• Journal of Korean Society of Water and Wastewater
• /
• v.35 no.6
• /
• pp.517-531
• /
• 2021

The water supply facilities of Korea have achieved a rapid growth, along with the other social infrastructures consisting a city, due to the phenomenon of urbanization according to economic development. Meanwhile, the level of water supply service demanded by consumer is also steadily getting higher in keeping with economic growth. However, as an adverse effect of rapid growth, the quantity of aged water supply pipes are increasing rapidly, Bursts caused by pipe aging brought about an enormous economic loss of about 6,161 billion won as of 2019. These problems are not only worsening water supply management, also increasing the regional gap in water supply services. The purpose of this study is to classify hazard evaluation indicators and to rank the water distribution network hazard by cluster using the TOPSIS method. In conclusion, in this study, the entropy-based multi-criteria decision-making methods was applied to rank the hazard management of the water distribution network, and the hazard management ranking for each cluster according to the water supply conditions of the county-level municipalities was determined according to the evaluation indicators of water outage, water leakage, and pipe aging. As such, the hazard ranking method proposed in this study can consider various factors that can impede the tap water supply service in the water distribution network from a macroscopic point of view, and it can be reflected in evaluating the degree of hazard management of the water distribution network from a preventive point of view. Also, it can be utilized in the implementation of the maintenance plan and water distribution network management project considering the equity of water supply service and the stability of service supply.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2022.05a
• /
• pp.475-475
• /
• 2022

The aim of this study is to identify the significant pollutant sources from the tributaries that are affecting the water quality of the study site, the Geum River and provide a solution to enhance the water quality. Multivariate statistical analysis modles such as cluster analysis, Principal component analysis (PCA) and positive matrix factorization (PMF) were applied to identify and prioritize the major pollutant sources of the two major tributaries, Gab-cheon and Miho-cheon, of the Geum River. PCA identifies three major pollutant sources for Gab-cheon and Miho-cheon, respectively. For Gab-cheon, wastewater treatment plant (WWTP), urban, and agricultural pollutions are identified as major pollutant sources. For Miho-cheon, agricultural, urban, and forest land are identified as major pollutant sources. On the contrary, PMF identifies three pollutant sources in Gab-cheon, same as PCA result and two pollutant sources in Miho-cheon. Water quality control scenarios are formulated and improvement of water quality in the river locations are simulated and analyzed with the Environmental Fluid Dynamic Code (EFDC) model. Scenario results were evaluated using a water quality index developed by Canadian Council of Ministers of the Environment. PCA and PMF appears to be effective to identify water pollution sources for the Geum river and also its tributaries in detail and thus can be used for the development of water quality improvement alternative of the above water bodies.

• Korean Journal of Ecology and Environment
• /
• v.55 no.2
• /
• pp.156-166
• /
• 2022

Understanding the characteristics of reservoir water quality is fundamental in reservoir ecosystem management. The water quality of reservoirs is affected by various factors including hydro-morphology of reservoirs, land use/cover, and human activities in their catchments. In this study, we classified 83 major reservoirs in South Korea based on nine physicochemical factors (pH, dissolved oxygen, chemical oxygen demand, total suspended solid, total nitrogen, total phosphorus, total organic carbon, electric conductivity, and chlorophyll-a) measured for five years (2015~2019). Study reservoirs were classified into five main clusters through hierarchical cluster analysis. Each cluster reflected differences in the water quality of reservoirs as well as hydromorphological variables such as elevation, catchment area, full water level, and full storage. In particular, water quality condition was low at a low elevation with large reservoirs representing cluster I. In the comparison of eutrophication status in major reservoirs in South Korea using the Korean trophic state index, in some reservoirs including cluster IV composed of lagoons, the eutrophication was improved compared to 2004~2008. However, eutrophication status has been more impaired in most agricultural reservoirs in clusters I, III, and V than past. Therefore, more attention is needed to improve the water quality of these reservoirs.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.87-91
• /
• 2011

