• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.343-353
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• 2013

Flow duration curve (FDC) can be developed by linking the daily flow data of stream flow monitoring network to 8-day interval flow data of the unit watersheds for the management of Total Maximum Daily Loads. This study investigated the applicable method for the development of long term FDC with the selection of the stream flow reference sites, and suggested the development of the FDC in 4 river basins. Out of 142 unit watersheds in 4 river basins, 107 unit watersheds were shown to estimate daily flow data for the unit watersheds from 2006 to 2010. Short term FDC could be developed in 64 unit watersheds (45%) and long term FDC in 43 unit watersheds (30%), while other 35 unit watersheds (25%) were revealed to have difficulties in the development of FDC itself. Limits in the development of the long term FDC includes no stream monitoring sites in certain unit watersheds, short duration of stream flow data set and missing data by abnormal water level measurements on the stream flow monitoring sites. To improve these limits, it is necessary to install new monitoring sites in the required areas, to keep up continuous monitoring and make normal water level observations on the stream flow monitoring sites, and to build up a special management system to enhance data reliability. The development of long term FDC for the unit watersheds can be established appropriately with the normal and durable measurement on the selected reference sites in the stream flow monitoring network.

• Journal of Korean Society on Water Environment
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• v.33 no.4
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• pp.394-402
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• 2017

In korea, TMDL is being implemented to manage nonpoint pollution sources as well as point pollution sources. LDC is being used for the planning of TMDL. In order to analyze the water quality using LDC, it is necessary to prepare FDC using the daily flow data. However, only the daily flow data is measured at the WAMIS branch, and 8days flow data and water quality data are measured at the monitoring Networks. So, in many researches, the water quality is being grasped by deriving the LDC using the 8days flow or the daily flow obtained by various methods. These fluctuations may lead to differences in determining whether the target load is achieved. In this study, each LDC was prepared using the 8day flow and the related daily flow. Then, the effect using different flow data on the achievement of target load was compared according to flow conditions. As a result, the difference ratio in the number of overloads under flow condition was showed 19% in high flows, 42% in moist conditions, 49% in mid-range flows, 41% in dry conditions, and 104% in low flows. In the top ten watershed with the highest difference ratio, the flow became lower the difference ration increases. These differences can cause uncertainty in assessing the achievement of target load using LDC. Therefore, in order to evaluate the water quality accurately and reliably using LDC, accurate daily flow data and water quality data should be secured through the installation of national nonpoint measurement network.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.301-302
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• 2002

Virtual cyclones have been the subject of aerosol separation studies since they were first developed by Torczynski and Rader (1996). In the virtual cyclone (originally referred to as the anticyclone), the main particle-laden flow follows a wall that curves away from the original flow direction rather than curving into the original direction, as in a cyclone. Although a wall forms the inner boundary of the main flow, its outer boundary is formed by an adjacent flow, often a confined recirculating flow, into which particles are transferred by centrifugal action. (omitted)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.353-360
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• 2010

The Kyunggi Bay in mid-west of Korea is a relatively large estuarine system that connects the Han River system with Yellow Sea. Due to macro-tidal range of more than 8 m, the urban estuary shows deep tidal channels and wide tidal flats. Since last 30 years, the coastal development is undergoing, yielding noticeable change in environment. Particularly the tidal flat dynamics are generally accepted as being related with tidal residual flows in this area (Kim et al., 2009). We have estimated the annual variation and vertical structure of residual currents with one-year long observed flows in two major tidal channels of Kyunggi Bay. The moving average method and tidal current harmonic analysis yield nearly the same results on residual flow. The residual flow in Jangbong channel ranges from 20 cm/s in summer to 30 cm/s in winter. It is noticeable that the residual flow in Jangbong channel is flood dominant throughout the year, while the flow in Seokmo channel is ebb-dominant residual flow with current speed range of 20-40 cm/s. Due to the baroclinic response of relatively shallow estuary, significant reduction of energy in bottom layers have been observed, indicating the importance of residual circulation to the tidal flat behavior.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.1
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• pp.55-68
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• 2012

Impervious surface increase due to urbanization, one of the leading causes of pavement increased the runoff coefficient, peak flow, and reducing the infiltration flow and thereby causing flooding and river erosion is occurring in aquatic ecosystems are known to impair. This study aimed to classify use type of detailed land into the road, reststop, tollgates and etc. focused on major domestic highways, to understand the characteristics of rainfall runoff pollutants and to calculate applicable unit pollution load. Because of high runoff coefficient and short travel time to drainage. first flush occurred clearly. Average EMCs of runoff in the highway was investigated as TSS 108.47 mg / L, COD 28.16 mg / L, BOD 13.61 mg / L, TN 6.38 mg / L, TP 0.03 mg / L, Cu 118.17 ${\mu}g$ / L, Pb 345.3 ${\mu}g$ / L, Zn 349.47 ${\mu}g$ / L. Unit pollution loads calculated by detailed land use area of highways based on average annual rainfall, EMCs, applicable basin areas and etc. were 46.6 kg/km2/day of BOD, 1.4 kg/km2/day of TP, 8.81 kg / km2/day of TN and these were BOD 50.8%, TP 66.7%, TN 64.4%in comparison of the unit pollution loads which applies fallow land standards of the TMDL(Total Maximum Daily Load). It was considered that discharged loads can be excessively calculated in case highway non-point management plans based on unit pollution load of the current land standard.

