• Journal of the Korean earth science society
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• 제34권6호
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• pp.561-574
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• 2013

This study investigates energy fluxes measured near Gangjeong-Goryeong Weir of the Nakdong River of South Korea for more than a year, from July 2011 to September 2012, in order to analyze the applicability of the data for future impact analyses. Each of the two study sites is located in a rural area, surrounded by agricultural fields, and an urban industrial area. Sensible and latent heat fluxes are analyzed according to the wind direction. In the summertime, when the wind blows from the river, sensible heat tends to decrease and latent heat tends to increase at both sites. This result is considered to be caused by moisture transfer from the river. Bowen ratio, energy balance closure, momentum flux, and stability are analyzed as well. The Bowen ratio of the rural agricultural site turns out higher than that of the urban site regardless of the season. The energy balance closure is higher at the agricultural site compared to the urban area, which is mainly due to exclusion of the storage term calculation at the urban site. The momentum flux is greater at the urban site both in winter and summer. The instability lasts longer during daytime and in the summertime, when there is a strong turbulence. The data from these sites are appropriate to be used in analyzing the impact of river in surrounding areas for future studies.

• Journal of Environmental Science International
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• 제27권7호
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• pp.477-488
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• 2018

In this study, heavy metal levels at the sediment monitoring network site upstream of the Gangjeong-Goryeong weir in the Nakdong River were surveyed from 2012 to 2016. We assessed the sediment pollution level using various pollution indexes based on ICP-MS analysis. The stream sediment pollution assessment standard, established through Regulation No. 687 of the National Institute of Environmental Research (2015), pollution load index (PLI), potential ecological risk index (RI), and mean PEL Quotient (mPELQ) were used to evaluate the sediment pollution level. We verified the representativeness of the monitoring point through the distribution of sedimentation and scour behavior by river bed surveying using anacousticDopplercurrentprofiler.

• Journal of Wetlands Research
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• 제19권2호
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• pp.181-192
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• 2017

Analysis using a numerical model is important to understand the sediment transport mechanism associated with erosion and sedimentation near weirs and other hydraulic structures within riverine systems. The local riverbed change near a hydraulic structure (Gangjeong-Goryong multi-function weir in the Nakdong river) was analyzed in order to examine the effect of hydraulic structures on local bed change. A 2D numerical model (CCHE-2D) was employed to simulate the sedimentation and erosion over a reach (25 km) including the weir. For the calibration and verification of the model, rainfall data from a real event (Typoon 'Ewiniar' in 2006) were used for flow and stage simulation. And the simulated results show a good agreement with the observed data for the whole domain. From the result, it was found that the installation and operation of the weir could aggravate bed changes by typhoon between movable weirs, and which resulted in redistribution of sediment.

• Journal of Environmental Impact Assessment
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• 제24권3호
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• pp.278-286
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• 2015

Pilot scale system was designed to identify the growth and movement of algae, depending on environmental changes(retention time, nutrient concentration, etc) in Gangjeong-Goryeong Weir of the Nakdong River. Considering the stability of algal culture and easy observation of algal growth, pilot scale system was made of transparent acrylic material(3 sets of flexible cylindrical water tanks with 1 m diameter and 4 m height). Auxiliary equipments include light intercepter, water inflow device for different water depth and storage of reclaimed water. The retention time was 2 days(before construction of weir; treatment 1), 8 days(after construction of weir, 2013; treatment 2) and 30 days(2014; treatment 3). According to the water temperature of treatment 1 were similar by depth, treatment 3 showed a difference between the surface(0 m) and bottom(4 m) more than $3^{\circ}C$. DO, pH showed relatively high in the surface than the bottom. Nutrients showed eutrophic condition in all experiments. The Chlrophyll-a concentration of the treatment 1 showed a relatively lower value than the Chlrophyll-a concentration of the treatment 2 and 3. Therefore, the retention time was considered to influence the growth of phytoplankton.

