• Journal of Korea Water Resources Association
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• v.36 no.1
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• pp.87-104
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• 2003

A numerical model of surface runoff and river flow has been applied to small- and large-size catchment areas in order to investigate the physical characteristics of river flow during flood period. Several refinements are made on the existing model SIRG-RS for the ways of rainfall input through surface runoff, river junction treatment and the computation of river flow on steep slope. For the computation of frictional forces, employed is the power law of friction factor which is a function of Reynolds number and relative roughness height. The empirical equation of friction factor is developed using recent field data as well as laboratory data. The refined model has been applied to small-size catchment area as well as large-size catchment area, and the computation results are found in good agreement with the observations in both cases.

• Journal of Korean Society on Water Environment
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• v.39 no.1
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• pp.46-60
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• 2023

Climate change causes fluctuations in water quality in the aquatic environment, which can cause changes in water circulation patterns and severe adverse effects on aquatic ecosystems in the future. Therefore, research is needed to predict and respond to water quality changes caused by climate change in advance. In this study, we tried to predict the dissolved oxygen (DO), chlorophyll-a, and turbidity of the Paldang reservoir for about two weeks using long short-term memory (LSTM) and gated recurrent units (GRU), which are deep learning algorithms based on recurrent neural networks. The model was built based on real-time water quality data and meteorological data. The observation period was set from July to September in the summer of 2021 (Period 1) and from March to May in the spring of 2022 (Period 2). We tried to select an algorithm with optimal predictive power for each water quality parameter. In addition, to improve the predictive power of the model, an important variable extraction technique using random forest was used to select only the important variables as input variables. In both Periods 1 and 2, the predictive power after extracting important variables was further improved. Except for DO in Period 2, GRU was selected as the best model in all water quality parameters. This methodology can be useful for preventive water quality management by identifying the variability of water quality in advance and predicting water quality in a short period.

• Journal of the Korean association of regional geographers
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• v.20 no.2
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• pp.176-188
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• 2014

Since the late 1990s, a nationwide movement against dam and river-mouth weir plans in Japan has been promoted with a movement against a river-mouth weir for the Nagara river(長良川). This movement has been a catalyst for institutional frameworks on the central government's dam and river-mouth weir plans. Subsequently, water resource and river management policies have entered a new phase, with provinces governors's participation in "Statements on withdrawal from dam and river-mouth weir" as well as the seizing of power by the Democratic Party. However, problems with dams and river-mouth weirs have been confused due to poor countermeasures from the Democratic Party and to the Liberal Democratic Party(LDP)'s return to power. The fundamental causes on this situation are the non-establishment of fiscal norms for public projects and the rigidity of the water-right allocation system in Jananese policy-making processes. To successfully settle future policy on water resources and rivers, the first priority is to prepare specific institutional frameworks on finance of public projects and to organize a practical policy coordination system among government organizations. These policy tasks provide implications for river and water management policy in Korea.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.230-230
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• 2015

When and why do states cooperate in international basins? In recent years, there have been increasing attempts to apply international relations theories such as realism and neo-liberal institutionalism in understanding prospect of cooperation among sovereign states over shared rivers. Realists of hydropolitics argue that fate of cooperation resides in hands of hegemons and distribution of aggregate power among riparian states. Such pessimistic contention has been challenged by neo-liberal institutionalists, especially through regime theory. However, regime theory barely explains why and how cooperation emerges in the first place prior to regime formation. Therefore, the research suggests the game theory from neo-liberal institutionalism as an alternative theoretic approach. The accountability of Oye (1986)'s theoretical framework is illustrated through the case of cooperation in the Rhine River Basin.

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.151-163
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• 2012

The distribution of gravel-bed materials in mountainous river is formed by the process of deposition and transportation of sediment responding to stream power of the latest flood that is over the certain scale. The particle size of bed material was surveyed in the longitudinal points of river and detail points of a specific meandering section and used to estimate the critical velocity and stream power. Yang's critical unit stream power and Bagnold's critical stream power for gravel-bed materials increased with the distance from downstream to upstream. Dimensionless shear stress based on the designed flood discharge in Shields diagram was evaluated that the gravel-bed materials in most survey points may be transported as form of bedload. The mean diameter in the meandering section was the biggest size in first water impingement point of inflow water from upstream and the second big size in second water impingement point by reflection flow. The mean diameters were relatively the small sizes in points right after water impingement. The range of mean critical velocity was 0.77~2.60 m/s and critical unit stream power was big greatly in first water impingement point. The distribution of critical stream power, range of 7~171 $W/m^2$, was shown that variation in longitudinal section was more obvious than that of cross section and estimated that critical stream power may be affected greatly in first and second water impingement point.