강수는 지역에 따라 발생양상이 매우 다른 자연현상 중 하나이다. 이러한 강수를 효과적으로 분석하여 확률강수량을 산정하기위해서 수문학에서는 다양한 방법이 시도되어 왔다. 우리나라에서는 지점빈도해석을 통한 확률강수량을 주로 사용해왔으나 최근 들어 Hosking and Wallis(1997)가 제안한 지역빈도해석을 활용을 적극 도모 하고 있는 중이다. 이러한 지역빈도해석 기법은 지점빈도해석 기법에 비하여 한정된 강수자료를 활용하는 측면 등 여러 가지 장점을 가진 확률 강수량 산정방법이다. 그러나 이 기법을 적용하여 확률강수량을 산정하기 위해서는 강수의 지역구분을 먼저 수행하여야 한다. 강수지역의 구분을 위해서는 여러 가지 기법이 존재하나 최근에는 Cluster 기법 중 K-means 방법이나 Fuzzy c-means 방법 등을 주로 적용하여 지역구분을 수행하고 있다. 그러나 K-means 방법이나 Fuzzy c-means 방법 등은 산정 방법내에서 최적 군집수를 결정할 수 있는 알고리즘이 없기 때문에 임의적으로 최적 군집수를 결정하여야 한다. 본 연구에서는 이러한 단점을 극복하기 위하여 Cluster 평가지수 중 하나인 Dunn 지수를 이용하여 최적 군집수를 제시하고자 한다. 본 연구에서 강수지역을 구분하기 위하여 적용한 인자는 월 평균 강수량, 연 평균 강수량, 월 최대 강수량, 경도, 위도, 고도 등이며, 이를 K-means, PAM 및 친근도 전파 기법을 통하여 강수지역을 구분하였다. 적정 군집수를 임의적으로 증가시켜 가면서 Dunn 지수를 산정하였다. 산정된 결과를 통하여 최적 군집수를 결정하였다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.6-6
• /
• 2015

본 연구에서는 일단위로 제공되는 RCP 시나리오를 Poisson Cluster 기법을 활용하여 시간강우량으로 생성할 수 있는 모형을 개발하는데 목적이 있다. 일반적으로 시간단위 강우량의 경우 수자원 설계 또는 강우-유출 분석시 가장 기본이 되는 입력 자료로서 이에 대한 모의기법 확립이 기후변화에 따른 수문학적 영향 검토의 신뢰성을 결정짓는 핵심 요소이다. 그러나 국내 다수 연구를 살펴보면 기후변화 시나리오의 시 공간적 상세화 기법을 활용한 일단위 상세화 연구는 다수 존재하였지만, 일단이 이하의 시간적 규모에 대한 연구는 미진한 실정이다. 이러한 이유로 본 연구에서는 시단위 상세화 기법시 일반적으로 사용되고 있는 Poisson Cluster 기법을 활용하여 국내 실정에 맞는 시단위 상세화 기법을 개발고자 한다. 본 연구에서는 RCP 시나리오를 시단위강우량 자료로 생성하기 위해 다음과 같은 연구를 진행하였다. 첫째, 본 연구에서는 기상청에서 제공하는 RCP($27km{\times}27km$) 시나리오를 활용하였으며, 1km 격자 단위로 시공간적 상세화 기법을 수행하였다. 둘째, 시공간적으로 상세화 된 자료를 Poisson Cluster 기법을 기반으로 시간단위 자료를 생성하였으며, 기본적인 통계치(평균, 분산, 왜곡도 등)를 활용하여 관측값과 비교 분석 하였다. 마지막으로, 미래 기후변화 시나리오를 동일한 방법으로 시간단위 자료를 생성하고 연 최대값을 추출하여 빈도해석을 통해 미래 극치 확률강우량을 평가하였다. 본 연구 결과 시간단위 자료를 제공함으로써 미래 수자원 설계 및 영향평가를 효과적으로 수행할 것으로 기대되며, 수문기상변화 예측을 위한 신뢰성 있는 자료로 활용될 수 있을 것으로 판단된다.

• Journal of Korea Water Resources Association
• /
• v.35 no.2
• /
• pp.149-159
• /
• 2002

The monthly water quality data measured at 19 stations located in the Sapkyo reservoir watershed were clustered into 2 to 7 clusters and factor analysis was conducted to characterize the water quality, using the information obtained from cluster analysis. The result of cluster analysis shows that Sapkyo reservoir and each stream (Sapkyo stream, Muhan stream and Kokkyo stream) in Sapkyo reservoir watershed hove their own water quality characteristics. The result of water quality analysis indicates that the concentration of suspended solids from Sapkyo reservoir is much higher than those of other streams, and which is probably because of increment of phytoplankton biomass with rich nutrient flowing Into Sapkyo reservoir from the upper stream of watershed. Furthermore, the concentrations of biochemical oxygen demand and chemical oxygen demand were 3.5 to 4.8 times and 1.7 to 2.5 times those of other streams, respectively. The overall water quality of Sapkyo reservoir watershed was considered to exceed eutrophic condition. Based on factor analysis, the water quality characteristics of Sapkyo stream and Muhan stream were closely related with farm land and residence. The water quality of Kokkyo stream was influenced by superabundant organic matter flowing from Chonan city and district wastewater treatment plant located in the upper stream of Kokkyo stream. The water quality factor influencing Sapkyo reservoir was closely related with water quality factors of other three streams.