• Journal of Korea Water Resources Association
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• 제48권9호
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• pp.743-756
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• 2015

It is necessary to evaluate the effect of dredging and weir operation on the flow and long-term bed change for river management. Especially, large scale river treatment project, with dredging or weir installation and operation, can increase the instability of riverbed in tributaries as well as mainstream. This study focuses on the effect of weir installation and dredging on the long-term bed change in Nakdong river (Gangjeong- Goryeong Weir~Dalseong Weir) and its tributary (Geumho river). HEC-6 model has been used to analyze the amount of long-term bed change and sediment transport resulted from the river treatment including dredging or weir installation. From the result, it was concluded that a large scale river treatment can accelerate and increase the long-term bed change both in mainstream and tributary.

• Korean Journal of Ecology and Environment
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• 제56권4호
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• pp.348-362
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• 2023

This study analyzed the monitoring results of fishways at 16 weirs constructed on four large Rivers to provide data helpful for the operation and management of fishways. The average utilization rate of the fishways at the weirs was confirmed to be 64.9%. When comparing the dominant species in the mainstream and fishway monitoring results, differences were observed in 9 weirs (56.3%). This indicated that the species prevalent in the mainstream were not necessarily the ones most frequently using the fishways. The average number of individuals using the fishways per day was 336. When classifying the fish species using the fishway by life type, 92.3% were primary freshwater fish, and migratory species accounted for only 5.6%. Analysis based on the season of fishway usage revealed that an average or higher number of fish species used the fishways from May to October, with the highest number of individual users occurring from June to August. Between May and July, 80% of the fish species using the fishways were in their spawning period, while during other season, less than 40% were species that move during the spawning period. The fishways that showed a significant alignment between the spawning period and the fishway passage period were Rhinogobius brunneus, Leiocassis nitidus, Squalidus chankaensis tsuchigae, Pseudogobio esocinus, Acheilognathus rhombeus, and Pungtungia herzi, in that order. When comparing the fishway monitoring results of the Gangjeong-Goryeong Weir and the Dalseong Weir with the upper part water level of the weir, both the number of fish species and individuals using the fishway showed positive correlations with the upper part water level of the weir. This suggests that a higher water level of the weir increases the inflow discharge within the fishway, leading to increased use by fish (number of individuals in Gangjeong-Goryeong Weir, P<0.001; number of species in Dalseong Weir, P<0.05). This study summarized and analyzed the results of fishway monitoring at 16 weirs built on four large Rivers, considering fishway efficiency, operation and management, monitoring period, and regulation of water level in the upper part of the weir. It is thought that this will help understand the status of fish use in fishways on large River and aid the construction, operation, and management of fishways in the future.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2015년도 학술발표회
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• pp.369-373
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• 2015

본 연구에서는 낙동강 강정고령보에서 달성보 구간에 대한 지속적 지형조사를 통해 다기능보 건설 및 운영으로 인한 하천지형의 변화양상과 정도를 파악하고자 하였다. 이를 위하여 4대강살리기사업 이전의 측량성과(낙동강하천기본계획, 2009년)를 기준으로 보 건설 및 하도정비 이후인 2013년과 2015년에 실측한 지형자료와 비교하였다. 2013년과 2015년 지형자료 취득은 대상구간(강정고령보~달성보: 23 km) 내 하도와 홍수터에 대해 각각 단일 및 다중빔 음향측심기와RTK-GPS 등의 측량장비를 이용하여 40 m 이상의 평면공간해상도를 가지도록 수행하였다. 대상구간 내 하천기본계획 지정 횡단측선에 대해 2013년과 2015년 지형정보를 비교함으로써 보 건설 및 하도정비로 인한 지형변화양상과 정도를 파악하고자 하였다. 특정 측선에서의 횡단지형자료인 2009년 측량성과와 비교하여 2013년과 2015년 실측자료는 전체 대상구간에 대한 3차원 공간정보를 제공함으로써 이들 간의 정성, 정량적 비교를 통하여 보 건설 및 운영을 통한 하도내 국부적 지형변화의 정도와 양상을 파악할 수 있었다. 이를 통해 하천의 지형학적, 수리학적 특성뿐만 아니라 보 건설 및 하도정비 등의 물리적 여건변화에 따른 특정 하천구간에 대한 시 공간적 지형변화특성을 파악할 수 있었으며, 이는 향후 하천관리 및 설계를 위한 연구와 실무에 널리 활용될 수 있을 것으로 기대된다.

