• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.835-843
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• 2008

In Korea, riverbank filtration has drawn attention since 1990's as an alternative having potential to stably meet the ever-increasing water demand. Some cities located in the Nak-dong River Basin are currently supplying water through riverbank filtration. This research is on the application of riverbank filtration for stable water quality in Seoul. For this purpose, we have evaluated developable amount of water with riverbank filtration for the Han River. This paper focuses on the Kwangnaru site, which was selected through a systematic analysis in the companion paper. We have conducted groundwater modeling for a proposed system of wells and an artificial lake. In the Kwangnaru district, the river length to constitute a well system was identified to be about 1,200m, due to the topography and the field condition such as ecosystem preservation zone. After many design changes, it was found that the maximum developable amount of $23.36\;million\;m^3$/year could be obtained, when 16 pumping wells were built in every 80 meters along with an artificial lake upstream.

• Journal of Korean Society on Water Environment
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• v.22 no.5
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• pp.784-795
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• 2006

The purpose of this study was to assess biological river water quality by using epilithic diatoms at 40 selected sites in Geum, Youngsan, and Seomjin River systems. The sampling and analyses were performed during three seasons including January, April and June in 2005. Various water quality parameters also were analyzed. We attempted to classify the water quality condition by epilithic diatom indices (DAIpo and TDI) with the results of corresponding analyses of various chemical water quality parameters. A five class system was delivered to describe the water quality condition ranged from "very good" to "very poor." We also proposed a way of classifying water quality condition by combining two diatom indices of DAIpo and TDI. Our results showed that biomass of epilithic diatoms varied not only seasonally but spatially; it was not likely that winter diatoms represent average water quality condition, due to high concentration of nutrients. Water quality status assessed by diatom indices was generally worse than that assessed by BOD, indicating that BOD standard likely underestimates the biological condition of the water body. Importantly, nutrient-based diatom index (TDI) generally overestimated organic matter-based index (DAIpo) at most study sites, indicating that diatoms in studied rivers were likely more affected by nutrients than organic matter. Thus, management strategy to improve river water quality in Korea is suggested to emphasize more on the nutrients than organic matters.

• Journal of Korea Water Resources Association
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• v.52 no.spc2
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• pp.835-844
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• 2019

This study dealt with a systematic approach for sediment replenishment works which defines the artificial supply of coarse sediment to downstream river channels of dams. That is an increasing practice in Japanese, American and European rivers for the purpose of compensating sediment deficits downstream and rehabilitating geomorphological habitats below dams. We introduced five main objectives of the sediment replenishment, simply from construction of artificial spawning redds for anadromous fish to restoration of fluvial geomorphological process of river system. Then we suggested determination of sediment size distribution and quantity of coarse sediment as well as selecting an effective implementation method in corresponding to specific objectives and local restrictions in the basin, reservoir and river.

• Journal of Ecology and Environment
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• v.47 no.3
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• pp.118-133
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• 2023

Background: Free-living amoebae (FLA) are widely distributed in freshwater, seawater, soil, and extreme environments, and play a critical role as feeders on diverse preys in the ecosystem. Also, some FLA can become opportunistic pathogens in animals including humans. The taxa Amoebozoa and Heterolobosea are important amoeboid groups associated with human pathogens. However, the identification and habitat of amoebae belonging to Amoebozoa and Heterolobosea remain poorly reported in the Republic of Korea. This study highlights the first record for identification and source of four amoebae including putative pathogens in the Republic of Korea. Results: In the present study, four previously reported FLA were isolated from freshwaters in Sangju Gonggeomji Reservoir (strain GO001), one of the largest reservoirs during the Joseon Dynasty period, and along the Nakdong River, the largest river in the Republic of Korea (strains NR5-2, NR12-1, and NR14-1) for the first time. Microscopic observations and 18S rDNA phylogenetic trees revealed the four isolated strains to be Acanthamoeba polyphaga (strains NR5-2 and NR12-1), Tetramitus waccamawensis (strain GO001), and Naegleria australiensis (strain NR14-1). Strains NR5-2 and NR12-1 might be the same species and belonged to the morphological Group 2 and the T4 genotype of Acanthamoeba. Strain GO001 formed a clade with T. waccamawensis in 18S rDNA phylogeny, and showed morphological characteristics similar to previously recorded strains, although the species' flagellate form was not observed. Strain NR14-1 had the typical morphology of Naegleria and formed a strongly supported clade with previously recorded strains of N. australiensis in phylogenetic analysis of 18S rDNA sequences. Conclusions: On the bases of morphological and molecular analyses, four strains of FLA were newly observed and classified in the Republic of Korea. Three strains belonging to the two species (A. polyphaga and N. australiensis) isolated from the Nakdong River have the potential to act as opportunistic pathogens that can cause fatal diseases (i.e. granulomatous amoebic encephalitis, Acanthamoeba Keratitis, and meningoencephalitis) in animals including humans. The Nakdong River in the Republic of Korea may provide a habitat for potentially pathogenic amoebae, but additional research is required to confirm the true pathogenicity of these FLA now known in the Republic of Korea.

