• Journal of the Korean Geographical Society
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• v.42 no.3 s.120
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• pp.344-354
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• 2007

Estuarine wetlands for 33 watersheds in the Han River estuary were delineated on topographic maps from the 1910s, 1970s, and 2000s. Then, these data were used to address the issue of spatial distribution and temporal variation. Watershed characteristics such as drainage density, location, watershed size, slope, and elevation were identified for each watershed to determine the relationship between watershed characteristics and spatial distribution of estuarine wetlands. The analysis of estuarine wetlands indicated that wetlands in the estuary had declined gradually between the 1910s and the 1970s, although most wetlands were lost since the 1970s mainly caused by the large development projects related to urban expansion in metropolitan Seoul. The sediment composition and formation processes of the wetlands differed with watershed location; mud flats dominate in the lower part of the estuary, and relatively more sandy and emergent-plant wetlands occur near the main channel and tributaries of the Han River. Relatively more estuary wetlands occur in large watersheds, which have high slopes and low elevations. Estuarine wetlands have been lost dramatically in the densely populated watershed regions (i.e., Han River Seoul, Han River Goyang, West Han River), while relatively more wetlands have remained in undeveloped regions, including the Lower Imjin River and Lower Han River. In particular, anthropogenic disturbance has played an important role in the loss of wetland through the conversion of wetland into agricultural and developed land.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.32-40
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• 2006

The Ichthyofauna and fish community were studied in the lower course of Imjin River from April 2003 to October 2004. During the survey period 80 species belonging to 23 families were collected. Twenty-five species (31.1%) of them were Korean endemic species. Exotic fishes were Carassius cuvieri, Lepomis macrochirus and Micropterus salmoides, and they complied 1.3% of total catch. The species of Hemibarbus mylodon was identified as natural monument, and acheilognathus signifer, Pseudopungtungia tenuicorpa, Gobiobotia macrocephala and Gobiobotia brevibarba were endangered species. Migration fish were Coilia ectens, Anguilla japonica, Plecoglossus altivelis and Takifugu obscurus. Dominant species were Zacco platypus (St. 1), Microphysogobio yaluensis (St. 2), Hemibarbus labeo (St. 3, 4) and coilia ectens (St. 5). The lower course of Imjin River was more abundance of species, high diversity and richness, and lower dominance index than those of the lower course of Han River.

• Journal of Korean Society on Water Environment
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• v.35 no.2
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• pp.99-104
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• 2019

The objective of this study was to investigate the relationship between the biomass of cyanobacteria and the concentration of 2-methylisoborneol (2-MIB) in the lower Gongji stream. The investigation was done using a field study that was conducted from 2015 to 2017. The 2-MIB concentration in the lower Gongji stream ranged from 0 to 153 ng/L, while the upper stream had 0 2-MIB concentration. 3 genera (Oscillatoria, Phormidium, Pseudanabaena) of cyanobacteria were detected in the lower Gongji stream with 2-MIB concentration. Among these 3 genera, an increase in Phormidium, Pseudanabaena biomass was associated with an increase in 2-MIB concentration. Accordingly, Phormidium, Pseudanabaena were regarded as the biological source of 2-MIB in that area. In October 2017, although planktonic cyanobacteria occurred less frequently, many benthic cyanobacteria mats were observed on the surface of the water body. Therefore, the high 2-MIB concentration, which exceeded 110 ng/L, can likely be attributed to the benthic cyanobacteria. In a laboratory experiment, individual Oscillatoria filaments were aggregated to form a colony with a higher density. This colony tended to float on the water surface. Cyanobacteria mats after floating aggregated mats were distributed in a net shape on the bottom.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.6
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• pp.152-161
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• 2006

This study is the primary study for analyzing the classifying characteristics of river wetlands in Korea and China. It is the first step for constructing the wetlands inventories and establishing the wetland conservation strategies in North-Eastern Asia. The case study sites are Han-river which is the representative river of Korea and Tu-men river which is flowing on the borderline of 3 nations, China, North Korea and Russia. The results are as follows : 1. The types of wetlands of Han-river in Korea and Tumen-river in China were classified by the methods of Koo(2002) which is focused on the topography and hydrology and Zhu(2002) which is emphasized the vegetation and habitats. 2. There are three features which are hydrology, topography and soil cover, and vegetation to classify the wetlands into each types. 3. According to the two wetland types by Koo and Zhu, classification system, wetlands in the case study area(Han river and Duman river) were classified by types. 4. In Koo's classifying system(2002), lots of Riverine, Lacustrins and Flat wetlands are found because the topographical and hydrological features are emphasized. On the contrary in Zhu's system(2002), there are lots of Palustrine wetlands because of emphasizing the vegetation. 5. By the topographic and geological characteristics of each sites, there are more wetland types in the lower Tumen river.

• Journal of Environmental Health Sciences
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• v.10 no.2
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• pp.9-40
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• 1984

