• Journal of Wetlands Research
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• v.16 no.4
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• pp.389-402
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• 2014

In this study, simulation technique with multi-dimensional model(EFDC), coupled with COSFIM and FLDWAV, has been applied to the upstream and downstream of weirs for hydraulic characteristics analysis through development of system and was performed for 8 multi-function weirs on Nakdong river using developed system. COSFIM, FLDWAV and EFDC can utilize suitable model in situation because they have pros and cons according to practical use purpose. Developed technique can offers spatial and grid unit information as well as line and section unit information from 1-D modeling. It is considered that the coupling simulation technique can provide useful hydraulic information for river management and treatment.

• Journal of Environmental Science International
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• v.10 no.2
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• pp.105-111
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• 2001

Improvement of water quality and Investigation of bacterial characteristics have been conducted in a pilot plant using biological activated carbon (BAC) in water treatment process at the downstream of the Nakdong River. Most of water control parameters were highly improved after passing through BAC. Approximately 54% of dissolved organic carbon was removed in coal-based BAC process. Bacterial biomass and bacterial production appeared $9.8{\times}10^8 CFU/g and 7.1mg-C/m^3$.hr in coal-based BAC, respectively. Predominant bacteria species grown in BAC were identified as Pseudomonas, Flavobacterium, Alcaligenes, Acinetobacter and Aeromonas species. Particularly Pseudomonas vesicularis was dominant in both coal-based and coconut-based BACs, while Pseudomonas cepacia was dominant in wood-based BAC.

• Ecology and Resilient Infrastructure
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• v.7 no.4
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• pp.353-365
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• 2020

In this study, the characteristics of bed elevation changes of the Nakdong River when weir gates are opened were analyzed using the Hydrologic Engineering Center-River Analysis System (HEC-RAS). The study area was 292.37 km downstream of the Gudam Bridge to the Nakdong estuary of the Nakdong River. The HEC-RAS program, which is a 1D numerical analysis model, was used to simulate bed elevation changes. Simulations were conducted under two scenarios from 2017 to 2019. Scenarios 1 and 2 were devised under the conditions of a fully opened gate and during gate installation, respectively. Results confirmed that, under the conditions of Scenario 1, deposition occurred in most sections from the Hapcheon-Changnyeong weir to the Changnyeong-Haman weir (a distance of approximately 40 km). In addition, it was predicted that the flow that included sediments in the main stream of the Nakdong River was not interrupted by the weir structure and regularly produced changes in the river bed.

• Journal of Environmental Science International
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• v.24 no.11
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• pp.1417-1430
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• 2015

In this study we were to explore the seasonal variation of water temperature distributions before and after weir construction at Gumi, Chilgok, Gangjung(Goryung), Dalsung in the Nakdong River using Landsat satellite images. Relationship between in-situ water temperature and radiance values of Landsat-5, 7, 8 satellite images showed high correlation. Seasonal variation of water temperature in Nakdong River showed that the fluctuation ranges of water temperature before weir construction were larger than those after weir construction. This indicated that the variation of water temperature is due to the difference of heat storage volume by weir construction and dredging work. In particular, the water temperature after weirs construction in autumn was 4-8 times lower than that before weirs construction. Water temperature after weir construction decreased in spring and summer at the downstream of Gumi weir and Gangjung(Goryung) weir, and the upstream of Dalsung weir. In autumn and winter, the water temperature after weir construction increased in the upstream and downstream of the whole weirs except upstream of Gumi weir. Relationship between water temperature and meteorological elements (air temperature, wind speed, sunshine, radiation) showed high correlation of above 94% in air temperature, and then radiation was high correlation before and after 65%.

• Journal of Korean Society on Water Environment
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• v.39 no.6
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• pp.451-464
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• 2023

Harmful cyanobacterial monitoring is time-consuming and requires skilled professionals. Recently, Phycocyanin, the accessory pigment unique to freshwater cyanobacteria, has been proposed as an indicator for the presence of cyanobacteria, with the advantage of rapid and simple measurement. The purpose of this research was to evaluate the correlation between the harmful cyanobacterial cell density and the concentration of phycocyanin and to consider how to use the real-time water quality monitoring system for algae bloom monitoring. In the downstream of the Nakdong River, Microcystis spp. showed maximum cell density (99 %) in harmful cyanobacteria (four target genera). A strong correlation between phycocyanin(measured in the laboratory) concentrations and harmful cyanobacterial cell density was observed (r = 0.90, p < 0.001), while a weaker relationship (r = 0.65, p < 0.001) resulted between chlorophyll a concentration and harmful cyanobacterial cell density. As a result of comparing the phycocyanin concentration (measured in submersible fluorescence sensor) and harmful cyanobacterial cell density, the error range increased as the number of cyanobacteria cells increased. Before opening the estuary bank, the diurnal variations of phycocyanin concentrations did not mix by depth, and in the case of the surface layer, a pattern of increase and decrease over time was shown. This study is the result of analysis when Microcystis spp. is dominant in downstream of Nakdong River in summer, therefore the correlation between the harmful cyanobacteria density and phycocyanin concentrations should be more generalized through spatio-temporal expansion.

