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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 49, Issue 8 - Aug 2016
Volume 49, Issue 7 - Jul 2016
Volume 49, Issue 6 - Jun 2016
Volume 49, Issue 5 - May 2016
Volume 49, Issue 4 - Apr 2016
Volume 49, Issue 3 - Mar 2016
Volume 49, Issue 2 - Feb 2016
Volume 49, Issue 1 - Jan 2016
Selecting the target year
Analyzing the drought event in 2015 through statistical drought frequency analysis
Lee, Taesam ; Son, Chanyoung ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 177~186
DOI : 10.3741/JKWRA.2016.49.3.177
Drought is a water-related natural disaster which can be simply described as spatially and temporally sequential absence of water. However, its characteristics are very difficult to define. For this reason, the preparation and mitigation from drought events have not been successful. In the current study, we illustrated a design drought estimation approach of water resources infrastructures as well as the existing theoretical one to prepare and mitigate drought disasters. Theoretical and simulation methods were tested including three time series models such as autoregressive (AR), Gamma AR, Copula AR models. The results indicated that for South Korea region, the simulation-based method to estimate drought frequency presented better performance and all the three time series models show similar performance to each other. The current drought event occurring in South Korea was investigated with dividing South Korea into four basins as Han River, Nakdong River, Geum River, and Nakdong River basins. The results showed that two middle and north basins presented significant drought events with 3 year drought duration and around 40 year return period while the other two southern regions illustrated relatively weaker drought events.
Characteristics of the Han River Basin drought using SPEI and RDI
Won, Kwang Jai ; Chung, Eun-Sung ; Lee, Bo-Ram ; Sung, Jang Hyun ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 187~196
DOI : 10.3741/JKWRA.2016.49.3.187
Standardized Precipitation Evapotranspiration Index (SPEI) considering evapotranspiration and precipitation is generally used to quantify the drought severity. Also, Reconnaissance Drought Index (RDI) has been frequently used in the arid regions which is suffering severe droughts, but drought analysis in association with RDI has been the focus of few studies in South Korea. Therefore, this study compared two meterological drought indices based on precipitation and evapotranspiration using Thornthwaite, Hargreaves, and Blaney-Criddle evaportranspiration calculation methods. Meteorological data of sixteen weather stations which are operated by Korea Meteorological Administration (KMA) were used to quantify drought and to compare characteristics of drought for the Han River Basin from 1992 to 2015. As a result, in case of Han River Basin, severe drought sharply increased in recent years. While the correlation coefficients are relatively high between the SPEIs and RDIs, the drought severity and year of severe drought are partially different. Therefore, it is necessary that RDI will be also measured to quantify severity and occurrence year of drought.
Correlation analysis between climate indices and Korean precipitation and temperature using empirical mode decomposition : I. Data decomposition and characteristic analysis
Ahn, Si-Kweon ; Choi, Wonyoung ; Kim, Taereem ; Heo, Jun-Haeng ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 197~205
DOI : 10.3741/JKWRA.2016.49.3.197
Recently, natural hazards have occurred frequently due to climate change. The research need for predicting variability and tendency of precipitation and temperature has been increased. However, it is difficult to determine the characteristics of precipitation and temperature within a confidence range since they change due to complex factors with choppy and too many components. If their characteristics having more than one component are decomposed, then it can be useful for determining the variation of such characteristics more accurately. In this study, Korean precipitation and temperature were decomposed and their Intrinsic Mode Function (IMF) were extracted from Empirical Mode Decomposition (EMD). Finally, the characteristics of Korean precipitation and temperature data were analyzed in terms of periodicity and tendency.
Correlation analysis between climate indices and Korean precipitation and temperature using empirical mode decomposition : II. Correlation analysis
Ahn, Si-Kweon ; Choi, Wonyoung ; Shin, Hongjoon ; Heo, Jun-Haeng ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 207~215
DOI : 10.3741/JKWRA.2016.49.3.207
In this study, it is analyzed how large scale climate variation has an effect on climate systems over Korea using correlation analysis between climate indices and Intrinsic Mode Functions (IMFs) of precipitation and temperature. For this purpose, the estimated IMFs of precipitation and temperature from the accompanying paper were used. Furthermore, cross correlation coefficients and lag time between climate indices and IMFs were calculated considering periodicities and tendencies. As results, more accurate correlation coefficients were obtained compared with those between climate indices and raw precipitation and temperature data. We found that the Korean climate is closely related with climate variations of
in terms of periodicity and its tendency is followed with increasing sea surface temperature due to climate change.
