• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.167-176
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• 2015

The water quality of the Gulpo Stream flowing through Incheon, Bucheon, Seoul, and Kimpo is getting worse due to a slow flow rate and bank constructions by stream channelization as well as an inflow of pollutants from living-sewages and factory-sewages. Besides, a dry stream phenomenon caused by a lack of maintenance water upstream makes a self-purification system worse, and the water quality of the Gulpo Stream is currently at its lowest level. The accumulated sludge of the streambed is mostly formed by the deposition of particle pollutants due to the slow flow rate and an artificially straightened stream channel. This accumulated sludge adsorbs a great quantity of organic materials and heavy metals. Because of the internal contamination possibility by a re-gushing, even after the pollution source is removed, it can cause future water pollution. Without a total examination as previously recommended, it is considered difficult to accomplish practical efficiency. In conclusion, the management of periodic sediment management such as dredging would be necessary in the Gulpo Stream because sediment could be an internal pollution source of stream water under anaerobic conditions.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.94-100
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• 2013

In this study, we have investigated the water quality and flow rate at the 3 sites of main stream and 11 sites of the branch stream of Hwang River from January, 2007 to 2010, and analyzed the effects on Hwang River with the purpose of using the data for as the fundamental information for water quality improvement and water resource management in the water system of Hap-Cheon Lake Upper Stream. The flow rate at 3 sites of the main stream and 11 sites of the branch stream increased during the rainy season between June and September, and continuously decreased during the dry season starting from autumn to winter. The results of correlation analysis with Pearson correlation coefficient showed that $BOD_5$ and $COD_{Mn}$, $BOD_5$ and T-P, and $COD_{Mn}$ and TSS at the 3 sites of the main stream had high correlation with each other. We have also analyzed the correlation between Chl-a and major factors at the 3 sites of the main stream. Chl-a and the water temperature Negative correlation coefficient and that of Chl-a and $BOD_5$, $COD_{Mn}$ Positive correlation coefficient showed. The N/P ratio at all the 3 sites of the main stream was higher than 16 by DIN/DIP and T-N/T-P, indicating that phosphorus is acting as the limited nutrient.

• Journal of Korean Society of Forest Science
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• v.108 no.2
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• pp.224-232
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• 2019

The movement of fish to the upper and the lower parts of a mountain stream was investigated based on the installation of specific types of structures within the stream. The results indicated that as the flow rate increases after a rain, the height of the drop in an open-type structure, such as a concrete box, is decreased so that the floating fishes, such as the Chinese minnow fish, move relatively easily from the upper to the lower parts and from the lower to the upper parts of the stream. In contrast, the fishes released from an upper point of a wall-type structure with <1 m, such as rocks drop works and stone masonry for stream-grade stabilization, were trapped in the lower part of the stream and, even after the rainy season, it was difficult for the fish to move from the lower to the upper parts of the stream. In particular, the barrier-type structures ${\geq}3m$ limit the movement of fish, even when there are few drainage holes at the lower end of the dam, and there is no space for the fishes to communicate with each other, even when the flow rate is high; therefore, although the fish are active, they are restricted to move according to the type and characteristics of the structures. When installing structures in a mountain stream, the height of the structure must be low enough to allow the fish to communicate with each other or an open-type structure must be installed. The fish habitat and water conditions within the stream must be considered when designing the type and height of the in-stream structures.

• Journal of Korea Water Resources Association
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• v.54 no.3
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• pp.203-215
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• 2021

In the present study, hydrologic data and topographical data from 2010 to 2019 were collected from three gauging stations placed in the watershed of Naeseong stream to determine changes and rates of changes in rainfall, water level & mean velocity, and water level & discharge, together with changes in rates of erosion and deposition at cross-sections of the river. Besides, effects of regulated and non-regulated rivers according to the presence of artificial regulation of flow rate of the river via artificial structure located at Seo stream (Yeongju si (Wolhogyo) station), the tributary free from construction of dams, were compared and analyzed. Results of analyses conducted in the present study revealed vegetational establishment and landforming due to increasing area of vegetational sandbar evolved in the flood plain (intermediate- or high- water level) by the drought sustained from 2013 to 2015. Continuous erosion of river bed was appeared because of narrowed flow area with low water level and increased velocity and tractive force on river bed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.181-188
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• 2002

Water flow rate into the tunnel usually determined by numerical analyses and mathematical formulas using water levels and permeability is obtained only a few limited districts of the whole tunneling site. However, underground is not a homogeneous but complicated mass. Therefore these methods can't reflect structural and geological aspects. In this study, assuming that the mountain stream in droughty season is to be the same as baseflow of its basin, hydrological method is applied to predict the constant water flow rate into the tunnel on construction field. Prediction of constant water inflow rate is performed on each section of tunnel construction field divided into 20 sections.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.3
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• pp.24-39
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• 1982

It has already been known that quenching effect is influenced greatly by stirring and changing coolant's temperature on quenching. But according to the past investigations its effect has not been taken into consideration quantitatively in the cooling process. The purpose of this study is that the influence of flow rate and temperature on the quenching effect of cooling water as quenching medium is quantitatively examined by using the open channel. The stream of water in this study is turbulent flow. The temperature of the specimen made of pure copper is measured by CA thermocouple in the vicinity of the surface and recorded by an automatic recorder during the quenching process in city water. The results obtained are as follows; 1. The quenching effect of cooling water generally increases with Reynolds Number(characteristic length; specimen diameter)as shown in the experimental formula; but at the realm of Reynolds Number from 1.2 * 10$^{4}$ to 9.2 * 10$^{4}$, the increasing rate of quenching effect shows little increase. 2. The increasing rate of quenching effect was increased under the flow rate of 221 cm/sec. On the other hand, it was decreased below this flow rate. 3. The quenching effect was influenced by the water temperature and the flow rate. But it was rather dependent upon the former than the latter. 4. Although the quenching effect appeared loosely in the water temperature of 50.deg. C, it was shown that the quenching effect increased in the low flow rate of 31 cm/sec. comparing with the still water. 5. It is desirable to design the quenching system to be over 1.2 * 10$^{4}$ in Reynolds Number or over, 3000$cm^{-1}$ / in V/v in order to increase the quenching effect of the system using open channel.annel.

