• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.236-243
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• 2007

Fluorescence measurements of dissolved organic matter (DOM) have the superior advantages over other analysis tools for the applications to water quality management due to their rapid analysis. It is known that protein-like fluorescence characteristics are well corelated with microbial activities and biodegradable organic matter. In this study, potential biochemical oxygen demand (BOD) predictor were explored using the fluorescence peak intensities and/or the integrated fluorescence intensities derived from synchronous fluorescence spectra and the first derivative spectra of river samples. A preliminary study was conducted using a mixture of a river and a treated sewage to test the feasibility of the approach. It was demonstrated that the better BOD predictor can be derived from synchronous fluorescence spectra and the derivatives when the difference between the emission and the excitation wavelengths (${\Delta}{\gamma}$) was large. The efficacy of several selected fluorescence parameters was rivers in Seoul. The fluorescence parameters exhibited relatively good correlation coefficients with the BOD values, ranging from 0.59 to 0.90. Two parameters were suggested to be the optimum BOD predictors, which were a fluorescence peak at a wavelength of 283 nm from the synchronous spectrum at the ${\Delta}{\gamma}$ value of 75 nm, and the integrated fluorescence intensity of the first derivatives of the spectra at the wavelength range between 245 nm and 280 nm. Each BOD predictor showed the correlation coefficients of 0.89 and 0.90, respectively. It is expected that the results of this study will provide important information to develop a real-time efficient sensor for river BOD in the future.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.195-195
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• 2016

Kon - Ha Thanh River basin is the largest and the most important river basin in Binh Dinh, a province in the South Central Coast of Vietnam. In the lower rivers, frequent flooding and inundation caused by heavy rains, upstream flood and or uncontrolled flood released from upstream reservoirs, are very serious, causing damage to agriculture, socio-economic activity, human livelihood, property and lives. The damage is expected to increase in the future as a result of climate change. An advanced flood warning system could provide achievable non-structural measures for reducing such damages. In this study, we applied a modelling system which intergrates a 1-D river flow model and a 2-D surface flow model for simulating hydrodynamic flows in the river system and floodplain inundation. In the model, exchange of flows between the river and surface floodplain is calculated through established links, which determine the overflow from river nodes to surface grids or vice versa. These occur due to overtopping or failure of the levee when water height surpasses levee height. A GIS based comprehensive raster database of different spatial data layers was prepared and used in the model that incorporated detailed information about urban terrain features like embankments, roads, bridges, culverts, etc. in the simulation. The model calibration and validation were made using observed data in some gauging stations and flood extents in the floodplain. This research serves as an example how advanced modelling combined with GIS data can be used to support the development of efficient strategies for flood emergency and evacuation but also for designing flood mitigation measures.

• Journal of Korea Water Resources Association
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• v.51 no.spc
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• pp.1057-1066
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• 2018

Climate change has been influenced on extreme precipitation events, which are major driving causes of flooding. Especially, most of extreme water-related disasters in Korea occur from floods induced by extreme precipitation events. However, future climate change scenarios simulated with Global Circulation Models (GCMs) or Reigonal Climate Models (RCMs) are limited to the application on medium and small size rivers and urban watersheds due to coarse spatial and temporal resolutions. Therefore, the current study introduces the state-of-the-art approaches and procedures of statistical downscaling techniques to resolve this limitation It is expected that the temporally downscaled data allows frequency analysis for the future precipitation and estimating the design precipitation for disaster prevention.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.53-59
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• 2018

Water pollution is drastically increasing day by day, because of the enhancement in use of livestock, urban sewage detergents and fertilizers. Moreover increase in concentration of phosphorous and nitrogen contained in sewage, leads to green tide problem in the rivers and causes marine pollution. For this problem to solve, several technologies are being researched and developed. Among them, this experiment is a study on Bench-scale STP based on internationally certified sewage treatment equipment by MEPC. 227(64) of IMO. The purpose of this study is to compare the biological treatment efficiency of phosphorus of Bench-scale STP. The ratio of C : N : P was set to 10 : 5 : 3 and 10 : 3 : 1 as the operating conditions. And the operation cycle was set to anoxic(mixed) 70 min - aeration 50 min (70-50), anoxic(mixed) 90 min - aeration 60 min (90-60). As a result, the phosphorous treatment efficiency was 88% at average, and the treatment efficiency was steady at 90-60 better than 70-50. The efficiency of the bench-scale STP has been verified through this experiment and additional experiments are required to derive the optimal operating conditions.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.448-448
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• 2023

