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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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Korea Water Resources Association
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Volume & Issues
Volume 32, Issue 6 - Dec 1999
Volume 32, Issue 5 - Oct 1999
Volume 32, Issue 4 - Aug 1999
Volume 32, Issue 3 - Jun 1999
Volume 32, Issue 2 - Apr 1999
Volume 32, Issue 1 - Feb 1999
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A Numerical Method for Longitudinal Dispersion Equation for Nonconservative Contaminants
Yu, Myeong-Gwan ; Jeon, Gyeong-Su ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 607~616
A fractional step finite difference model for the longitudinal dispersion of nonconservative contaminants is developed. It is based on splitting the longitudinal dispersion equation into a set of three equations each to be solved over a one-third time step. The fourth-order Holly-Preissmann scheme, an analytic solution, and the Crank-Nicholson scheme are used to solve the equations for the pure advection, the first-order decay, and the diffusion, respectively. To test the model, it is applied to simulate the longitudinal dispersion of continuous source released into a nonuniform flow field as well as the dispersion of an instantaneous source in a uniform flow field. The results are compared with the exact solution and those computed by an existing model. Compared to the existing model which uses Euler method for the first-order decay equation, the present model yield more accurate results as the decay coefficient increases.
On the Change of Flood and Drought Occurrence Frequency due to Global Warming : 1. Change of Daily Rainfall Depth Distribution due to Different Monthly/Yearly Rainfall Depth
Yun, Yong-Nam ; Yu, Cheon-Sang ; Lee, Jae-Su ; An, Jae-Hyeon ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 617~625
Global warming has begun since the industrial revolution and it is getting worse recently. Even though the increase of greenhouse gases such as
is thought to be the main cause for global warming, its impact on global climate has not been revealed clearly in rather quantitative manners. However, researches using General Circulation Models(GCMs) has shown the accumulation of greenhouse gases increases the global mean temperature, which in turn impacts on the global water circulation pattern. This changes in global water circulation pattern result in abnormal and more frequent meteorological events such as severe floods and droughts, generally more severe than the normal ones, which are now common around the world and is referred as a indirect proof of global warming. Korean peninsula also cannot be an exception and have had several extremes recently. The main objective of this research is to analyze the impact of global warming on the change of flood and drought frequency. Based on the assumption that now is a point in a continuously changing climate due to global warming, we analyzed the observed daily rainfall data to find out how the increase of annual rainfall amount affects the distribution of daily rainfall. Obviously, the more the annual rainfall depth, the more frequency of much daily rainfall, and vice versa. However, the analysis of the 17 points data of Keum river basin in Korea shows that especially the number of days of under 10mm or over 50mm daily rainfall depth is highly correlated with the amount of annual rainfall depth, not the number of dry days with their correlation coefficients quite high around 0.8 to 0.9.
On the Change of Flood and Drought Occurrence Frequency due to Global Warming : 2. Estimation of the Change in Daily Rainfall Depth Distribution due to Global Warming
Yun, Yong-Nam ; Yu, Cheol-Sang ; Lee, Jae-Su ; An, Jae-Hyeon ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 627~636
In 60 years when the double
concentration is anticipated the average annual rainfall depth is expected to be increased by 5 10% due to global warming. However, in the water resources area the frequency change of meteorological extremes such as droughts and floods attracts more interests than the increase of annual rainfall amount. Even though recent frequent occurrences of this kind of meteorological extremes are assumed as an indirect proof of global warming, the prediction of its overall tendency has not yet been made. Thus, in this research we propose a possible methodology to be used for its prediction. The methodology proposed is based on the frequency distribution of daily rainfall be Todorovie and Woolhiser(1975), and Katz(1977), where the input parameters are modified to consider the change of monthly or annual rainfall depth and, thus, to result in the change of frequency distribution. We adopt two values(10mm, 50mm) as thresholds and investigate the change of occurrence probability due to the change monthly and annual rainfall depth. these changes do not directly indicate the changes of occurrence probability of floods and droughts, but it may still be a very useful information for their prediction. Finally, the changes of occurrence probability were found to be greater when considering the monthly rainfall rather than the annual rainfall, and those in rainy season than those in dry season.
Application of Generalized Transmissivity Decreasing Function in TOPMODEL Operation
Jeong, Seon-Hui ; Kim, Sang-Hyeon ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 637~647
This study investigated the applicability of generalized TOPMODEL approach which introduces the power law of decreasing transimissivity with depth instead of the traditional exponential decreasing function. The 50m digital elevation model(DEM) of Dongkog subwatershed at Wichon Test Watershed was used to perform runoff simulation. Random number generation algorithm was integrated into the calibration process for the reliable of model performance. General power law version of TOPMODEL with exponent 2 and 3 showed higher simulation efficiency than other the approaches. This results from the fact that the power law models with exponent 2 and 3 can represent the soil characteristics of study area better than other models.