• Journal of Korea Water Resources Association
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• v.53 no.2
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• pp.89-96
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• 2020

Water management agencies under the Ministry of Environment produce and accumulate qualified basic data for major rivers. However, the integrated management of the river water has been weak since the artificial water circulation process, such as the intaking and drainage of agricultural water, has not been examined in the basin, which includes many agricultural land. In this study, a study was conducted on how the power usage method (operating time method) based on the running time can be applied and improved among indirect flow rate measurement methods used to investigate flow rates collected by the riverside for agricultural water purposes, and thus the resultant data of high reliability can be obtained at low cost. The operation time method is suitable for small-scale water pumping stations where it is difficult to secure real-time power supply data. The reliability of the data was verified through the correlation analysis with the actual flow rate, and it was found that the flow rate calculated by the operation time method reflecting the level of the stream to which the inlet of the pumping station is connected can be reasonably matched with the actual flow rate. In addition, it was confirmed that the investment cost at the time of initial installation of the facility was highly efficient by generating qualified flow data at low cost through comparison with direct flow rate measurement methods. If flow data is secured by applying the operation time method to large and small water farms located along the riverside, it is expected that more quantitative and integrated stream water management will be possible.

• Journal of Environmental Science International
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• v.16 no.3
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• pp.333-345
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• 2007

As analyzed the estimated values of the daily delivery loads from thirteen major side streams such as Naesung-river, Keumho-river, Hwang-river, Nam-river during five years (from 1999 to 2003), the daily BOD inflow into the main stream of Nakdong river in 2003 shows the highest quantity as 31.1 ton and the daily BOD inflows in 1999, 2000, 2001, and 2002 are 26.7 ton, 22.5 ton, 21.0 ton, 25.8 ton, respectively. The daily TN in-flow into the main stream of Nakdong river in 2003 shows also the highest quantity as 64.9 ton and the daily TN inflows in 1999, 2000, 2001, and 2002 are 55.19 ton, 46.27 ton, 39.5 ton, 53.38 ton, respectively. The daily TP inflow into the main stream of Nakdong river in 2003 shows the highest quantity as 2.70 ton likewise and the daily TP inflows in 1999, 2000, 2001, and 2002 are 2.17 ton, 1.87 ton, 1.60 ton, 2.10 ton, respectively The rate of BOD loads from each side main stream into the main stream of Nakdong river shows that the BOD loads of Keumho-river are the highest as the values range from 32.8 % (2002) ${\sim}$ 35.1 % (2003) and the BOD loads of Nam-river, Naesung-river, Hwang-river are high in the order named. The rate of TN loads to the main stream is also similar to the trend of BOD loads. The contribution of the TN loads of Geumho-river to the contamination of the main stream is also the highest having a range from 27.0 % (2002) to 28.8 % (1999) among the main side streams and the TN loads of Naesung-river, Nam-river, and Heachun-river are high in the order named. The rate of TP loads is quite different from the trend of BOD and TN loads. The TP rate of Keumho-river, however, is still the highest as ranging 58.6 % (2002) to 61.7 % (2003) and the river has the biggest portion (over 50%) of the entire pollution to the main stream of Nakdong river.

• The KSFM Journal of Fluid Machinery
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• v.9 no.3 s.36
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• pp.44-48
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• 2006

Comprehensive experimental works are carried out for the optimal design of a centrifugal blower adopted in an indoor unit of an air-conditioner. The models for consideration are typical multi-blade turbo blower and limit loaded one, respectively. The main interest lies on the fluid dynamics performance when the blower Is installed in the practical system. The methodologies are an experimental estimations with a wind tunnel for blower performance and PIV measurement for the detail flow information. A centrifugal blower with limit loaded fan shows pronounced performances in terms of the flow rate and static pressure rise and the reason is explained by the precise measurement of the flows between blades using PIV. Consequently, it is found that the blower is proper for the flows with a resistance in down stream such as a heat exchanger.

• Journal of Korean Society on Water Environment
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• v.33 no.6
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• pp.650-660
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• 2017

In this study, pollutant emission characteristics by water damage period analyzed 11 items (water temperature, pH, DO, EC, BOD, COD, TOC, SS, T-N, T-P and flow) with load duration curve, time series load curve and factor analysis for three years (2014-2016). Load duration curve is applied to judge the level of impaired waterbody and estimate impaired level by pollutants such as BOD and T-P in this study depending on variation of stream flow. Water quality standard exceeded the flow of mid-range and low-range by flow condition evaluation using load duration curve. This watershed was influenced by point source more than non-point source. Cumulative excess rate of BOD and T-P kept water quality standard for all seasons (spring, summer, autumn and winter) except BOD 59% in spring. Water quality changes were influenced by pollutants of basic environmental treatment facilities and agricultural areas during spring and summer. Results of factor analysis were classified commonly first factor (BOD, COD, and TOC) and second factor (flow, water temperature and SS). Therefore, effects of artificial pollutants and maintenance water must be controlled seasonally and reduced relative to water damage caused by point pollution sources with effluent standard strengthened in the target watershed.