• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.59-64
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• 2012

The correlation between hydrologic performance design parameters of small hydro power(SHP) sites and rainfall condition have been analyzed for major river systems. The model, which can predict flow duration characteristic of stream, was developed to estimate the inflow caused from rainfall. And another model to predict hydrologic performance for SHP plants is established. Based on the models developed in this study, the hydrologic performance characteristics for SHP sites have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems. It was found that the hydrologic performance design parameters such as specific design flowrate and specific output were affected by rainfall condition in basin area of SHP sites.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.2
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• pp.125-132
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• 1984

A physically-based, distributed, parametric hydrologic model PARK 10 is described and its test results with three agricultural watersheds are presented. The model uses a rectangular grid system to depict hydrologic characteristics of a watershed, and thus, has potentials of identifying the effects of changes in land uses and/or other activities. The model is being tested with small watersheds in the pennisula.

• KCID journal
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• v.17 no.2
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• pp.28-34
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• 2010

This study re-exams hydrologic stability on spillway outlet capacity of agricultural reservoirs using hydrologic data with current rainfall condition instead of project hydrologic data applied at design on Backgok reservoir located in Chungbuk province. It is concluded that Backgok reservoir is not hydrologically stable and therefore structural measures including the extension of spillway and non structural measures should be taken. Continuous basic plan for river maintenance including additional bank reinforcement to bottom river shall be carried out. Due to high peak flood with more than 290% compared to 200 year frequency probability flood which was design standard of the past in view of the results of calculating PMF according to revised design standard for reservoirs, there could a problem for securing rationality in case of applying PMF with design flood. Therefore, hydrological stability, construction, and maintenance cost shall be synthetically studied and reasonal application shall be made if the decision is made on applying PMF with design flood.

• Proceedings of the Korea Water Resources Association Conference
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• 1993.07a
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• pp.3-26
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• 1993

I have briefly described some of the important advances in hydrosystems and to remark on the important scientific research priorities in hydrological sciences. We have concentrated on data collection systems, real-time control of hydrosystems, global climate change and decision support systems and GIS. In summary, I would like to stress the following points: - the advances in data collection systems, advanced methodologies for interfacion hydrologic, hydraulic, and optimization models through optimal control approaches; and the advances in decision support systems and GIS will allow the interfacing of all these technologies into some sophisticated and much needed tools for operating hydrosystems; - the ability to better understand the hydrologic processes and their relationships to other earth processes is important to understanding and modelling of the hydrologic cycle and its interactions with the ocean-atmosphere system; - and the solution to a better understanding of hydrologic sciences needs to be an international effort such as the GEWEX program briefly discussed above. I would like to thamk each of you for listening to my lecture and to once again thank those responsible for me being here today. Thank you.

• Water for future
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• v.23 no.4
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• pp.421-434
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• 1990

The problems of hydrologic similarity among river basins was analyzed by a geomorphologic response model using Hortons*s ordering scheme. The Nash model was used for deriving the geomorphologic response function, and for the optimization of the responsefunction, imcomplete gamma function andRosso*s regression equation were used. The application of this method was tested on some observed flood data of Pyungchang river basin and Wi Stream basin and Bocheong stream, and predictions of hydrologic response were compared with that of the Moment method. The results show that the proposed model and dimensionless instantaneous unit hydrograph can be used for the runoff analysis of an ungauged basin and the analysis of hydrologic similarity.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.581-585
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• 2010

This study introduced a Bayesian based frequency analysis in which the statistical trend seasonal analysis for hydrologic extreme series is incorporated. The proposed model employed Gumbel and GEV extreme distribution to characterize extreme events and a fully coupled bayesian frequency model was finally utilized to estimate design rainfalls in Seoul. Posterior distributions of the model parameters in both trend and seasonal analysis were updated through Markov Chain Monte Carlo Simulation mainly utilizing Gibbs sampler. This study proposed a way to make use of nonstationary frequency model for dynamic risk analysis, and showed an increase of hydrologic risk with time varying probability density functions. In addition, full annual cycle of the design rainfall through seasonal model could be applied to annual control such as dam operation, flood control, irrigation water management, and so on. The proposed study showed advantage in assessing statistical significance of parameters associated with trend analysis through statistical inference utilizing derived posterior distributions.