• Mass Spectrometry Letters
• /
• v.14 no.4
• /
• pp.147-152
• /
• 2023

The increasing demand for two-dimensional imaging analysis using optical or electronic microscopic techniques has led to an increase in the use of simple one-dimensional and two-dimensional mass spectrometry imaging. Among these imaging methods, secondary-ion mass spectrometry (SIMS) has the best spatial resolution using a primary ion beam with a relatively insignificant beam diameter. Until recently, SIMS, which uses high-energy primary ion beams, has not been used to analyze molecules. However, owing to the development of cluster ion beams, it has been actively used to analyze various organic molecules from the surface. Researchers and commercial SIMS companies are developing cluster ion beams to analyze biological samples, including amino acids, peptides, and proteins. In this study, a water droplet ion beam for surface analysis was realized. Water droplets ions were generated via electrospraying in a vacuum without desolvation. The generated ions were accelerated at an energy of 10 keV and collided with the target sample, and secondary ion mass spectra were obtained for the generated ions using ToF-SIMS. Thus, the proposed water droplet ion-beam device showed potential applicability as a primary ion beam in SIMS.

• Journal of Korea Water Resources Association
• /
• v.35 no.1
• /
• pp.109-124
• /
• 2002

This study is an effort to develop a stochastic model of precipitation series that preserves the pattern of occurrence of precipitation events throughout the year as well as several characteristics of the duration, amount, and intensity of precipitation events. In this study an event cluster model is used to describe the occurrence of precipitation events. A logarithmic negative mixture distribution is used to describe event duration and separation. The number of events within each cluster is also described by the Poisson cluster process. The duration of each event within a cluster and the separation of events within a single cluster are described by a logarithmic negative mixture distribution. The stochastic model for hourly precipitation occurrence process is fitted to historical precipitation data by estimating the model parameters. To allow for seasonal variations in the precipitation process, the model parameters are estimated separately for each month. an analysis of thirty-four years of historical and simulated hourly precipitation data for Seoul indicates that the stochastic model preserves many features of historical precipitation. The seasonal variations in number of precipitation events in each month for the historical and simulated data are also approximately identical. The marginal distributions for event characteristics for the historical and simulated data were similar. The conditional distributions for event characteristics for the historical and simulated data showed in general good agreement with each other.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.41 no.2
• /
• pp.134-139
• /
• 2008

To improve the oxygen-deficient water mass (ODW), the spatial and temporal variation in the water quality and characteristic of ODW occurrence were analyzed using yearly water quality data from 1989 to 2006 in Jinhae Bay, Korea. In addition, we estimated $ODW_{area},\;ODW_{vol.}$ and $ODW_R$ for Jinhae Bay. The overall water quality improved during the 2000s, based the annual variation in dissolved oxygen, chemical oxygen demand, etc. A cluster analysis classified Jinhae Bay into the southwestern, central, northern, and eastern regions. ODW occurred throughout the southwestern region in 1993 and 2002-2004, and the estimated $ODW_{vol.}$ was about $1.92km^3$. ODW did not occur in the eastern region because circulating seawater was exchanged in that part of Jinhae Bay. As ODW was generated every year in the southwestern region, this is the most polluted area in Jinhae Bay. The ODWR decreased in the northern region, showing that the water quality there has improved since a wastewater treatment plant began operating in 1994.

• Journal of Korean Society of Water and Wastewater
• /
• v.21 no.2
• /
• pp.165-175
• /
• 2007

Performance indicators haven't been used for the assessment of the wastewater treatment facility or management in Korea yet, therefore they are going to be important parts in wastewater utilities because they are used to understand present situation and to compare one with other wastewater utilities. In this study, we used performance indicators to assess the condition of wastewater utilities and they were divided into four categories (A, B, C, and D). A category represented the condition of the planning & construction and composed of wastewater supply, disaster defence and employees. B category represented maintenance of wastewater utilities and were composed of manhole, sewer, and technical employees. C category showed the operation efficiency of wastewater utilities and D category represented the environmental load. To analyze the situation of wastewater utilities overall, cluster analysis was performed using four categori' es indicators. And CCC (Cubic Clustering Criterion) and R-square were used to decide the proper number of clusters, and wastewater utilities of 48 cities were divided into 5 groups(I, II, III, IV, and V groups). Each cluster was analyzed by average and standard deviation to understand the situation of wastewater utilities. A group analysis showed that IV and V clusters were insufficient, B group showed that I and IV groups were insufficient, C group showed all clusters are above average, and D group was also like C group.