• Journal of Magnetics
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• v.21 no.3
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• pp.431-436
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• 2016

In the design of transformer winding, natural vibration frequency is an important parameter. This paper presents a 2D model to calculate axial vibration natural frequency of power transformer winding based on the elastic dynamics theory, and according to the elastic support equivalent principle of radial pressboards. The 3D model to calculate natural vibration frequency can be simplified as a 2D one as the support of pressboards on the winding is same. It is verified that results of the 2D model are consistent with those of 3D one, but the former can achieve much higher calculation efficiency. It shows that increasing the width and number of pressboards can improve axial natural frequency through formula analysis and simulation, and also the relations between the changes of axial pre-compression and axial natural vibration frequency on the windings are investigated. Finally, the proposed 2D model's effectiveness is proved when compared with tested ones.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.495-507
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• 2016

This study aims at hydrologically demonstrating the universality of power law distribution by analyzing runoff aggregation structures of river basins. Power law distribution is fitted to cumulative drainage area of basins of interest by maximum likelihood, which results in the power law exponents. And then those exponents are assessed in terms of the shape of catchment plan-form. As a main result all of the basins in this study have similar distributions of catchment area. The exponents from this study tend to be higher than the ones from previous researches reflecting self-similar property of the catchment plan-forms of interest. Further study is required about the universality of power law distribution by means of the more realistic flow routing scheme within the framework of DEM.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.42-47
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• 2011

Small hydropower resources for five major river systems have been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the variation of inflow caused from rainfall condition. And another model to predict hydrologic performance for small hydropower(SHP) plants is established. Monthly inflow data measured at Andong dam were analyzed. The predicted results from the developed models in this study show that the data were in good agreement with measured results of long term inflow at Andong dam. It was found that the models developed in this study can be used to predict the available potential and technical potential of SHP sites effectively. Based on the models developed in this study, the hydrologic performance for small hydropower sites located in river systems have been analyzed. The results show that the hydrologic performance characteristics of SHP sites had some difference between the river systems. Especially, the specific design flow and specific output of SHP sites located on North Han river and Nakdong river systems had large difference compared with other river systems.

• The Journal of Society for e-Business Studies
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• v.20 no.4
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• pp.1-17
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• 2015

A river water level monitoring system which prevents salt water damages and effectively excludes floods has been developed to contribute efficient operation of Nakdong river estuary barrage. The system can be used for monitoring upstream conditions more quickly and do appropriate responses over changes. Telemetry and telecontrols using PLCs have been built at the three sites that directly influence on the operation of barrage gates, and are linked to Nakdong river estuary barrage's IOS (Integrated Operation System) through public communication networks. By using PLC, the system can achieve even higher reliability and versatility than before as well as easy management. By power control devices, we can remotely control the power of PLCs to treat the minor troubles instantly without going on-sites. The power control devices also save data in preparation for the cases of communication failures. The system uses ADSL (FTTH) as a main network between SCADA server and PLCs, and CDMA (M2M) as a secondary network. In order to compensate security vulnerabilities of public communication network, we have installed the VPNs for secure communication between center and the observation stations, just like a dedicated network. Generally, river water level observations have been used custom-manufactured remote terminals to suit their special goals. However, in this case, we have established a system with open architecture considering the interface between different systems, the ease of use and maintenance, security, price, etc.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1311-1315
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• 2009

Understanding of the hydraulics of flow is very important to support the management of river. The cross-sectional area, average velocity, flow depth and discharge can be regarded as a power function each other. In this paper the flow of Bocheong stream basin is experimentally studied. The correlation analysis was performed between observed hydraulic factors by the power type function. The constants resulted from the correlation analysis were calculated by the geomorphologic characteristics of the watershed using the power type function. The correlation coefficients between the hydraulic factors were appeared close to unit having strong correlationship. The two conditions of equality of the continuity equation were analysed, and the conditions were found to be good results. From these results the observed hydraulic data of Bocheong stream basin can be concluded as a reliable data. The correlation coefficients between the parameters of the hydraulic characteristics and geomorphologic factors were found to be close to unit.