• Journal of Wetlands Research
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• v.18 no.1
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• pp.58-67
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• 2016

This study was performed to investigate the long-term changes in water quality and benthic ecology around the Nakdong River Estuary. The effect of the estuarine barrage on the ecosystem was also evaluated. The water quality was interpreted using the field survey (2013 and 2014) and monitoring data (MOE, 1989~2013) and the macrobenthic-fauna was investigated through analysis of the field survey data (2014) and literatures review (1985~2013). The long-term variation of water quality of Nakdong River generally showed increased nutrient concentration with decreased discharge, while abrupt influence of the barrage construction was not observed. However, the nutrient and organic matter concentration inside the barrage distinctly was higher than the concentration outside the barrage because the mixing of fresh and seawater was limited by the barrage. Especially, in the period of low discharge during winter, the Chlorophyll-a concentration clearly increased more in the downstream inside the barrage, showing the barrage effect. In other words, stagnant effect caused by barrage construction had an effect on the water quality degradation in dry seasons. As for the benthic ecology inside barrage after barrage construction, molluscans and brackish-water crustaceans disappeared. Outside the barrage, benthic ecosystem has deteriorated and the small-sized organic indicative species like Prionospio membranacea, Pseudopolydora kempi, Sinocorophium sinensis became dominant due to several construction such as Myeong-Gi Bridge, Airport construction, industrial complex after the Nakdong barrage construction.

• Journal of Korea Water Resources Association
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• v.40 no.7
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• pp.503-510
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• 2007

In the area of such a nature-friendly stream improvement, it is not established yet which engineering method is suitable for stream environment, due to lack of technology. Therefore, although nature-friendly stream improvement was done with expensive engineering method, the effect has not been fully confirmed, which results from the absence of overall valuation tool of stream improvement. In this regard, it is necessary to develop and apply comprehensive and diverse valuation methods covering stream functions to the analysis of stream improvement. In this study, we collected data from years' of monitoring on the Gyeongcheon river, which is located in Sunchang-eup, Jeollabuk-do and recently underwent an nature-friendly stream improvement work. Based on the data, we developed a series of valuation methods such as stream naturalness evaluation, life cycle evaluation, amenity evaluation, and economic benefit analysis to consider the environmental function of stream from a comprehensive perspective. Stream naturalness evaluation is a quantitative analysis of how natural a stream is, and includes additional valuation items such as ecosystem and water quality for the purpose of overall valuation, unlike existing research focusing on physical elements and structural characteristics of a stream. We developed a method of stream valuation with life cycle assessment to river reorganization project. Amenity evaluation method was developed as a means to analyze residents' satisfaction with stream improvement through questionnaires. Economic benefit analysis was developed as a means to determine the attributes of environmental water supply, ecosystem, river maintenance, and water quality and predict economic benefits using contingent valuation method (CVM) and multi-attribute utility analysis (MAUA) method in order to analyze economic benefits brought in by stream improvement. It is considered that the four methods developed in this study make possible to conduct an overall and quantitative analysis of stream improvement.

• Journal of Environmental Impact Assessment
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• v.22 no.3
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• pp.241-254
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• 2013

The nutria(Myocastor coypus) that is originated from South America is a representative Invasive alien species in Korea. invasive alien species is one of the biggest causes for the loss of biodiversity and it may threaten the conservation and function of ecology as well as the welfare of mankind. Intense habitation has been made around the Nakdong River basin area that this study has analyzed the habitat density of nutria for the subject of 3 survey sites in the Nakdong River basin area. As a result of survey on habitation density in 2011 and 2012, under St.1 it was shown $2.01{\pm}0.21$/ha in 2011 and $0.69{\pm}0.55$/ha in 2012. Under St.2, it was shown $0.91{\pm}0.37$/ha in 2011 and $0.55{\pm}0.39$/ha in 2012. Under St.3, it was shown $5.31{\pm}0.72$/ha in 2011 and $3.99{\pm}2.31$/ha in 2012. The wet survey areas of St.1 and St.3 had shown relatively high habitation density compared to St. 2, the river survey area, and the average annual habitation density of the survey area was $2.74{\pm}2.29$/ha in 2011 and $1.74{\pm}1.18$/ha in 2012 that it has shown slightly reducing trend. As a result of measuring the morphology by capturing the habitation individuals, the average body length of adults is $92.23{\pm}9.41cm$, the length from the head to body for $53.90{\pm}5.15cm$, tail length for $38.33{\pm}4.83cm$, hind foot length for $13.82{\pm}1.00cm$, front foot length for $6.02{\pm}0.56cm$, and weight for $5.48{\pm}1.08kg$. As a result of comparing the types between genders, male showed a slightly higher figure in all parts compared to female and it showed significantly difference in total body length, head-body length, front foot length and total weight. As a result of analysis for each head-body length, other measured parts, weight and relativity for each measured part, all bodily part is shown to have the higher volume of correlations. The condition index of individuals in the survey area was shown in the average of $35.67{\pm}4.78$ with female for an average of $36.60{\pm}5.19$ and male for an average of $34.73{\pm}4.34$. The winter temperature in the southern area of Korea is considered for not greatly impacting on the habitation and development of nutria that, if there is no artificial control, it is considered to have certain concern of showing drastic breeding and territory expansion for the habitation group.