• Journal of Korea Water Resources Association
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• v.56 no.spc1
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• pp.1015-1026
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• 2023

The confluence of rivers, where rivers meet, is a place known for complex water mixing dynamics. Sometimes, these rivers flow downstream without mixing. While this non-mixing can pose challenges for water quality management, it also offers the potential for improved water extraction in nearby water intakes (Chilseo). In this study, we analyzed the mixing dynamics at the confluence of the Nakdong River and the Nam River using drone imagery, water quality indicators like Electrical Conductivity, and hydraulic factor Secondary Flow. We found that meandering effects hindered mixing, as shown by the comparison of Secondary Flow and Electrical Conductivity distributions. Additionally, the Chilseo Water Purification Plant downstream of the Nakdong River-Nam River confluence extracted unmixed Nam River water during certain periods.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.5
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• pp.64-73
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• 1996

When typhoon occurs, the meteorological conditions get worse and can cause a large damage from storm and flood . This damage, however, can be minimized if a precise analysis of the runoff characteristics by typhoon tracks is used in the flood contorl This paper aims at the analysis of storm occurrence and runoff characteristics by typhoon tracks in Nakdong river basin. Therefore, the data of 14 typhoons which invaded Nakdong river basin during the period from 1975 to 1991 were collected, analyzed, and studied. The major results of this study are as followings; 1) The frequency of the typhoon occurrence here in Korea was affected by the storms three times a year on the average. The highest-recorded frequency was during the months of July to September. 2) The survey of the track characteristics depending on the forms of the storm in the Nakdong river basin showed that typhoon storm advanced from the south of the basin to the north, while the frontal type storm was most likely to advanced from the west to the north. 3) Typhoon tracks are classified into three categories, 6 predictors with high correlation coefficient are finally selected, and stepwise multiple regression method are used to establish typhoon strom forecasting models. 4) The riview on the directions of progress of the storm made it clear that the storm moving downstream from upstream of the basin could develop into peak discharge for ca short time and lead to more flood damage than in any other direction.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.197-207
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• 2015

Modification of travel time is necessary in all Nakdong river basin because hydrological conditions of Nakdong river basin were changed after major rivers project. Also calculation of flood travel time at between sections of weirs is necessary. In this study, flood travel time was calculated using hydraulic model and the latest topographical data from Changnyeong-Haman weir to Nakdong river estuary bank. Analysis of discharge and stage conditions were carried out. 84 of the scenarios were organized according to flow rate, discharge type, boundary conditions, and tributary conditions. Flood travel time of initial and peak were calculated with discharge and stage conditions, respectively. The results of this study will be available in practical business work such as flood forecast warning and weir operation on algae removal.

• Journal of Environmental Science International
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• v.19 no.10
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• pp.1219-1227
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• 2010

In this study, the sensitivity analysis of bed changes due to the various sediment transport equations have been conducted for 80 km reach of the Lower Nakdong River using the HEC-6 which is one dimensional numerical model. The bed elevation changes according to the different sediment transport formulas were compared and analyzed quantitatively. As a result of the numerical simulation, the final bed elevation calculated by Engelund and Hansen(1967), Ackers and White(1973), and Yang(1979) formulas was similar to one another in configuration. The bed change simulated by Engelund and Hansen(1967) were greatest among them, for example, 5.5 m deposition and 2.9 m erosion for 100 years. Also, in the case of Toffaleti (1969) equation, the maximum bed deposition of 8.04 m after 100 years was induced at the 73 km location upstream of the Nakdong River Estuary Barrage. Meyer-Peter-M$\ddot{u}$ller(1948) and Wilcock(2001) formulas produced the deposition only at the upstream end and there was little bed change in the downstream area. The unreal bed configuration of continuously up and down pattern was simulated by Laursen(1958) transport equation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.3
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• pp.561-573
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• 2017

Nakdong River was recently dredged with multi-functional weirs construction. Therefore, the depth was deepened and the lag time also increased. As a result, stratification occurred in some sections with deep water depth, and it also caused the increase of algal bloom phenomenon. The purpose of this study is to evaluate reproducibility of stratification in the Nakdong River by applying the EFDC model, which is a three-dimensional hydraulic and water quality analysis model proving the reproducibility of stratification phenomena in reservoirs and estuaries. In order to reproduce the Nakdong river water temperature and DO stratification, EFDC model was constructed in the downstream part of the Nakdong river and sensitivity analysis was performed on key parameters sensitive to stratification. Sensitivity analysis was used to reproduce stratification by selecting optimal parameters. The results of this study can be used as basic data for the analysis of various destratification scenarios.