A Study of Matimum Run-up Heights of Periodic Waves
Jo, Yong-Sik ; Lee, Bong-Hui ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 649~655
The maximum run-up heights of periodic waves are numerically investigated in this study. Incident waves are sinusoidal and enoidal waves. The maximum run-up height of enoidal wave approaches that of sinusoidal wave as the wave length decreases, while it approaches that of solitary wave as the wave length increases. If wave height is fixed, the maximum run up heights of enoidal waves are always greater than those of sinusoidal waves but smaller than those of solitary waves.
Calibration and Sensitivity Analysis of LRCS Rainfall-Runoff Model(I): Theory
O, Gyu-Chang ; Lee, Gil-Seong ; Lee, Sang-Ho ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 657~664
This paper introduced the basic theory of LRCS(Linear Reservoir and Channel System) rainfall runoff model proposed by Korean researchers(Lee and Lee, 1995), and discussed the change of model output according to objective functions in sensitivity analysis and calibration process of model. It proposed "hat" matrix and affluence measures for affluence analysis of parameters in calibration, and investigated relationship between change of model output according to error propagation in parameter estimation, and sensitivity of model output according to variance of model output and change of parameters. Accuracy of parameter estimates was known by analysis of sensitivity coefficient, diagonal element
Calibration and Sensitivity Analysis of LRCS Rainfall-Runoff Model(II) : Application
O, Gyu-Chang ; Lee, Gil-Seong ; Lee, Sang-Ho ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 665~674
This paper confirmed the applicability of model to Korean rivers through the calibration and sensitivity analysis of LRCS rainfall runoff model for 18 storm events of Songriweon station in Nakdong river system, and achieved that LS and WLS were better than LAD by model fitting results. Diagonal element of "hat" matrix and affluence measures were used by analysis of parameter estimates, and parameter IL was the most important parameter in model output. By the results of error propagation according to parameter error, parameters IL, TP, F1 were affected by error propagation, and this is measure of sensitivity for the model output. This paper confirmed the relationship of calibration and sensitivity analysis of model through analysis of sensitivity coefficient, diagonal element
Variation of Reflection Coefficients for a Shelf with Varying Dimensions
Jo, Yong-Sik ; Lee, Jong-In ; Kim, Yeong-Taek ; Lee, Jeong-Gyu ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 675~683
The reflection coefficients of monochromatic waves propagating over a shelf with varying dimensions are theoretically calculated. The diffraction of waves by an abrupt depth change is formulated by the eigenfunction expansion method. Not only propagating mode but also evanescent modes are considered in formulation. The role of evanescent modes in reflection coefficients is investigated in detail. Water waves are obliquely as well as normally incident to the region. The obtained reflection coefficients are verified by checking conservation of wave energy.
Improvement for Reservoir Operation Module of Flood Forecasting-Warning Systems in Han River
Gwon, O-Ik ; Kim, Seung ; Sim, Myeong-Pil ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 685~695
On the premise of flood control procedure, flood forecasting-warning, system(FFWS) is one of actions for disaster prevention. It makes public announcements for flood situations timely in order to mitigate damage from floodings. Multi-purpose dam which has flood control storage plays an important role in river basin at flood time. In FFWS, it is reservoir operation module that is related to reservoir operation of multi-purpose dam. This study considers the current conditions and problems in reservoir operation module of FFWS in Han River and improves reservoir operation module under limited research scope. As results, additional reservoir operation modules such as Technical ROM(Reservoir Operation Method) and ARD(Approved Release Discharge) ROM were built in FFWS. Using these newly built reservoir operation modules. Han River Flood Control Office will plan and work for flood control and flood forecasting. Firstly, it may plan for flood control by Technical ROM which is deterministic simulation model, and work for final flood control and flood forecasting by ARD ROM according to approved release discharge afterward.
Two Dimensional Numerical Simulation of Bed Change in the Reach near Buyeo Intake Station
Han, Geon-Yeon ; Lee, Eul-Rae ; Son, Gwang-Ik ; Im, Chang-Su ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 697~709
Two dimensional finite element model(RMA) is applied to examine sediment transport behavior near Buyeo water intake station of the Keum River. The simulation results of bed change with various discharge conditions agree with those of observation. As the alternatives of channel modification and resulting bed lowering near intake station, construction of jetties and removal of small island are considered. The station of jetties diverted the main stream toward the other side and the width of the main stream did not change so much. The bed elevation of the main channel is reduced about 5~20 cm, when flow condition of 12,030㎥/sec applied. The removal of small island provides the less significant effect on sediment movement. This study shows that the construction of jetties would be effective to reduce the entrainment of sediment.
