• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.85-94
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• 2009

This study examines the operational effectiveness of a Convection Current Aeration System (CCAS) in reservoir. CCAS was run from June, 2008 when the thermocline begun forming in the reservoir. This paper reviews the influence of stratification, dissolved oxygen dynamics and temperature in the lake's natural state from June to October 2008. The survey was done on a week basis. Upwelling flow effects a radius of $7{\sim}10m$ at a surface directly and was irrelevant to the strength of thermocline. On the other hand, it was affected the number of working days, and strength of thermocline at vertical profiles of the reservoir. Longer CCAS run, the deeper was the vertical direct flow area. However it didn't break the thermocline during summer season of 2008. The operating efficiency of the CCAS in the reservoir depends on hydraulics and meteological conditions. Computational Fluid Dynamics (CFD) is a very useful tool for evaluating the operating efficiency of fluid dynamics. The geometry for CFD simulation consists of a cylindrical vessel 25 m radius and 40 m height. The CCAS is located in center of domain. The non-uniform tetrahedral meshes had a bulk of the geometry. The meshes ranged from the coarse to the very fine. This is attributed to the cold water flowing into the downcomer and rising, creating a horizontal flow to the top of the CCAS. The result of CFD demonstrate a closer agreement with surveyed data for temperature and flow velocity. Theoretical dispersion volume were calculated at 8m depth, 120 m diameter working for 30 days and 10 m depth, 130 m diameter working for 50 days.

• Korean Journal of Environment and Ecology
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• v.28 no.3
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• pp.314-325
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• 2014

We studied fish fauna at 10 study sites in Ungcheon stream for 4 times from April to October, 2011 to investigate the influence of artificial structures such as dam (with fish-way) and weir (without fish-way), and abandoned mine on fish community. A total of 12 families, 36 species of fishes were collected. Dominant species was Zacco platypus (23.4%) and subdominant species was Zacco koreanus (20.5%). Ten species (27.8%) of Korean endemic species and Micropterus salmoides, exotic species, were observed during the study period. Endangered species of Korea such as Pseudopungtungia nigra and Liobagrus obesus, and Korean endemic species, Coreoperca herzi, which are vulnurable for water quality and had been observed in previous study, were not identified in this study. According to the cluster analysis, Ungcheon stream were divided into three groups consisting upstream (St.1, St.2, St.3), midstream (St.4, St.5, St.6, St.7), downstream (St.8, St.9, St.10). Community structure similarity between upper and lower site of Boryeong dam with fish-way (St.6-St.7) was high, whereas that of weir, lack of fish-way (St.7-St.8) showed little similarity indicating that fish-way was required. According to the canonical correlation analysis, high level of conductivity and salinity at upstream was detected and Misgurnus mizolepis, and endemic species of Korea such as Silurus microdorsalis, Coreoleuciscus splendidus and Iksookimia koreensis were observed at this part of the stream. Since Korean endemic species, Squalidus gracilis majimae cohabit with exotic species, M. Salmoides at downstream whose width is wide and water velocity is low, protection was needed for these endemic species.

• Korean Journal of Environment and Ecology
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• v.34 no.3
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• pp.216-223
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• 2020

This study investigated the ecological characteristics of Coreoperca herzi at Jaho stream from September 2018 to August 2019. This species inhabited riffle and midstream of the stream, where the riverbed structure was mostly covered with cobble and pebble. The depth of the habitat was 32-157 cm, and the velocity of stream fast at 0.64±0.28 (0.32-1.28) m/sec. The gender ratio of females to males was 1:0.95. The age according to the frequency analysis of total length indicated that the group with 42-80 mm in total length was one year old, the group with 80-130 mm was two years old, the group with130-200 mm was three years old, and the group over 200 mm was four years old. The total length of sexually mature fishes was 65 mm for females and 70 mm for males. The sexually mature individuals grown in nature had a smaller total length than those reared in a laboratory. The spawning season was from May to late July, and the water temperature was 18.4-26.4℃ during the period. The prosperous spawning season was from May to June, and the water temperature was 18.4-21.8℃ during the period. The average number of eggs in the ovaries was 462 (151-919) per mature female, and the matured eggs were yellowish and spherical with a mean diameter of 2.31±0.33 (1.93-3.10) mm. Calculation length-weight relation of Korean aucha perch showed the constant a as 0.00002 and b as 3.01, condition factor (K) as 1.76 (1.01-2.63) on average, and the slope was a positive value of 0.0005.

