reaches of the Nakdong river from June to December in 20()0. As the dam built in the river mouth, the brackish area in the estuary disappeared completely and the transitional area did not formed. The fishes collected from survey were classified into 49 species, 45 genera belonging to 29 families. Among them, the fresh water fishes composed of 10 species, peripheral freshwater fishes 11 species and sea water fishes 28 species respectively. Because of the ecological difference between the fresh and sea water, dominant species in the Myeong-ji of sea water area was Acanthogobius flavimanus (39.1%) and in the Sa-sang of fresh water area was Achanthorhodeus macropterus (44.4%). By the video camera records, fishes were identified nine species like as Coilia ectenes, Cyprinus carpio, Hemibarbus labeo, Squalidus gracilis majimae, Plecoglosus altivelis, Lateolabrax japonicus, Anguilla japonica, Mugil cephalus and Pholis nebulosa. Based on total species collected, the efficiency of the fish way for the anadromous fish was 10.1%. Therefore, efficiency evaluation of the fish way in the Nakdong River Mouth Dam was low.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.1
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• pp.59-69
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• 2013

Temporal and spatial variation in the freshwater region, created by river runoff, of a small bay, caused by the passage of typhoons was examined using a three-dimensional primitive equation model (the Princeton Ocean Model, POM). Numerical experiments were implemented focusing on temporal evolution in the freshwater region in association with typhoon tracks. The model domain covered most of the estuary around the Nakdong River, including Noksan Bay, where river water is periodically released from upstream (Noksan dam). The model showed that the extension of the freshwater region outside of the bay depended strongly on the tracks of typhoons, specifically the associated wind directions and inner flow fields that are accompanied by new clockwise eddies. The model also showed that entrainment from typhoon passage frequently creates salt wedges in the estuary, indicating that organisms in the bay are biologically and chemically influenced with variation in the freshwater region.

• 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.

• Journal of Korea Water Resources Association
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• v.44 no.7
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• pp.577-590
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• 2011

In this study, the watershed and water body models were linked for the simulation of the Nakding river flow. This is a pre-step study for the estimation of the effect of the flow and water quality on the climate change. For models of watershed and river flow, the SWAT and EFDC were used, respectively. The runoff discharge at each boundary points for the simulation of the river flow was provided from the drainage basin model. The calculated runoff discharge by the SWAT model was compared with the measured data of the Ministry of Environment at 13 locations along the Nakdong river and 30 locations along the tributary streams. The computed water discharge was shown to be similar with the measured data. For the model calibration and verification, % difference, NSE, and $R^2$ were computed. The computed % difference was within 15% except of a few points. The NSE and $R^2$ were also within a fair level. The Nakdong river flow of 2007 was simulated by using the EFDC model. The comparison with the measured data showed that the model reflected the actual values of low and high flow well. Also, it was confirmed that the acceleration and deceleration in the curved areas were appropriately simulated. The movement of dye injected at the upstream boundary was simulated. The result showed that the arrival time up to the estuary dam was computed to be about 65 days.