• The Journal of Information Technology
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• v.8 no.2
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• pp.85-91
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• 2005

We studied a pollution mechanism for simulation of contamination environment in industrial concentrated area of around a metropolitan that made to circulated flow in the chamber. In case of the virgin both side of EPDM or Silicon insulator, we confirmed that the pollution to much more than service insulator in the field. Also contamination of initial state of the virgin didn't falling in spite of physical outside factor easily. This study confirmed to that the silicon was too much accumulated pollution contrast to EPDM insulator from scatter(spray) point to regular interval position use the Kaolin contaminant in the chamber. There are effected to the hydrophobicity of polymer insulator due to the pollution. In ceramic insulator, we get to know that pollution is much more at the Post insulator with vertical than with horizontal setup insulator.

• Membrane and Water Treatment
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• v.9 no.4
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• pp.233-243
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• 2018

In this manuscript, $35m^3/d$ NF unit was designed and applied for surface water treatment of the River Nile water. Intake of Embaba drinking water treatment plant was selected to install that unit at since; it has the lowest water quality index value through the examined 6 sites in greater Cairo area. The optimized operating conditions were feed and permeate flow, 40 and $7m^3/d$, feed pressure 2.68 bar and flux rate $37.7l/m^2h$. The permeate water was drinkable according to Egyptian Ministerial decree 458/2007 for the tested parameters (physic-chemical, heavy metals, organic, algal, bacteriological and parasitological). Single and double sand filters were used as pretreatment for NF membranes but continuous clogging for sand filters moved us to use UF membrane as pretreatment for NF membrane.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.6
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• pp.97-109
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• 2018

The LDC (Load Duration Curve) method can analyze river water quality changes according to flow rate and seasonal conditions. It is also possible to visually recognize whether the target water quality is exceeded or the size of the reduction load. For this reason, it is used for the optimal reduction of TPLCs and analysis of the cause of water pollution. At this time, the flow duration curve should be representative of the water body hydrologic curve, but if not, the uncertainty of the interpretation becomes big because the damaged flow condition is changed. The purpose of this study is to estimate the daily mean flow of the unit watershed using the HSPF model and to analyze the difference of the flow duration curves according to the cumulative daily mean flow rate using the NSE technique. The results show that it is desirable to construct the flow duration curve by using the daily average flow rate of at least 5 years although there is a difference by unit watershed. However, this is the result of the water bodies at the end of Han River basin watershed, so further study on various water bodies will be necessary in the future.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.6
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• pp.83-92
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• 2005

Natural environment of the Wolgokri stream watershed, located in Chuncheon, Gangwon province, Korea, has been well preserved as a traditional agricultural watershed. To analyze characteristics of NPS pollution generated from an mountainous agricultural watershed, the flow and water qualities of the study watershed were monitored and were analyzed to estimate pollution loads. Annual runoff volume ratio was $70.4\%$. Concentrations of T-N, T-p, COD, and TOC were higher when monthly rainfall was between $0\~30mm$ than those when monthly rainfall was between $30\~70mm$. However, the concentrations varied considerably when monthly rainfall was higher than 100mm. The flow weighted mean concentrations(mg/L) of BOD, COD, TOC, $NO_3-N$, T-N, T-P and SS were 1.96, 2.72, 3.32, 1.41, 4.70, 0.187 and 13.36, respectively. The BOD, SS, T-N and T-P loads of July, 2004 were $48\%,\;17\%,\;51\%\;and\;32\%$ of annual load, respectively. The BOD, COD, TOC, $NO_3-N$, T-N, T-p, and SS loads (kg/ha) from Mar. 2004 to Apr. 2005 were 19.09, 26.55, 32.39, 13.85, 45.92, 1.887 and 130.18, respectively. The highest concentrations of BOD, NO3-N, T-N, T-p, SS, COD and TOC were found before the flow reached the peak runoff, possibly due to the first flushing effect. Generally, pollution loads of the Wolgokri watershed were not that significant. Phosphorus load, however, was higher enough to cause eutrophication in the receiving water body It was recommended that best management practices need to be implemented to reduce phosphorus sources.

• Journal of Korean Society on Water Environment
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• v.38 no.6
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• pp.306-315
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• 2022

In this study, long-term measurement data were applied to the LOADEST model and used as an analysis tool to identify and interpret trends in pollution load. The LOADEST model is a regression equation-based pollution load estimation program developed by the United States Geological Survey (USGS) to estimate the change in the pollution load of rivers according to flow rate and time and provides 11 regression equations for pollution load evaluation. As a result of simulating the Gwangjuchen2, Pungyeongjeongchen, and Pyeongdongchen in the Yeongbon B unit basin in the middle and upper reaches of the Yeongsan River with the LOADEST model using water quality and flow measurement data, lower values were observed for the Gwangjuchen2 and Pyeongdongchen, whereas the Pungyeongjeongchen had higher values. This was judged to be due to the characteristics of the LOADEST model related to data continuity. According to the parameters estimated by the LOADEST model, pollutant trends were affected by increases in the flow. In addition, variability increased with time, and BOD and T-P were affected by the season. Thus, the LOADEST model can contribute to water quality management as an analytical tool for long-term data monitoring.