• Animal cells and systems
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• 제16권1호
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• pp.69-76
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• 2012

This study was conducted to examine how a low-head dam removal (partial removal) could affect benthic macroinvertebrate communities in a stream. Benthic macroinvertebrates and substrates were seasonally sampled before and after dam removal (March 2006-April 2007). Benthic macroinvertebrates and substrates were quantitatively sampled from immediately upstream (upper: pool) and downstream (lower: riffle) sites, the location of the dam itself (middle), and immediately above the impoundment (control: riffle). After the removal, species richness and density of benthic macroinvertebrates as well as the EPT group (Ephemeroptera, Plecoptera and Trichoptera) increased to higher levels than those before the removal, while functional feeding groups and habitat orientation groups changed more heterogeneously at the upper site. At the lower site, species richness and density decreased somewhat immediately after dam removal, which was associated with an increase of silt and sand, but recovered after monsoon floods which helped to enhance substrate diversity at the upper site. Decreased dominance index and increased diversity index in both the upper and lower sites are evidence of positive effects from the dam removal. In conclusion, we suggest that even a partial removal of a dam, resulting in increased substrate diversity in the upper site, could sufficiently help rehabilitate lost ecological integrity of streams without major habitat changes.

• 한국세라믹학회지
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• 제35권2호
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• pp.201-207
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• 1998

A tube-type filter dam(or baffle with holes) for ferrous melt refining is applied to the tundish operation for molten steel having low carbon and ultra-low carbon. The changes in the total oxygen content insoluble aluminum content and the distribution of inclusion size in molten steel during tundish operation were in-vestigated at the pouring part strand and mold of tundish. Removal mechanism of inclusions is considered to be caused by buoyancy action of the filter dam better than filtration action and the size range of in-clusions filtrated by the filter dam was for 30-50$\mu\textrm{m}$. Decrease in deviation of inclusion content in molten steel was confirmed for appling the filter dam in comparison with using conventional dam and weir. Also the filter dam had the advantage of baffle with holes at lower part in the efficiency of inclusions removal.

• 대한인간공학회지
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• 제36권5호
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• pp.559-568
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• 2017

Objective: The aim of this study is to investigate the effective managerial factors influencing dose reduction of the nozzle dam installation and removal tasks ranking within top 3 in viewpoint of average collective dose of nuclear power plant maintenance job. Background: International Commission on Radiation Protection (ICRP) recommended to reduce unnecessary dose and to minimize the necessary dose on the participants of maintenance job in radiation fields. Method: Seven sessions of nozzle dam installation and removal task logs yielded a multiple regression model with collective dose as a dependent variable and work time, number of participants, space doses before and after shield as independent variables. From the sessions in which a significant reduction in collective dose occurred, the effective managerial factors were elicited. Results: Work time was the most important factor contributing to collective dose reduction of nozzle dam installation and removal task. Introduction of new technology in nozzle dam design or maintenance job is the most important factor for work time reduction. Conclusion: With extended task logs and big data processing technique, the more accurate prediction model illustrating the relationship between collective dose reduction and effective managerial factors would be developed. Application: The effective managerial factors will be useful to reduce collective dose of decommissioning tasks as well as regular preventive maintenance tasks for a nuclear power plant.

• 한국환경복원기술학회지
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• 제11권2호
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• pp.40-54
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• 2008

Small and large dams are installed in the course of a stream for maintaining the water level of the stream or obtaining agricultural water. Currently about 18,000 of them are installed in Korea to supply water. However, the environmental problems of small dams are well known : the interruption of stream eco-corridors, deterioration of water quality in the upper reaches of the small dam, changes in the habitats of riparian organisms, damages to the stream scenery. In a very few of these small dams artificial eco-corridors like fishways are installed, but the number is very minimal.Accordingly, to efficiently restore stream eco-corridors by removing these small dams, it will be necessary to closely examine physical impacts, such as changes in the riverbed and changes in the shape of the stream caused by the removal, chemical impacts, such as changes in water quality, and transport and accumulation of contaminated sediments and biological impacts, such as changes in the habitats of organisms, and develop related technologies in advance, and have these technologies verified through demonstration application in the sites. In this study, we analyzed the physical, chemical and ecological impacts of the removal of the above-mentioned small dams, and conducted a research on the demonstration small dam removal project for a spot investigation. As a result, the small dam removal will restore the eco-corridor, there by improving the habitat of fishes and crustaceans. The number of major underwater organisms inhabiting the Gokreungcheon, such as Korean spotted sleepers, Chinese minnows, Microphysogobio yaluensis, Abbottina rivularis, stone morokos, striped shinners, long-nosed barbels, and Chinese mitten crabs, is expected to increase, and the food chain in the ecosystem will improve so that species diversity will improve as well.