도심 속 하천과 그 주변 지역(이하 수변)은 물과 자연환경이 주는 정서적 안정감과 쾌적함, 그리고 건강성을 대표하는 공간으로 도심 속 쉼터이자 힐링의 장소이다. 최근 수변이 도시경관의 질향상, 휴식 및 여가 공간 제공의 기능뿐만 아니라 열섬효과 완화 등 기후변화 대응에 효과가 있다는 사실도 재조명되면서, 수변이 도시의 발전과 활성화를 이끌어낼 새로운 동력이자 대안으로 급부상하고 있다. 본 연구에서는 서울의 4대 권역하천인 중랑천, 탄천, 안양천, 홍제천을 대상으로 하천과 하천 주변 500m 이내 구역을 하천공간과 수변공간으로 구분하고, 그 현황과 특성을 분석하였다. 하천(제방)으로부터 50m 이내 수변공간에 위치한 도로면적의 비율은 탄천이 40%로 가장 높았으며, 그 외에도 중랑천은 31%, 홍제천과 안양천은 28%로 하천변 도로면적비가 매우 높은 것으로 분석되었다. 특히, 중랑천은 하천공간 내 도로면적이 하천변 50m 이내에 위치한 도로의 면적과 비슷한 수준으로 나타났다.안양천, 중랑천, 탄천 대부분의 구간에서는 친수활동을 하기엔 다소 수심이 낮고(0.3m 이하) 유속이 느린 것(0.3m/s 이하)으로 분석되었고, 수질은 대부분의 구간에서 대장균 군수가 기준치를 수십에서 수백 배 초과하고 있어, 최상류 일부 구간을 제외한 전 구간에서 수영·물놀이 등 수상활동이 부적합한 것으로 분석되었다. 서울시민들은 주로 금요일과 토요일, 오후 12시에서 18시 사이에 하천을 가장 많이 방문하며 평균 2시간 정도를 머물렀으며, 대부분 걷기와 산책 활동을 하는 것으로 조사되었다. 도보, 대중교통 등 교통수단에 따른 하천진출입로 인근평균인구 대비 접근 가능 인구비율을 산출하여 접근성을 분석한 결과, 중랑천과 홍제천에서는 수변지역 내 평균인구의 20~30%가 도보 및 대중교통으로 20~30분 이내에 도달 가능한 것으로 분석되어 접근성이 가장 우수하였고, 안양천은 수변지역 내 평균인구의 15~20%가 30분 이내 도달가능하였으며, 탄천은 수변지역 내 평균인구의 10%미만이 30분 내에 도달가능한 것으로 분석되어 탄천의 접근성이 가장 열악한 것으로 나타났다.

• Korean Journal of Remote Sensing
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• v.39 no.4
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• pp.425-440
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• 2023