Estimation of drought risk through the bivariate drought frequency analysis using copula functions
Yu, Ji Soo ; Yoo, Ji Young ; Lee, Joo-Heon ; Kim, Tea-Woong ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 217~225
DOI : 10.3741/JKWRA.2016.49.3.217
The drought is generally characterized by duration and severity, thus it is required to conduct the bivariate frequency analysis simultaneously considering the drought duration and severity. However, since a bivariate joint probability distribution function (JPDF) has a 3-dimensional space, it is difficult to interpret the results in practice. In order to suggest the technical solution, this study employed copula functions to estimate an JPDF, then developed conditional JPDFs on various drought durations and estimated the critical severity corresponding to non-exceedance probability. Based on the historical severe drought events, the hydrologic risks were investigated for various extreme droughts with 95% non-exceedance probability. For the drought events with 10-month duration, the most hazardous areas were decided to Gwangju, Inje, and Uljin, which have 1.3-2.0 times higher drought occurrence probabilities compared with the national average. In addition, it was observed that southern regions were much higher drought prone areas than northern and central areas.
Estimation of spatial evapotranspiration using Terra MODIS satellite image and SEBAL model in mixed forest and rice paddy area
Lee, Yong Gwan ; Jung, Chung Gil ; Ahn, So Ra ; Kim, Seong Joon ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 227~239
DOI : 10.3741/JKWRA.2016.49.3.227
This study is to estimate Surface Energy Balance Algorithm for Land (SEBAL) daily spatial evapotranspiration (ET) comparing with eddy covariance flux tower ET in Seolmacheon mixed forest (SMK) and Cheongmicheon rice paddy (CFK). The SEBAL input data of Albedo, Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI) from Terra MODIS products and the meteorological data of wind speed, and solar radiation were prepared for 2 years (2012-2013). For the annual average flux tower ET of 302.8 mm in SMK and 482.0 mm in CFK, the SEBAL ETs were 183.3 mm and 371.5 mm respectively. The determination coefficients (
) of SEBAL ET versus flux tower ET for total periods were 0.54 in SMK and 0.79 in CFK respectively. The main reason of SEBAL ET underestimation for both sites was from the determination of hot pixel and cold pixel of the day and affected to the overestimation of sensible heat flux.
Numerical investigation of space effects of serial spur dikes on flow and bed changes by using Nays2D
Lee, Kyung Su ; Jang, Chang-Lae ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 241~252
DOI : 10.3741/JKWRA.2016.49.3.241
In this study, the characteristics of flow and bed changes with variation of space and length of serial spur dikes were investigated with 2 dimensional numerical simulation. Upstream spur dike was affected by flow and made a role as a single spur dike. As time increased, local scouring was developed around outside of spur dike, and migrated upstream. The aggradation of the bed at the back of spur-dike was made at the initial stage of experiment and numerical modelling. However, the aggradation of the bed was increased in the downstream area. The scour whole around a spur dike upstream was not deep as the Dimensionless spur-dike interval (b) of the dike increased. The depth of scour hole was nearly constant at the dynamic equilibrium state. The dimensionless scour depth (
) increased with L/b. The spur dike downstream had the characteristics of single spur dike as the L/b was larger than 10. However, the spur dike downstream was affected by the dike upstream as the L/b was less than 4, and the bed of the upstream in the spur dike was aggradated and the effects of the serial spur dikes on the bed decreased.
A development of rating-curve using Bayesian Multi-Segmented model
Kim, Jin-Young ; Kim, Jin-Guk ; Lee, Jae Chul ; Kwon, Hyun-Han ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 253~262
DOI : 10.3741/JKWRA.2016.49.3.253
A Rating curve is a regression equation of discharge versus stage for a given point on a stream where the stream discharge is measured across the stream channel with a stage and discharge measurement. The curve is generally used to calculate discharge based on the stage. However, the existing approach showed problems in terms of estimating uncertainty associated with regression parameters including the separation parameter for low and high flow. In this regard, this study aimed to develop a new method for the aforementioned problems based on Bayesian approach, which can better estimate the parameter and its uncertainty. In addition, this study used a Bayesian Multi-Segmented (Bayesian M-S) model which is provided a comparison between the existing and proposed scheme. The proposed model showed better results for the parameter estimation than the existing approach, and provided better performance in terms of estimating uncertainty range.
Spatial merging of satellite based soil moisture and in-situ soil moisture using conditional merging technique
Lee, Jaehyeon ; Choi, Minha ; Kim, Dongkyun ;
Journal of Korea Water Resources Association, volume 49, issue 3, 2016, Pages 263~273
DOI : 10.3741/JKWRA.2016.49.3.263
This study applied conditional merging (CM) spatial interpolation technique to obtain the satellite and in-situ composite soil moisture data. For the analysis, 24 gages of hourly in-situ data sets from the Rural Development Administration (RDA) of Korea and the satellite soil moisture data retrieved from Advanced Microwave Scanning Radiometer-Earth observing system (AMSR-E) were used. In order to verify the performance of the CM method, leave-one-out cross validation was used. The cross validation result was spatially interpolated to figure out spatial correlation of the CM method. The results derived from this study are as follow: (1) The CM method produced better soil moisture map over Korean Peninsula than AMSR-E did for the over 100 days out of total 113 days considered for the analysis. (2) The method of CM showed high correlation with gage density and better performance on the western side of Korean peninsula due to high spatial gauge density. (3) The performance of CM is not affected by the non-rainy season unlike to AMSR-E data is. Overall, the result of this study indicates that the CM method can be applied for predicting soil moisture at ungaged locations.