• 환경정책연구
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• 제9권2호
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• pp.41-55
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• 2010

댐은 사회전반에 걸쳐 많은 편익을 제공하고 있다. 이를 위해서는 일정수준 이상의 저수용량 확보가 필수적이다. 그러나 상류의 토사 유입으로 인하여 댐의 저수용량은 줄어들고 있는 실정이다. 전 세계적으로 5조 톤의 토사가 매년 댐 뒤에 쌓이는 실정이다. 강이 여러 지역에 걸쳐 흐르는 경우 상류의 농업에서 발생하는 토사는 장시간에 걸쳐서 지속적으로 발생하기 때문에 상류 농업종사자들은 관리를 소홀히 하는 경향이 있다. 특히 토사는 댐의 저수용량을 지속적으로 줄여 궁극적으로는 댐의 경제적 가치를 소멸시키는 효과가 있다. 따라서 상류 지역의 토사저감 노력과 함께 댐의 저수용량 확보가 급선무이다. 실증분석으로 나일강 상류의 수단 농업지역과 하류의 이집트 Aswan High Dam을 분석하였다. 실증분석 결과 상류 농업부문의 토사저감 노력과 댐의 토사제거 방안이 사회전체의 경제적 편익을 극대화하는 것으로 나타났다. 동태적 최적제어이론을 이용한 유역토사관리 모형에서 댐의 경제적 편익을 포함한 사회전체의 편익은 크게는 약 1,510억 달러로 추산되었다.

• 한국수자원학회논문집
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• 제40권11호
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• pp.909-920
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• 2007

하천환경에 대한 사회적 요구에 의해 다양한 하천 복원 및 환경개선사업이 진행되고 있으므로, 이와 같은 사업의 효과를 평가할 방법론이 제공되어야 한다. PHABSIM은 하천 흐름과 관련되어 있는 수생 생물의 수리적 서식처 적합도를 평가하기 위해 제안된 방법이다. 본 연구에서는 보 철거 구간에 PHABSIM을 적용하여, 보 철거에 따른 피라미의 물리서식처 변화와 모형의 적절성을 평가하였다. 그 결과 일반적으로 보를 철거할 경우가 존치할 때보다 물리서식처가 향상된 것으로 나타났다. 그러나 유영력이 약한 산란기의 물리서식처는 보 상류의 유속이 증가되어 감소하는 것으로 나타났으며, 이에 대한 적절한 대책이 필요하다. 본 연구에 적용한 PHABSIM은 보 철거 사업을 포한한 다양한 하천사업의 평가와 필요성을 제시하는 효과적인 방법으로 활용될 수 있을 것이다.

• Water Engineering Research
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• 제6권4호
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• pp.149-159
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• 2005

With increasing recognition on conservation of endangered species in Taiwan, one of the major conservation projects is the habitat restoration of Formosan Landlocked Salmon which is major threatened by check dams in the channel for their blockading pathway to upstream and causing the problems of population isolation and close-blood mating. By creating an opening in the central dam body appropriately, partial removal dams can provide pathway for the fish for the better upstream channel habitat. Four check dams at Gau-Shan Creek were remodeled between April of 1999 and September of 2002 with information supported from model experiments under certain hydraulic condition of field environment. Based on the follow-up investigation, the channel morphology of observation sections is in stable condition and the total number of Formosan Landlocked Salmon in this creek increased promptly at the reach containing partial-removed dams.