Monitoring water surface has become one of the most prominent areas of research in addressing environmental challenges.Accurate and automated detection of watersurface in remote sensing imagesis crucial for disaster prevention, urban planning, and water resource management, particularly for a country where water plays a vital role in human life. However, achieving precise detection poses challenges. Previous studies have explored different approaches,such as analyzing water indexes, like normalized difference water index (NDWI) derived from satellite imagery's visible or infrared bands and using k-means clustering analysis to identify land cover patterns and segment regions based on similar attributes. Nonetheless, challenges persist, notably distinguishing between waterspectralsignatures and cloud shadow or terrain shadow. In thisstudy, our objective is to enhance the precision of water surface detection by constructing a comprehensive water database (DB) using existing digital and land cover maps. This database serves as an initial assumption for automated water index analysis. We utilized 1:5,000 and 1:25,000 digital maps of Korea to extract water surface, specifically rivers, lakes, and reservoirs. Additionally, the 1:50,000 and 1:5,000 land cover maps of Korea aided in the extraction process. Our research demonstrates the effectiveness of utilizing a water DB product as our first approach for efficient water surface extraction from satellite images, complemented by our second and third approachesinvolving NDWI analysis and k-means analysis. The image segmentation and binary mask methods were employed for image analysis during the water extraction process. To evaluate the accuracy of our approach, we conducted two assessments using reference and ground truth data that we made during this research. Visual interpretation involved comparing our results with the global surface water (GSW) mask 60 m resolution, revealing significant improvements in quality and resolution. Additionally, accuracy assessment measures, including an overall accuracy of 90% and kappa values exceeding 0.8, further support the efficacy of our methodology. In conclusion, thisstudy'sresults demonstrate enhanced extraction quality and resolution. Through comprehensive assessment, our approach proves effective in achieving high accuracy in delineating watersurfaces from satellite images.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.463-463
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• 2022

도시하천은 급속한 경제성장과 개발 등 여건변화에 따라 크게 변화되어왔다. 이에 하천은 본연의 모습과 가치를 잃고 인공적인 모습으로 변해 하천의 주요 기능인 자정작용, 생태계 건강성 유지 등의 기능을 잃고 도시 활동에 따른 오염물질에 노출되어가고 있는 실정이다. 이로 인한 부정적인 영향으로 도시민의 삶의 질과 만족도 또한 하락되고 있다. 본 연구에서는 부산의 대표하천인 수영강을 대상으로 도시하천 수질 개선을 위한 도시민의 지불의사를 추정하였다. 비시장가치를 추정하기 위해 조건부가치측정법(CVM, Contingent Valuation Method)을 적용하여 수질개선에 따른 지불의사(WTP, Willingness To Pay)를 파악하고 경제적 가치를 추정하였다. 가상시나리오는 EPA, water quality ladder의 개념을 이용하여 현재 수영강 수질이 오염된 물(4등급)이라고 가상시장을 설정하고 낚시가 가능한 수준(2등급)까지 개선을 시키고자 할 때의 지불의사를 물었다. 이때 지불수단은 기부금의 형태로 연 1회 향후 5년간 지불기간을 설정하였다. WTP 모형추정은 KDI에서 제시하고 있는 로지스틱분포 함수와 스파이크 모형을 사용하여 WTP를 추정하였다. 스파이크 모형의 추정결과 평균 지불의사액은 12,255원으로 부산광역시 전체 가구 수인 1,392,291가구(2019년)에 적용할 경우 향후 5년간 연 170억 원의 재원을 확보할 수 있는 것으로 나타났다. 지불의사 추정결과 수영강 인접 지역주민의 지불의사가 높게 추정되었고, 부산시민이 수영강을 자연과 생태보전 기능하천으로 인지하고 있음(56.5%)을 고려 할 때, 하천환경개선을 통한 지불의사의 상승은 도시하천 가치 향상이 될 수 있을 것으로 판단된다. 또한 도시민의 기대수준 충족과 더불어 도시하천 가치상승을 위한 부족한 재원까지도 조달 할 수 있는 방안의 기초를 마련 할 수 있을 것이라 판단된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.467-467
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• 2022