• Korean Journal of Ecology and Environment
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• 제53권1호
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• pp.55-62
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• 2020

Chironomidae widely utilize as a biological indicator that has various types of feeding pattern such as omnivorous, herbivorous and carnivorous. Polypedilum scalaenum is known as omnivorous, it plays an important role in the food chain of freshwater ecosystems in Korea. Nevertheless, detailed information about diet items of P. scalaenum is still lacking. The purpose of this study is to identify the gut and intestine contents of items on P. scalaenum inhabiting the large-scale weirs of the four major river ecosystems(Ipoh Weir, Sejong Weir, Juksan Weir, Gangjeong-Goryeong Weir, and Dalseong Weir). Phytoplankton was dominant diet items among the study sites. However, zooplankton (i.e. appendages, setae) only found in Ipoh Weir. The phytoplankton species composition in the study sites was correspond to the diet items in the gut and intestine contents of P. scalaenum. In summary, analysis of P. scalaenum gut and intestine contents in this study was able to identify the feeding characteristics of omnivorous Chironomidae, and in particular, it was possible to study the species composition of basic producers in the surrounding aquatic environment by analyzing the contents of the digestive tracts.

• Journal of Environmental Science International
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• 제24권5호
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• pp.657-670
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• 2015

Visibility and Automatic Weather System(AWS) data near Nakdong river were analyzed to characterize fog formation during 2012-2013. The temperature was lower than its nearby city - Daegu, whereas the humidity was higher than the city. 157 fog events were observed in total during the 2 year period. About 65% of the events occurred in fall (September, October, and November) followed by winter, summer, and spring. 94 early morning fog events of longer than 30 minutes occurred when south westerly wind speed was lower than 2 m/s. During these events, the water temperature was highest followed by soil surface and air temperatures due to the advection of cold and humid air from nearby hill. The observed fog events were categorized using a fog-type classification algorithm, which used surface cooling, wind speed threshold, rate of change of air temperature and dew point temperature. As a result, frontal fog observed 6 times, radiation 4, advection 13, and evaporation 66. The evaporation fog in the study area lasted longer than other reports. It is due to the interactions of cold air drainage flow and warm surface in addition to the evaporation from the water surface. In particular, more than 60% of the evaporation fog events were accompanied with cold air flows over the wet and warm surface. Therefore, it is needed for the identification of the inland fog mechanism to evaluate the impacts of nearby topography and land cover as well as water body.

• Journal of Environmental Science International
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• 제27권6호
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• pp.371-381
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• 2018

Multifunctional weirs constructed through the Four Major Rivers Restoration Project are operated as management water levels. The purpose of this study was to evaluate the effect of water level in the main stem on the tributary water level according to multifunctional weir operation, because the operation of multifunctional weirs for water level management influences the drainage of tributaries. In this study, water level pressure gauges were installed and spatial and temporal water quality was observed. The LOcally Weighted Scatterplot Smoothing (LOWESS) technique was applied to the Nakdong River and the Baekcheon Junction, both upstream of the Gangjeong-Goryeong weir, in order to analyze water quality trends. When considering the overall analysis and observations, it was found that the water quality forecasting point located at the Baekcheon estuary point should be transferred to the Dosung Bridge, which is located upstream of the Sunwon Bridge.