• Journal of Digital Convergence
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• v.15 no.11
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• pp.245-250
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• 2017

Flash floods is defined as the flooding of intense rainfall over a relatively small area that flows through river and valley rapidly in short time with no advance warning. So that it can cause damage property and casuality. This study is to establish the flash-flood warning system using 38 accident data, reported from the National Disaster Information Center and Land Surface Model(TOPLATS) between 2009 and 2012. Three variables were used in the Land Surface Model: precipitation, soil moisture, and surface runoff. The three variables of 6 hours preceding flash flood were reduced to 3 factors through factor analysis. Decision tree, random forest, Naive Bayes, Support Vector Machine, and logistic regression model are considered as big data methods. The prediction performance was evaluated by comparison of Accuracy, Kappa, TP Rate, FP Rate and F-Measure. The best method was suggested based on reproducibility evaluation at the each points of flash flood occurrence and predicted count versus actual count using 4 years data.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.507-520
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• 2003

A V-shaped riffle is an artificial hydraulic structure haying two wings from the streamside with a narrow opening in between. It is usually made of crushed stones or large boulders. It limits channel width and accelerates the flow through the constricted section causing a local scour just downstream. The V-shaped riffle provides with a unique aquatic habitat by forming a pool and sandbars around the pool edge, increasing local morphologic, hydraulic and sedimentological diversity. This study investigates experimentally the scour characteristics of the V-shaped riffle in the sandbed stream and proposes a predictive equation for the scour. Total 45 cases of experiments were conducted to examine the effect of hydraulic factors and configuration of V-shaped riffle on the geometry of scour holes. From the comparison of the experimental results of this study with the predictive equation of spur dike by Breusers and Raudkivi(1991), it is found that their predictive equation of spur dike underestimates the maximum scour depth downstream of the V-shaped riffle. h new predictive equation for the maximum scour depth was developed using the non-dimensional hydraulic and geometrical variables. The parameters used in the proposed equations were determined using the experimental data. The analysis reveals that the scour depth is dependent dominantly on the Froude number at the opening of the V-shaped riffle, while the angle of riffle and the opening width also affect the scour depth. The proposed equation for the scour of V-shaped riffle well agrees with the experimental data. It can be used for estimating the scour of the V-shaped riffle in sandbed streams.

• Journal of Korea Water Resources Association
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• v.37 no.7
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• pp.527-540
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• 2004

In order to investigate characteristics of the primary flow and the secondary currents in the meandering channel, laboratory experiments were conducted in the meandering channel made up of alterative bends haying 120。 arc angle. Experiments were performed in two types of cross-sections, a rectangular cross-section and a curved cross-section which was made to adopt a beta probability function. Three-dimensional velocity fields were measured using a micro-ADV. As the result of experiments, in case of the rectangular cross-section, the primary flow occurred taking the shortest course, which is similar to the result of previous researches. In case of the curved cross-section, the primary flow was expected to occur along the thalweg. but it occurred almost along the shortest way. This is considered due to effects of bottom roughness and sinuosity Not only a main cell but also a secondary cell of secondary currents were clearly shown by mean of the stream function. The secondary current intensity has the maximum value near the apex of the second bend for cases of both rectangular and curved cross-sections. However, the value of the secondary current intensity for the curved section is slightly larger than that for the rectangular cross-section. Also, in case of the rectangular cross-section, the higher the ratio of width to depth is, the larger the secondary current intensity is.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.71-78
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• 2012

The habitat suitability is an important factor to estimate the distribution and size of the physical habitat in river. This suitability is also a key factor to decide the ecological flow discharge for the fish. For the ecological analysis in river, accurate values of habitat suitability index for various fishes are necessary. In general, fish habitat is affected by the physical factor of the flow depth and velocity as well as the chemical and biological factors of nutrient and attached algae. Thus, the condition of the fish habitat is expected to be changed with each watershed and tributary. In this study, the habitat suitability indices for fishes were proposed by using the field monitoring data in the rivers of the Han and Geum river watersheds. The proposed indices for three fishes are compared: Zacco platypus, Zacco temminckii, and Coreoleuciscus splendidus. The results show that Zacco platypus has a similar distribution of habitat suitability index in two watersheds. Zacco temminckii and Coreoleuciscus splendidus, however, have different distributions with watersheds. Also, for Zacco platypus, the developed indices at three tributaries of the Han river are compared: Cheng-mi stream, Dal stream, and Hong-cheon stream. The comparision shows that the index in the Cheng-mi stream is different with those in the other rivers. This is expected to be because of a high nutrient concentration at the Cheong-mi stream.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.209-214
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• 2005