• 환경생물
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• 제25권4호
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• pp.385-393
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• 2007

본 조사에서는 경기도 경안천의 중류에 위치한 소형보를 철거한 이후에 변화된 저서성 대형무척추동물의 군집을 조사하였다. 조사는 보가 있었던 지점의 상류와 하류, 그리고 중류 (보의 자리)에서 보의 철거 후 4회 (2004년 11월, 2005년 5월, 2006년 1월, 그리고 2006년 5월)에 걸쳐 Surber sampler (50$\times$50 cm, 망목 0.25 mm)로 정량채집을 하였다. 조사의 결과, 조사지역에서는 총 4문 5강 11목 27과 35속 46종의 저서성 대형무척추동물이 출현하였으나, 조사시기별 출현종수는 지점당 3$\sim$17종으로 차이가 컸다. 상류지점은 보의 철거 1년 이후부터 점차 여울이 형성되고, 하상물질이 다양화 되는 등 서식환경이 바뀌자 종수가 점차 증가하였고, 분류군의 조성도 점차 다양하게 바뀌었다. 우점종은 대부분 오염에 내성이 강해 도시하천에 풍부한 깔따구류(Chironomidae sp.)와 실지렁이류(Tubificidae sp.)였고, 일부 지점에서 줄날도래(H. kozhantschikovi)가 제2우점종으로 나타났다. 보의 철거 약 1년후부터 우점도지수는 낮아지고, 종다양도지수는 높아지는 경향을 나타냈다. 상류 지점에 여울이 형성되면서 줄날도래류(Hydropsychidae spp.)가 증가하자 collector-filterers의 비율이 증가하였고, 납작하루살이류 (Heptageniidae spp.) 등의 clingers, 꼬마하루살이류 (Baetidae spp.)등의 swimmers의 비율 또한 상대적으로 증가하였다. 저서성 대형무척추동물에 의한 수환경 등급을 나타내는 군오염지수(GPI)와 수환경평가지수(ESB) 모두 보의 철거 이후 상류지점에서 수환경의 개선효과를 가져온 것으로 나타났다.

• 한국물환경학회지
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• 제28권3호
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• pp.418-425
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• 2012

Dam construction in a river can change its hydrological pattern and trap sediments, which results in ecological changes in the downstream. It is a common phenomenon in the downstream of dams to have decreased sediment flow and increased periphyton. Artificial floods and sediment application are suggested as mitigation practices in order to simulate natural process of flood; transporting sediment and sloughing periphyton off. In this study the effects of artificial floods on periphyton were examined by applying sand artificially and discharging water from a dam (Yangyang Dam, Korea). The study area has been suffering from turbidity problems caused by shore erosion of the dam. The accumulation of inorganic sediments and increase of periphyton on the river bottom are the major factors of habitat deterioration in the downstream reaches. Artificial flood and artificial addition of sand was performed in summer and the effects were measured. Piles of applied sands were washed off easily by discharge and it enhanced the periphyton sloughing effect. The removal efficiency of periphyton was 50 ~ 80% within the 2 km reach from the dam. In conclusion artificial floods and sand application can be a good mitigation measure for the habitat rehabilitation after a dam construction in streams.

• 상하수도학회지
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• 제27권1호
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• pp.39-47
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• 2013

This study demonstrates the oxidative degradation of pharmaceutical compounds during ozonation of surface waters in Ulsan. Diclofenac, carbamazepine, bezafibrate, and ibuprofen were selected as surrogate pharmaceutical compounds, and ozonation experiments were performed using raw waters collected from the Sayeon Dam and the Hoeya Dam in Ulsan. Diclofenac and carbamazepine which have high reactivity with molecular ozone showed higher removal efficiencies than bezafibrate and ibuprofen during ozonation. The addition of tert-butanol, a hydroxyl radical scavenger, increased the removal efficiencies of diclofenac and carbamazepine by increasing the ozone exposure. However, the oxidation of bezafibrate and ibuprofen was inhibited by the presence of tert-butanol due to the suppression of the exposure to hydroxyl radical. The elimination of the selected pharmaceuticals could be successfully predicted by the kinetic model base on the $R_{ct}$ concept. Depending on the experimental condition, $R_{ct}$ values were determined to be $(1.54{\sim}3.32){\times}10^{-7}$ and $(1.19{\sim}3.04){\times}10^{-7}$ for the Sayeon Dam and the Hoeya Dam waters, respectively. Relatively high $R_{ct}$ values indicate that the conversion of $O_3$ into $^{\cdot}OH$ is more pronounced for surface waters in Ulsan compared to other water sources.