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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korea Water Resources Association
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Journal DOI :
Korea Water Resources Association
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Volume & Issues
Volume 39, Issue 12 - Dec 2006
Volume 39, Issue 11 - Nov 2006
Volume 39, Issue 10 - Oct 2006
Volume 39, Issue 9 - Sep 2006
Volume 39, Issue 8 - Aug 2006
Volume 39, Issue 7 - Jul 2006
Volume 39, Issue 6 - Jun 2006
Volume 39, Issue 5 - May 2006
Volume 39, Issue 4 - Apr 2006
Volume 39, Issue 3 - Mar 2006
Volume 39, Issue 2 - Feb 2006
Volume 39, Issue 1 - Jan 2006
Selecting the target year
Re-evaluation of Change of Mean Velocity Profile in Open-Channel Turbulent Flows due to Sediment Particles
Yu Kwon-Kyu ; Yoon Byung-Man ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 727~735
DOI : 10.3741/JKWRA.2006.39.9.727
It is well known that sediment particles introduced in open-channel turbulent flows change mean velocity profile, since Vanoni suggested the reduction of the Karman constant in 1946. However, how the sediment particles take such a role and what parameters would be changed have been debated up to now. Some researchers, on the other hand, have insisted that the constant would not be changed regardless of introducing sediment particles. The present study is a careful re-evaluation of the previous studies on this issue. The study revealed some questionable approaches or methods in the decision of the previous researches and found the reason why this issue has been debated for a long time. The result indicated that the Karman number is reduced by adding sediment particles, but the amount of reduction is much smaller than the previous researches insisted. Finally, the present study proposes a mechanism of the Karman number reduction due to sediment particles.
An Inner Region Velocity-Profile Formula of Turbulent Flows on Smooth Bed
Yu Kwon-Kyu ; Yoon Byung-Man ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 737~744
DOI : 10.3741/JKWRA.2006.39.9.737
The velocity of the inner region of turbulent flow on a smooth bed has complex profile which can not be described with a simple formula. Though there have been a couple of formulas describing the profile, most of them have very complex forms, i.e., with many terms, with integration form, or with implicit forms. It means that it is hard to use them or it is difficult to estimate their parameters. A new single formula that describes the velocity profile of the inner region of the turbulent flow on a smooth bed was proposed. This formula has a form of the traditional log-law multiplied by a damping function. Introducing only one additional parameter, it can describe the whole inner range nicely. It approximates the law-of-the-wall in the vicinity of the bed and approaches to the log-law in the overlap region. The added parameter, damping factor, can be estimated very easily. It is not sensitive to the Reynolds number change and the velocity profile calculated by the formula does not change much due to the change of the parameter.
Analysis of Spatial Distribution of Droughts in Korea through Drought Severity-Duration-frequency Analysis
Kim Dae-Ha ; Yoo Chul-Sang ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 745~754
DOI : 10.3741/JKWRA.2006.39.9.745
This study adopted the Rectangular Pulses Poisson Process Model for the drought severity-duration-frequency analysis to characterize the spatial pattern of drought over the Korean peninsula using the rainfall data of the 59 rain gauge stations. First of all, the drought severity in the southern part of the Korean peninsula was found to be generally high for any return period. This result is consistent for both cases with and without considering the overlap probability of rectangular pulses, which is also valid for longer durations. Comparison with those of observed drought frequency and maximum severity also showed that the result in this study has enough reliability.
Use of Climate Information for Improving Extended Streamflow Prediction in Korea
Lee Jae-Kyoung ; Kim Young-Oh ; Jeong Dae-Il ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 755~766
DOI : 10.3741/JKWRA.2006.39.9.755
Since the accuracy of climate forecast information has improved from better understanding of the climatic system, particularly, from the better understanding of ENSO and the improvement in meteorological models, the forecasted climate information is becoming the important clue for streamflow prediction. This study investigated the available climate forecast information to improve the extended streamflow prediction in Korea, such as MIMI(Monthly Industrial Meteorological Information) and GDAPS(Global Data Assimilation and Prediction) and measured their accuracies. Both MIMI and the 10-day forecast of GDAPS were superior to a naive forecasts and peformed better for the flood season than for the dry season, thus it was proved that such climate forecasts would be valuable for the flood season. This study then forecasted the monthly inflows to Chungju Dam by using MIMI and GDAPS. For MIMI, we compared three cases: All, Intersection, Union. The accuracies of all three cases are better than the naive forecast and especially, Extended Streamflow Predictions(ESPs) with the Intersection and with Union scenarios were superior to that with the All scenarios for the flood season. For GDAPS, the 10-day ahead streamflow prediction also has the better accuracy for the flood season than for the dry season. Therefore, this study proved that using the climate information such as MIMI and GDAPS to reduce the meteorologic uncertainty can improve the accuracy of the extended streamflow prediction for the flood season.