수위, 우량, 유량, 유사량 등 수문자료중에서 유량자료는 가장 많은 쓰임새를 갖고 있음에도 불구하고 신뢰도가 낮은 이유로 인해 많은 문제점을 안고 있는 것이 현실이다. 이렇게 유량측정자료의 신뢰도가 낮은 이유는 크게 5가지로 들 수 있는데 1)측정 수행자의 잦은 교체 등에 따른 조사역량 부족, 2)수행자별 유량측정 및 분석방법 상이, 3)장비의 유속검정 등 관리미흡 및 성능 저하, 4)유량측정 상당시간 경과후 유량측정성과 정리로 오류 수정 곤란, 5)유량측정성과의 체계적인 관리 미흡 등이다. 이러한 문제점을 개선하고 현장에서의 유량측정 신뢰도를 향상시키기 위하여 (주)웹솔루스에서는 한국수자원공사의 용역을 통해 현장의 유량 측정 결과를 PDA를 이용하여 기록하고 이를 실시간으로 중앙의 서버로 전송하여 과거 자료의 분석을 통해 측정자료의 신뢰도를 검증함으로써 신뢰성 있는 유량측정자료를 측정하도록 지원하는 유량측정 신뢰도 향상 시스템을 개발하였고, 한국수자원공사와 공동으로 두개의 특허출원을 하였다(특허출원: 10-2002-0049188, 10-2005-11550). 현재 이 시스템은 2002년 8월 착수를 시작으로 9개월이 지난 2003년 3월에 시험판의 개발을 완료하고, 용담댐 유역의 주천교 등 5개 지점에 시험 적용하면서 많은 개선과 보완을 거쳐 2005년 현재에는 한국수자원공사에서 운영하고 있는 13개의 댐과 1개의 국가하천에 대하여 총 59개의 관측지점에서 활용되고 있으며, 현재(2005. 2월 기준)까지 1,660여건 이상의 전자야장이 데이터베이스에 구축되었으며, 유량측정성과 DB는 웹시스템(http://river.kowaco.or.kr)을 통해 운영되고 있다. 본 시스템 도입을 통해 유량측정성과가 체계적으로 관리되고 있으며, 향후 시스템에 대한 지속적인 유지관리가 이루어진다면 오랜기간에 걸쳐 축적된 많은 양의 유량자료는 수자원관리에 큰 역할을 수행할 수 있을것으로 판단된다. 개발계획 및 유역의 특성 등을 조사하고, 시험유역의 선정기준을 수립하여 연구의 목적과 부합되는 지구를 시험유역으로 선정하였으며 선정된 시험유역에 대하여 수문$\cdot$수질 조사 계획을 수립하고, 계측시설을 설치하여 시험운영을 실시하고, 향후 시험유역의 수문계측 및 관리방안을 수립하고자 한다.1종이었다. 이 중 한국 고유종은 11종이었고, 외래 어종은 검정우럭과 2종이 조사되었으며, Zacco platypus(피라미), Zacco temmincki(갈겨니), Acheilongnathus koreanus(칼납자루), Odontobutis platycephala(동사리), Coreoleuciscus splendidus(쉬리) 순으로 분포하고 있었고, Acheilognathus signifer(묵납자루)는 댐 건설 전에는 많이 분포하였으나 현장조사에서 서식을 확인 할 수 언어 개체수의 큰 감소내지 멸종된 것으로 추정되었다.에서 동시에 시행하였다. 수술 후 1년 내 시행한 심초음파에서 모든 환아에서 단지 경등도 이하의 승모판 폐쇄 부전 소견을 보였다. 수술 후 조기 사망은 없었으며, 합병증으로는 유미흉이 한 명에서 있었다. 술 후 10개월째 허혈성 확장성 심근증이 호전되지 않아 Dor 술식을 시행한 후 사망한 예를 제외한 나머지 6명은 특이 증상 없이 정상 생활 중이다 결론: 좌관상동맥 페동맥이상 기시증은 드물기는 하나, 영유아기에 심근경색 및 허혈성 심근증 또는 선천성 승모판 폐쇄 부전등을 초래하는 심각한 선천성 심질환이다. 그러나 진단 즉시 직접 좌관상동맥-대동맥 이식술로 수술적 교정을 해줌으로써 좋은 성적을 기대할 수 있음을 보여주었다.특히 교사들이 중요하게 인식하는 해방적 행동에 대한 목표를 강조하여 적용할 필요가 있음을 시사하고 있다.교하여 유의한 차이가 관찰되지 않았다. 또한 HSP 환자군에서도 $IL1RN^{*}2$ allele 빈도와 carria

