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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 47, Issue 12 - Dec 2014
Volume 47, Issue 11 - Nov 2014
Volume 47, Issue 10 - Oct 2014
Volume 47, Issue 9 - Sep 2014
Volume 47, Issue 8 - Aug 2014
Volume 47, Issue 7 - Jul 2014
Volume 47, Issue 6 - Jun 2014
Volume 47, Issue 5 - May 2014
Volume 47, Issue 4 - Apr 2014
Volume 47, Issue 3 - Mar 2014
Volume 47, Issue 2 - Feb 2014
Volume 47, Issue 1 - Jan 2014
Selecting the target year
Water Supply Performance Assessment of Multipurpose Dams Using Sustainability Index
Lee, Gwang-Man ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 411~420
DOI : 10.3741/JKWRA.2014.47.5.411
The water resources sustainability is becoming an important issue in consideration of hydrologic uncertainty by global warming and climate change. This study is to assess the water supply performance for the major multipurpose dams using sustainability index. Parameters, mostly utilized in water resources system assessment, are selected in respect of applicability and flexibility, and those parameters are used as a variable of the composite index. In practice, the composite index including reliability, resiliency, vulnerability and maximum deficit are applied to 15 multipurpose dams and 4 major basins. And to conclude, Daechungdam in the Geum river basin and Imhadam, Hapchondam and Namgangdam in the Nakdong river basin show low sustainability comparing with other dams. The Nakdong river basin needs to develop alternatives to improve water supply stability because it indicates the most poor sustainability level.
Climate Aridity/humidity Characteristics in Seoul According to Changes in Temperature and Precipitation Based on RCP 4.5 and 8.5
Rim, Chang-Soo ; Kim, Seong-Yeop ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 421~433
DOI : 10.3741/JKWRA.2014.47.5.421
In this study, monthly and annual aridity indices which are the ratios of precipitation to potential evapotranspiration in Seoul climate measurement station were analyzed for past 50 years (1961~2010), and the ratio of aridity index simulated by climate change scenarios (RCP 4.5 and 8.5) for each future period (2011~2040, 2041~2070, 2071~2100) to aridity index for the past period (1971~2000) was analyzed. Furthermore, 5 different potential evapotranspiration equations (FAO P-M, Penman, Makkink, Priestley-Taylor, Hargreaves) were applied to analyze the effect of potential evapotranspiration equation on estimating aridity index and aridity index variation ratio (%). The study results indicate that the monthly precipitation, average temperature and potential evapotranspiration were increased in each future period as compared to past period for both RCP 4.5 and RCP 8.5. Furthermore, winter period showed more significant increase of potential evapotranspiration than summer period, but aridity index showed different patterns as compared with potential evapotranspiration reflecting the influence of precipitation. Therefore, it is necessary to make preparation for the increment of winter evapotranspiration in terms of water resources management. The monthly and annual aridity indices based on future climate change scenarios were greatly different according to potential evapotranspiration equations; however, monthly and annual patterns of aridity index variation ratio (%) in the future period as compared to past period were very similar regardless of applied potential evapotranspiration equation.
Probabilistic Assessment of Hydrological Drought Using Hidden Markov Model in Han River Basin
Park, Yei Jun ; Yoo, Ji Young ; Kwon, Hyun-Han ; Kim, Tae-Woong ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 435~446
DOI : 10.3741/JKWRA.2014.47.5.435
Various drought indices developed from previous studies can not consider the inherent uncertainty of drought because they assess droughts using a pre-defined threshold. In this study, to consider inherent uncertainty embedded in monthly streamflow data, Hidden Markov Model (HMM) based drought index (HMDI) was proposed and then probabilistic assessment of hydrologic drought was performed using HMDI instead of using pre-defined threshold. Using monthly streamflow data (1966~2009) of Pyeongchang river and Upper Namhan river provided by Water Management Information System (WAMIS), applying the HMM after moving-averaging the data with 3, 6, 12 month windows, this study calculated the posterior probability of hidden state that becomes the HMDI. For verifying the method, this study compared the HMDI and Standardized Streamflow Index (SSI) which is one of drought indices using a pre-defined threshold. When using the SSI, only one value can be used as a criterion to determine the drought severity. However, the HMDI can classify the drought condition considering inherent uncertainty in observations and show the probability of each drought condition at a particular point in time. In addition, the comparison results based on actual drought events occurred near the basin indicated that the HMDI outperformed the SSI to represent the drought events.
A Study on the Changes of Return Period Considering Nonstationarity of Rainfall Data
Shin, Hongjoon ; Ahn, Hyunjun ; Heo, Jun-Haeng ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 447~457
DOI : 10.3741/JKWRA.2014.47.5.447
This research focuses on the changes of return period for nonstationary rainfall data in which exceedance or nonexceedance probability varies depending on time. We examined two definitions of return period under nonstationarity and also performed nonstationary frequency analysis using the nonstationary Gumbel model to investigate variations of return period in Korea. Seogwipo, Inje, Jecheon, Gumi, Mungyeong, and Geochang were selected as subject sites of application. These sites have a trend in rainfall data as well as having more than 30 years data. As the results of application, the return periods considering nonstationarity are different with those considering stationarity. The differences of return periods between nonstationarity and stationarity increase as growing return period increases. In addition, the return period using the expected waiting time method shows lower value than that using the expected number of event method.