• Journal of Wetlands Research
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• v.16 no.3
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• pp.441-450
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• 2014

In this study, we consider ability of self-purification for a rational water quality management. And we assess the risk of Alkyl Benzene Sulfonic acid sodium salt(ABS) of harmful ingredients in Anseong Cheon watershed using QUAL2E model. The observations and simulated results were fitted well for BOD and ABS, but even though the trend of DO concentration change was well represented, the error between observation and simulation values was existed. We assessed the Risk assessment by calculating Risk quotient(RQ) by Predicted Exposure Concentration(PEC) and Predicted No-Effect Concentration(PNEC). Results of the impact of ABS on the self-purification of the river were Anseongcheon[0.0003(Bressan), 0.06(Criteria of Ministry of environment)], Jinwicheon[0.0002(Bressan), 0.04(Criteria of Ministry of environment). And result of the impact of ABS on the Aquatic ecosystem of the river were Anseongcheon[0.0667(Bressan), 0.005(Criteria of Ministry of environment)], Jinwicheon[0.1(Bressan), 0.0075(Criteria of Ministry of environment). All of these results were smaller than the 1.0 which is the reference value suggested by Norification No.30 of the National Institute of Environment Research. So, ABS did not affect a self-purification and aquatic ecosystem of the river. The method suggested in the study is a simple one and can provide more information for harmful ingredients than criteria of Ministry of environment.

• Ecology and Resilient Infrastructure
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• v.10 no.4
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• pp.171-183
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• 2023

Estuarine wetlands, which form a distinctive brackish water zone, serve as important habitats for organisms that have adapted to and thrive in this environment. Nonetheless, excessive development and utilization result in artificial disruptions that alter the distinctive functions and attributes of estuarine wetlands. To collect the basic data for the conservation of estuarine wetlands with excellent ecosystems, we investigated the vegetation distribution characteristics and biota status of the Taehwagang River Estuarine Wetland. Data from vegetation surveys have shown that 25 plant communities of six physiognomic vegetation types, including willow vegetation, lotic and lentic herbaceous vegetation, floating/submerged vegetation. In the upper reaches, where topographical diversity was high, various types of wetland vegetation were distributed. In terms of biodiversity, a total of 696 species, including 7 endangered wildlife species, were identified. Due to good ecological connectivity, tidal rivers are formed, brackish water species including various functional groups are distributed around this section. The inhabitation of various water birds, such as diving and dabbler ducks, were confirmed according to the aquatic environment of each river section. The collection of ecological information of the Taehwagang River Estuarine Wetland can be used as a framework for establishing the basis for conservation and management of the estuarine ecosystem and support policy establishment.

• Journal of environmental and Sanitary engineering
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• v.16 no.3
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• pp.22-27
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• 2001

It have been investigated how algal and bacterial symbiotic reaction influences on removal of organic carbon in river ecosystem. And artificial experimentation apparatus was made for algae'and bacteia'culture as lab scale. Investigating and researching minutely the change of concentration of organic carbon substrate and the change of population density of algae'and of bacteria'with this artificial experimentation apparatus, the next results could be obtained. 1. Successful decrease of DOC(dissolved organic carbon) could not be expected unless algal and bacterial biomass floe was nut formed effectively and unless biosorption was not proceeded effectively in the very culture system in which artificial synthetic wastewater was supplied continuously at constant rate. 2. In conditions of culture liquid of 1335 glucnse mg/L(type 1) and of 267 glucose mg:L(type 2), the algal dominant species was always Chlorella vulgaris in both types in which artificial synthetic wastewater were supplied continuously at constant rate and algae population density was around maximum 107 cells/mL. 3. It was around 108 ~ 107 cells/mL that the population density of heterotrophic bacterium. In culture medium systems type 1 and type 2 in which artificial wastewater were supplied continuously at constant rate, the same density appeared initially when using the population density of Escherichia coli w 3110 as indirect indicator. And this density decreased rapidly till the culturing date 35 days were passed away, while this density increased with gentle slope after same date and then the trend of change at type 2 was more severe than one at type 1. 4. When seeing such a change of population density of Escherichia coli w 3110, the growth of heterotrophic bacterium appeared as survival instinct pattern of broader requirement of nutrient at condition of low concentration of organic carbon substrate than condition of high concentration of same substrate.