Parameters Study of Linear Reservoir Models for Rainfall-Runoff Response
Seo, Yeong-Je ; Kim, Jin-Gyu ; Park, Hyeon-Ju ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 711~720
In this study, a various rainfall-runoff modelling approaches have been applied to the runoff response of flood hydrograph in three experimental watershed of the western part of korea. Mathematical models of runoff response also have been studied including linear system theory based on modeling techniques. Eight models were operated at the five water level gauging stations and the parameters of each model were computed by the Rosenbrock's hill climbing method to minimize the objective function. For the parameter verification of the models, a different complex rainfall-runoff event was selected in the same of the three river basins and derived IUH of the each model could be calibrated. Furthermore multiple regressions of the logarithmic transformation method between model parameters and catchment characteristics were studied in the selected five station.
GRID-based Daily Evapotranspiration Prediction Model (GRIDET)
Chae, Hyo-Seok ; Kim, Seong-Jun ; Jeong, Gwan-Su ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 721~730
A Grid-based daily evapotranspiration(ET) prediction model which calculates temporal and spatial ET with a complementary relationship of Morton(1983) was developed. The model was programmed by C-language and uses ASCII formatted map data of DEM(Digital Elevation Model) and land use. Daily ET within the watershed is calculated and the results of temporal variations and spatial distributions of ET are presented by using GRASS(Geographic Resources Analysis Support System). To verify the applicability of the model, it was applied to the part of Bocheong stream basin (76.5
) located in the upstream of Dacheong Dam watershed. The result shows that the estimated evapotranspiration in 1995 was 766.1mm and 22% increased after correction radiation for slope and area.
Nonlinear Analog of Autocorrelation Function
Kim, Hyeong-Su ; Yun, Yong-Nam ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 731~740
Autocorrelation function is widely used as a tool measuring linear dependence of hydrologic time series. However, it may not be appropriate for choosing decorrelation time or delay time
which is essential in nonlinear dynamics domain and the mutual information have recommended for measuring nonlinear dependence of time series. Furthermore, some researchers have suggested that one should not choose a fixed delay time
but, rather, one should choose an appropriate value for the delay time window
, which is the total time spanned by the components of each embedded point for the analysis of chaotic dynamics. Unfortunately, the delay time window cannot be estimated using the autocorrelation function or the mutual information. Basically, the delay time window is the optimal time for independence of time series and the delay time is the first locally optimal time. In this study, we estimate general dependence of hydrologic time series using the C-C method which can estimate both the delay time and the delay time window and the results may give us whether hydrologic time series depends on its linear or nonlinear characteristics which are very important for modeling and forecasting of underlying system.
Study on Characteristice of Transient Soulte Transport in the Vadose Zone by Using TDR: (1) Relationship between Water Content and Realtive Electrical Conductivity
Park, Jae-Hyeon ; Seo, Il-Won ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 741~749
This study is to develop a method of measuring the soil water concentration by using TDR, which is based on the relationships between the bulk soil electrical conductivity of soil and the reflected wave of TDR. The proposed monitoring method is combined with two important relationships. One is that between the bulk soil electrical conductivity and the solute concentration, which is known to be linear at a constant volumetric soil water content and the other is that between the relative bulk soil electrical conductivity and the water content at a constant concentration. Some formulas have been proposed to solve the second relationship, but a new formula and the critical water content are proposed to improve the accuracy of measurement. This proposed formula estimates the relative bulk soil electrical conductivity for water contents which is divided to two regions, linear and nonlinear, by the critical water content. As the result of the comparison with other formulas, the proposed formula is proved to be superior to other formulas and to be an available method to apply to the unsaturated transient solute transport.
Study on Characteristics of Transient Soulte Transport in the Vadose Zone by Using TDR: (2) Application
Park, Jae-Hyeon ; Seo, Il-Won ;
Journal of Korea Water Resources Association, volume 32, issue 6, 1999, Pages 751~762
In this study, a 1-D laboratory experiment was conducted to investigate the characteristics of transient unsaturated solute transport by using two kinds of soils of which properties were known by test. Especially the TDR method which is proposed in this study was used to measure water content and solute concentration. As results, in the transient flow, the wetting front moves down rapidly, and the distribution of solute concentration near the wetting front showed the similar type of the water content distribution(semi-bell type). A numerical model HYDRUS was used to compare with the experimental results. Numerical results for the water movement are similar to experimental result. However, numerical results of the distribution of solute concentration are more scattered than experimental results. It means that measured dispersivity, numerical dispersion, adsorption coefficient, and soil sample size etc. should be considered in order to determine the dispersivity used in the numerical model. The present measuring method was proved to be superior to other formula and to be an available method to apply to solute transport test. The measuring error of the developed method is estimated smaller than 10% while water content is larger than 0.15