An Experimental Study on Flow Characteristics for Optimal Spacing Suggestion of 45° Upward Groynes
Kim, Sung Joong ; Kang, Joon Gu ; Yeo, Hong Koo ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 459~468
DOI : 10.3741/JKWRA.2014.47.5.459
Groyne to control the direction and velocity of flow in rivers is generally installed for the purpose of protecting riverbanks or embankments from erosion caused by running water. In particular, as interest in river restoration and natural river improvement increases, groynes are proposed as a key hydraulic structure for local flow control and riparian habitat establishment. Groynes are installed mainly in groups rather than as individual structures. In case of groynes installed as a group, flow around the groynes change according to spacing in between the groynes. Therefore, groyne spacing is regarded as the most important factor in groyne design. This study aimed at examining changes of flows around and within the area of groynes that take place according to the spacing of groynes installed in order to propose the optimal spacing for upward groynes. To examine flow characteristics around groynes, this study looked at flows in main flow area and recirculation flow area separately. In main flow area, it examined the impact of flow velocity increasing as a result of conveyance reduction that is exerted on river bed stability in relation to changes in the maximum flow velocity according to installation spacing. As a factor causing impacts on scouring and sedimentation within the area of groynes, recirculation flow in the groyne area can lead problems concerning flow within the area and stability of embankment. As for recirculation area, an analysis was conducted on the scale of rotational flow and the flow around embankment that exerts impacts on stability of the embankment. In addition, a comparative analysis was carried with reference to changes of the central point of rotational flow that occur within the area of groynes. As a result of compositely examining the results, the appropriate installation spacing is proposed as min. four times-max. six times considering a decrease in flow velocity according to the installation of upward groynes, river bed stability and stability of embankments against counterflow within the area of groynes.
Development of Hierarchical Bayesian Spatial Regional Frequency Analysis Model Considering Geographical Characteristics
Kim, Jin-Young ; Kwon, Hyun-Han ; Lim, Jeong-Yeul ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 469~482
DOI : 10.3741/JKWRA.2014.47.5.469
This study developed a Bayesian spatial regional frequency analysis, which aimed to analyze spatial patterns of design rainfall by incorporating geographical information (e.g. latitude, longitude and altitude) and climate characteristics (e.g. annual maximum series) within a Bayesian framework. There are disadvantages to considering geographical characteristics and to increasing uncertainties associated with areal rainfall estimation on the existing regional frequency analysis. In this sense, this study estimated the parameters of Gumbel distribution which is a function of geographical and climate characteristics, and the estimated parameters were spatially interpolated to derive design rainfall over the entire Han-river watershed. The proposed Bayesian spatial regional frequency analysis model showed similar results compared to L-moment based regional frequency analysis, and even better performance in terms of quantifying uncertainty of design rainfall and considering geographical information as a predictor.
Economic Design of Activated Sludge System at the Optimum Sludge Concentration
Lee, Byung Joon ; Choi, Yun Young ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 483~490
DOI : 10.3741/JKWRA.2014.47.5.483
The design procedures for a biological reactor and a secondary settling tank (SST) of an activated sludge system are based on the steady state design method (Ekama et al., 1986; WRC, 1984) and the 1-D flux theory design method (Ekama et al., 1997), respectively. This study combined both of the design procedures, to determine the optimum sludge concentration in the reactor and the best design with the lowest cost. The best design of the reactor volume and the SST diameter at the optimum sludge concentration were specified with varying wastewater and sludge characteristics, temperature, sludge retention time (SRT) and peak flow rate. The effects of the influent wastewater characteristics, such as substrate concentration and unbiodegradable particulate fraction, were found to be considerable, but the effect of unbiodegradable soluble fraction was to be negligible. The effects of sludge settling characteristics, were also significant. SRT, as an operating parameter, was found to be an important factor for determining the optimum sludge concentration. However, the effect of temperature was found to be small. Furthermore, for designing a large scale wastewater treatment plant, the number of reactors or SSTs could be estimated, by dividing the total reactor volume or SST area. The new combined design procedure, proposed in this research, will be able to allow engineers to provide the best design of an activated sludge system with the lowest cost.
Application of Streamflow Drought Index using Threshold Level Method
Sung, Jang Hyun ; Chung, Eun-Sung ;
Journal of Korea Water Resources Association, volume 47, issue 5, 2014, Pages 491~500
DOI : 10.3741/JKWRA.2014.47.5.491
To estimate the severity of streamflow drought, this study introduced the concept of streamflow drought index based on threshold level method and Seomjingang Dam inflow was applied. Threshold levels used in this study are fixed, monthly and daily threshold, The
analysis results of annual drought, the severe hydrological droughts were occurred in 1984, 1988 and 1995 and the drought lasted for a long time. Annual compared to extreme values of total water deficit and duration, the drought occurred in 1984, 1988, 1995 and 2001 was serious level. In the results of study, because a fixed threshold level is not reflect seasonal variability, at least the threshold under seasonal level was required. Threshold levels determined by the monthly and daily were appropriate. The proposed methodology in this study can be used to forecast low-flow and determine reservoirs capacity.