• Journal of the Korean Solar Energy Society
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• v.30 no.2
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• pp.65-71
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• 2010

The hydrologic performance characteristics of small hydro power(SHP) sites located in four 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 SHP plants is established. Monthly inflow data measured at Andong dam for 32 years were analyzed. The predicted results from the developed models in this study showed that the data were in good agreement with measured results of long term inflow at Andong dam. The results from hydrologic performance analysis for SHP sites located on five major river systems based on the models developed in this study show that the specific design flowrate and specific output of SHP site have large difference between the river systems.

• Journal of Korea Water Resources Association
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• v.43 no.5
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• pp.483-493
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• 2010

In this study, for the purpose of analyzing variability and periodicity of Korean hydrologic weather parameters, 5 hydrologic weather parameters data such as annual precipitation, annual rainy days, annual average temperature, annual average relative humidity, annual duration of sunshine are collected from 63 domestic meteorological stations that has the hydrologic weather parameters records more than 30 years. And in this study the variability and periodicity using the statistical methods like Wald-Wolfowitz test, Mann-Whitney test, and Wavelet Transform about hydrologic weather parameters is analyzed. The results of statistical analysis of variability and periodicity can be summarized as follows: 1) Variability commonly appeared in annual average temperature and annual average relative humidity. 2) Annual precipitation, annual rainy days and annual duration of sunshine showed different results according to area. 3) Periodicity appeared in annual precipitation and annual rainy days but did not appeard in annual average temperature, annual average relative humidity and annual duration of sunshine.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.353-363
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• 2020

Hydrologic models can be classified into two types: those for understanding physical processes and those for predicting hydrologic quantities. This study deals with how to use the model to predict today's stream flow based on the system's knowledge of yesterday's state and the model parameters. In this regard, for the model to generate accurate predictions, the uncertainty of the parameters and appropriate estimates of the state variables are required. In this study, a relatively simple hydrologic partitioning model is proposed that can explicitly implement the hydrologic partitioning process, and the posterior distribution of the parameters of the proposed model is estimated using the Markov chain Monte Carlo approach. Further, the application method of the ensemble Kalman filter is proposed for updating the normalized soil moisture, which is the state variable of the model, by linking the information on the posterior distribution of the parameters and by assimilating the observed steam flow data. The stochastically and recursively estimated stream flows using the data assimilation technique revealed better representation of the observed data than the stream flows predicted using the deterministic model. Therefore, the ensemble Kalman filter in conjunction with the Markov chain Monte Carlo approach could be a reliable and effective method for forecasting daily stream flow, and it could also be a suitable method for routinely updating and monitoring the watershed-averaged soil moisture.

• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.568-580
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• 2020

Calibrating a conceptual hydrologic model necessitates selection of a calibration period that produces the most reliable prediction. This often must be chosen randomly, however, since there is no objective guidance. Observation plays the most important role in the calibration or uncertainty evaluation of hydrologic models, in which the key factors are the length of the data and the hydro-climate conditions in which they were collected. In this study, we investigated the effect of the calibration period selected on the predictive performance and uncertainty of a model. After classifying the inflows of the Hapcheon Dam from 1991 to 2019 into four hydro-climate conditions (dry, wet, normal, and mixed), a conceptual hydrologic partitioning model was calibrated using data from the same hydro-climate condition. Then, predictive performance and post-parameter statistics were analyzed during the verification period under various hydro-climate conditions. The results of the study were as follows: 1) Hydro-climate conditions during the calibration period have a significant effect on model performance and uncertainty, 2) calibration of a hydrologic model using data in dry hydro-climate conditions is most advantageous in securing model performance for arbitrary hydro-climate conditions, and 3) the dry calibration can lead to more reliable model results.