A Study on the Improvement of Huff`s Method in Korea : I. Review of Applicability of Huff`s method in Korea
Jang Su-Hyung ; Yoon Jae-Young ; Yoon Yong-Nam ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 767~777
DOI : 10.3741/JKWRA.2006.39.9.767
The goal of this study is to improve Huff`s method which is the most popular method for rainfall time distribution in Korea. As the first step, we reevaluated the context of Huff`s original research motivations, geography and rainfall pattern of study area, and compared that to Korean situations. In original Huff`s results, no change in temporal distribution characteristics were found for different rainfall durations. This was found to be different from Korean situations. Furthermore, results from the MOCT(Ministry of Construction and Transportation) version of Huff`s method is on a gage basis not on a watershed basis, thus making it difficult to select cumulative rainfall curves representative of a watershed. In addition, all rainfall data regardless of their magnitude were used in the MOCT version of Huff` method which is different from original Huff`s which screened out data by using a threshold value of 25.4mm. For both point and areal mean rainfall, time distribution characteristics of rainfall for various durations were found to be different. This was statistically proven by K-S test at 5% significance level as some cumulative rainfall curves developed from the rainfall data of certain durations were found to be not significant with cumulative rainfall curves developed from the rainfall data of all durations. Therefore, in order to apply Huff`s method to Korean situations, it is recommended that dimensionless cumulative curve must be developed for various rainfall duration intervals using rainfall data greater than a certain threshold value.
A Study on the Improvement of Huff`s Method for Applying in Korea : II. Improvement of Huff`s Method
Jang Su-Hyung ; Yoon Jae-Young ; Yoon Yong-Nam ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 779~786
DOI : 10.3741/JKWRA.2006.39.9.779
In this study, we propose a new method that utilizes rainfall data in and out of a basin, which is greater than 25.4mm for point rainfall or 12.7mm for areal mean rainfall respectively. From our analysis, most frequent quartile for point and areal mean rainfall were found to be the same in general for various rainfall duration intervals. From an evaluation of design rainfall per each rainfall duration distributed in time by the MOCT(Ministry of Construction and Transportation) version of Huff`s method and this study, peak rainfall intensity by this study was found to be greater than the one by MOCT, but there were no consistent increase or decrease of this difference with rainfall durations. Using the distributed design rainfall per each duration by MOCT and this study, corresponding flood inflow hydrographs were simulated and compared each other. Contrary to the case of peak rainfall intensity, difference in peak flow by both methods per each rainfall duration started to increase from about 12-hr duration. Especially, the difference in peak flow was significant when critical rainfall duration was considered, and this trend was similar for peak flows of other rainfall durations. Therefore, the method proposed in this study is thought to be the effective procedure for the construction of dimensionless cumulative rainfall curve that is representative of a basin while considering time distribution characteristics for different rainfall durations.
Development of Drought Monitoring System: I. Applicability of Drought Indices for Quantitative Drought Monitoring
Lee Joo-Heon ; Jeong Sang-Man ; Kim Seong-Joon ; Lee Myung-Ho ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 787~800
DOI : 10.3741/JKWRA.2006.39.9.787
This study is to develop the drought monitoring system of Korea using drought indices such as PDSI, SPI and MSWSI. To analyze the applicability of three different drought indices, monthly based drought indices have been calculated using various kinds of meteorological and hydrologic data. Also past drought events have been investigated to compare the simulation results, which are the severity, duration and locations using monthly drought indices. The drought map which is made by using PDSI shows the best accordance with past drought events in its severity and duration as well. Also SPI(3) shows good accordance with past drought events. As a results of this study, we concluded that three different drought indices can be used as an effective tool for quantitative drought monitoring.
Development of Drought Monitoring System: II. Quantitative Drought Monitoring and Drought Outlook Methodology
Lee Joo-Heon ; Jeong Sang-Man ; Kim Jea-Han ; Ko Yang-Soo ;
Journal of Korea Water Resources Association, volume 39, issue 9, 2006, Pages 801~812
DOI : 10.3741/JKWRA.2006.39.9.801
In this study, Combined Drought Index which can monitor the drought severity and intensity has been developed using PDSI, SPI and MSWSI. To verify the accuracy and applicability of combined drought index, Drought map of Korea using the combined drought index has compared with past drought event. Drought map using the combined drought index shows good accordance with past drought event and accurate quantitative drought monitoring results. Also the drought outlook technique has been developed using the weather forecast data of Korea Meteorological Administration (KMA). Drought outlook technique of this study can be used effectively as a primitive stage tool for real time drought forecast. As a result of this study, Integrated drought monitoring system has been developed which has capabilities of producing and generating the drought monitoring map and drought outlook map as well as various kinds of drought related information.