1990년대 후반부터 시작된 자연형 하천정비 사업은 기존의 수질보전정책 외에도 하천생태계에 대한 관심이 부각되는 계기로 작용하고 있다. 이 중 환경생태유량은 기존의 하천유지유량보다 확대된 개념으로 수생태계 건강성 회복을 위한 중요한 요소이다. 본 연구에서는 도시하천 수생태계 건강성 회복방안 마련을 위한 기초자료 마련을 위해 부산의 대표적인 도시하천인 온천천과 학장천을 대상으로 환경생태유량을 산정하였다. 환경생태유량은 하천의 물리적 특성 및 어류·유량을 조사하는 하천현장조사, 서식지적합도지수 산정의 과정을 통해 산정된다. 온천천과 학장천에서 각각 3개의 대표지점을 선정하고 각 지점별로 2회의 현장조사를 통해 각 지점에서의 수심, 유속, 하상재료, 어류 조성을 조사하였다. 조사결과를 바탕으로 붕어와 참갈겨니를 대표어종으로 선정하고 Instream Flow and Aquatic Systems Group(IFASG, 1986)에서 제시한 방법을 이용하여 서식지적합도지수를 산정한 후, 미국지질조사국의 물리적서식지모의시스템(PHABSIM)을 이용하여 하천별, 어종별 환경생태유량을 산정하였다. 온천천의 경우, 붕어와 참갈겨니 모두 약 0.7~0.8m³/s에서 가용서식지면적이 가장 크게 산정되어 일 60,000~70,000m³ 가량의 환경생태유량 공급이 필요한 것으로 나타났다. 학장천의 경우, 붕어는 약 0.6~0.7m³/s, 참갈겨니는 약 0.3~0.4m³/s에서 가용서식지면적이 가장 크게 산정되어, 각각 일 50,000~60,000m³, 25,000~35,000m³ 가량의 환경생태유량이 필요한 것으로 나타났다. 본 연구로부터 산정된 환경생태유량을 금번 관측유량 및 현재의 하천유지용수 공급계획량과 비교해보면 온천천에서는 일 15,000m³ 이상, 학장천에서는 어종에 따라 일 7,000m³ 이상의 추가유량 확보가 필요한 것을 알 수 있었다. 특히 학장천의 경우, 어종에 따른 환경생태유량의 차이가 크게 나타나 하천 구간별 유량조사를 통해 어종별 주요 서식지 구간 설정 및 관리가 필요할 것으로 판단된다.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.3
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• pp.531-538
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• 2024

While the importance of the water quality environment is being emphasized, the water quality index for improving the water quality of urban rivers in Gwangju Metropolitan City is an important factor affecting the aquatic ecosystem and requires accurate prediction. In this paper, the XGBoost and LightGBM machine learning algorithms were used to compare the performance of the water quality inspection items of the downstream Pyeongchon Bridge and upstream BanghakBr_Gwangjucheon1 water systems, which are important points of Gwangju Stream, as a result of statistical verification, three water quality indicators, Nitrogen(TN), Nitrate(NO3), and Ammonia amount(NH3) were predicted, and the performance of the predictive model was evaluated by using RMSE, a regression model evaluation index. As a result of comparing the performance after cross-validation by implementing individual models for each water system, the XGBoost model showed excellent predictive ability.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.6
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• pp.1-19
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• 2023

This study aimed to identify the characteristics of the plant growth forms within the Amsa-dong Ecological and Landscape Conservation Area, a floodplain along the Han River, based on 20 years of flora monitoring data. The analysis revealed that there were 106 taxa identified in 2003, 158 taxa in 2006, 107 taxa in 2013, and 202 taxa in 2020. Compared to 2003 and 2013, the number of taxa increased significantly by approximately 50 taxa in 2006 and around 100 taxa in 2020. It is presumed that this is due to the influx of seeds caused by the flooding of the Han River due to record-breaking heavy rains during the rainy seasons of 2006 and 2020, leading to a rapid increase in the number of taxa. This was also confirmed in aquatic plants(HH) as a result of comparison of life style analysis by year. The analysis revealed that there were 19 aquatic plant(HH) in 2003, 32 aquatic plant(HH) in 2006, 9 aquatic plant(HH) in 2013, and 30 aquatic plant(HH) in 2020. The number of aquatic plants(HH) increased slightly in 2006 and 2020 compared to 2003 and 2013, and the influx of rare aquatic plants in urban rivers was confirmed. Consistent with the results of the vascular flora analysis above, these plants are believed to have been introduced from the upper reaches of the Han River when the Han River flooded due to heavy rains during the record-breaking rainy season in 2006 and 2020.