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.302-307
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• 2009

물리적인 조류제어 기술에 해당하는 수류 차단막(이후 차단막)은 유입하천의 수류를 차단 또는 우회시켜 영양염류가 저수지의 유광층으로 공급되는 것을 차단하고 본류 수역으로의 조류 확산을 방지하는 기능이 있어 일본에서는 저수지 녹조제어 대책으로 자주 활용된 바 있다. 그러나 이러한 차단막은 국내 저수지와 같이 홍수시 유입 유속이 크고 수위변동이 심한 환경에서는 설치효과가 검증되지 않아 현장적용에 앞서 수치모의를 통한 효과 검증이 선행되어야 하며, 최적 규모와 위치 선정도 필요하다. 본 연구에서는 수위변동이 심한 국내 저수지 특성을 고려하여 차단막이 수위변화에 따라 상하로 이동할 수 있도록 기존 CE-QUAL-W2(이후W2) 모델의 알고리즘을 수정하고, 대청호에서 다양한 수리 수문조건에서 차단막의 기작과 효과를 예측하기 위해 가뭄년(2001년)과 평수년(2004, 2006년)을 대상으로 각각 모델을 적용하였다. 차단막 설치 예정지점은 소옥천 하류(7 m 깊이)와 댐으로부터 각각 14.9 km, 27.4 km 상류에 위치한 회남대교 아래 지점(10 m 깊이)과 대정리(10 m 깊이)로 가정하고, 모의 시나리오는 차단막을 설치하지 않은 경우(S-1), 소옥천 하류에 단독으로 설치한 경우(S-2), 소옥천과 대정리에 설치한 경우(S-3), 모든 지점에 설치한 경우(S-4)를 비교하였다. 차단막 설치에 따른 수문년 및 계절별 수질개선 효과(S-1에 대한 S-4 농도 저감 비)를 비교한 결과, 대청호에서 녹조문제가 가장 심각했던 2001년 6월$^{\sim}$8월 기간 동안 차단막은 봄-여름에 걸쳐 모든 비교 지점(회남, 댐, 추동, 문의수역)에서 Chl-a 농도를 최저(문의수역) 30%에서 최고(회남수역) 70% 정도 저감하는 효과를나타냈다. 평수년인 2004년과 2006년에는 강우사상에 따라 차단막 설치에 따른 Chl-a의 농도 저감 효과가 지점별로 다르게 나타났으며, 큰 강우사상이 6월, 7월, 8월에 걸쳐 골고루 발생한 2004년에 비해 7월 한 달 동안 집중된 2006년에 설치효과가 크게 나타났다. 수역별로 차단막의 설치효과를 비교해 보면, 유입수의 영향을 직접 받는 회남수역과 추동수역이 댐 앞과 문의수역에 비해 차단막 설치에 따른 Chl-a 농도의 저감 효과가 큰 것으로 나타났다. 그러나, 큰 홍수가 유입할 때 차단막 상류부에 집적된 조류의 일부가 수류의 포획(Entrainment) 기작에 의해 저수지 내부로 유입되는 것으로 확인되어 차단막 효과를 극대화하기 위해서는 홍수 전 차단막 상류부에 집적된 조류의 처리대책이 필요할 것으로 판단된다.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.492-506
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• 2013

The historical accounts and materials about the eruption of Mt. Baekdusan as observed by the geological survey is now showing some signs of waking from a long slumber. As a response of the volcanic eruption of Mt. Baekdusan, water release may occur from the stored water in Lake Cheonjii caldera. The volcanic flood is crucial in that it has huge potential energy that can destruct all kinds of man-made structures and that its velocity can reach up to 100 km $hr^{-1}$ to cover hundreds of kilometers of downstream of Lake Cheonji. The ultimate goal of the study is to estimate the level of damage caused by the volcanic flood of Lake Cheon-Ji caldera. As a preliminary study a scenario-based numerical analysis is performed to build hydrographs as a function of time. The analysis is performed for each scenario (breach, magma uplift, combination of uplift and breach, formation of precipitation etc.) and the parameters to require a model structure is chosen on the basis of the historic records of other volcanos. This study only considers the amount of water at the rim site as a function of time for the estimation whereas the downstream routing process is not considered in this study.