This thesis purports to overview the diverse administrative and organizational factors and plannings developed by the government organizations, municipal or otherwise, to tackle the Han River water pollution issues in the past years. This thesis also looks into the ever-worsening Han River water pollution problems, in particular, in terms of the various government plans ostensibly designed to reduce the pollution level but with little success. Also dealt with are the efficiencies with which the laws and decrees on water pollution the administrative organizations put to use in the prosecution of the diverse antiwater pollution projects involving the Han River basin. From the early 1960's up to the 1970's the government had concentrated on the growth-oriented economic policy with the result that little attention had been paid to the water pollution and other environmental issues that are bound to arise from the massive economic growth. Belatedly, the five-year Hah River Development Project was initiated in 1982 with emphasis on reducing the water pollution level at Hah River to the minimum. The following are the gists of the thesis and recommendations for the future antiwater pollution plans by the administrative organizations: 1. Documents to date indicate that the irrigation projects along the Han River area had been the main focus of attention during the Yi Dynasty and under the Japanese rule of the country. 2. Despite that the water pollution issue became the subject of many debates among the academic and research institutions in the 1960's and in the 1970's, the administrative organizations in charge of the Han River water quality control failed to come up with a concrete plan for the river's water quality control. 3. Nevertheless, the water pollution of the Han River area in fact began in the 1950's, with the unprecedented concentration into Seoul of population and the industrial facilities on a larger scale, in particular, enforced by the government's strong growthoriented policy in its Economic Development plans in the 1960's. 4. Starting in the 1960's, the Han River water pollution level dramatically increased, but the government was reluctant to promulgate or put into effect strong measures to curb the many factors contributing to the river water pollution, thus worsening the environmental issues along the Han River basin. 5. The environmental protection law and other laws and decrees relating to the antiwater and air pollution issues that were subsequently put into effect underwent so many changes that efficient anti-water pollution policies could not be effected for the Han River basin. The frequent organizational reshuffle within the administrative units concerned with environmental problems has resulted in the undue waste in personnel management and finance. 6. The administration on the environmental protection could not be efficiently carried out due to the organizational overlapping. Under the existing law, frequent organizational frictions and inefficiency are bound to occur among the central government offices themselves, as well as between the central government and the Seoul city administration, and among the city's administrative offices over the conservation of the Han River basin and over the river's anti-water pollution issue. 7. In the planning and prosecution of the Han River project, political influences from the president down to the lower-level politicious appear to have been involved. These political influences in the past had certainly had negative influence on the project, nevertheless, it appears that in the recent years, these political influences are not all that negative in view of the fact that they serve as a positive contributing factor in developing a better water quality control project along the Han River basin. The following are a few recommendations based on the data from the thesis: First, officials in charge of the Han River water quality control should pay attention to a careful screening of the opinions and recommendations from the academic circles and from the public should be made so that the government could better grasp the core issues in the environmental problems that require preventive and other necessary measures. Second, vigorous redistribution policies of population and industrial facilities away from the Seoul area should be pursued. Third, the government should refrain from revising or revamping too frequently the laws and decrees on the anti-water pollution, which is feared to cause undue inconveniences in the environmental administration. Fourth, a large-scale streamlining should be made to the existing administrative organization in an effort to do away with the inter- and intra-organizational friction. It is recommended that a secretariat for the Hah River basis conservation be established. Fifth, High-level administrative officials, with a thorough knowledge and vision on the Han River water quality control, should be prepared to better deal with the budgeting and personnel management for the Han River water pollution control not only at the control government, but also at the Seoul city municipal government levels. Environmental issues should be kept distinct from political issues. Environmental issues should not serve as a window-dressing for sheer political purposes. Sixth, the Hah River proiect should also include, along with the main Han River basin, those areas covering North Han River, South Han River, and the tributaries to the main river basin. The 'Han River Basin Water Quality Control Board' should be established immediately as a means of strengthening the current Han River basin water quality control policy. Seventh, in drawing up the Han River proiect, the administrative officials should be aware that Han River basin is a life line for those people in the region, providing them with not only a sheer physical space, but with a psychological living space for their everyday life.

• Journal of Ecology and Environment
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• v.32 no.4
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• pp.221-227
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• 2009

This study describes time lag responses between hydrological variables and phytoplankton biomass in a regulated river system, the lower Nakdong River in South Korea. The lower Nakdong is a typical flow-controlled lotic system, and its limnological characteristics are influenced by climatic variation such as monsoons and summer typhoons. Mean rainfall in the area during summer is about 1,200 mm, which comprises >60% of annual rainfall. Our results show that the regulation of flow in the Nakdong by multi-purpose dams from 1995 to 2004 affected phytoplankton dynamics. Diatom blooms occurred in winter, when the limited discharge allowed for proliferation of the phytoplankton community. Using multiple regression analysis, we detected significant time-delayed relationships between hydrological variables and phytoplankton biomass. These results may be useful for water resource managers, and suggest that 'smart flow' control would improve water quality in large regulated river systems of the Republic of Korea.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.501-508
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• 2013

We have researched heterogeneity of naturalized river plant community by ${\beta}$-diversity for restoration of river community which has high diversity plant species. As a result the average of heterogeneity was 0.32(range 0.23~0.37) from the river to the inland. This value shows community turnover of species composition of plant communities 6 times. The ${\beta}$-diversity was no difference among water system of Seomjin river, Han river, Nakdong river and Geum river. The upper-river valley(0.36) was higher than lower-river valley(0.23) in each water system(p level<0.05). Multiple regressing analysis was used for look the relationship with Environmental factors as a result, it shows ${\beta}$-diversity significant on a slope. River mimetic diagram with dominant species that appear through Belt-transect painted. Dominant plant species turned 6 time in upper-river and turned about 5 time in lower-river. The result of this study suggested practical basis of planting species and planting pattern. To improve species diversity of river plant community, slope degree raise is the most important.

• ALGAE
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• v.18 no.4
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• pp.255-262
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• 2003

Ecological characteristics of phytoplankton communities were investigated biweekly at 6 stations from Feb. 2001 to Feb. 2002 at the lower part of the Han River. During the study, a total of 267 taxa which were composed of 114 green algae, 104 diatoms, 22 blue-green algae, 13 chrysophytes and 2 dinoflagellates were observed. The standing crops of phytoplankton communities were ranged from 1.30 ${\times}10^6$ cells ${\cdot}l^{-1}$ to 37.47 ${\times}10^6$ cells ${\cdot}l^{-1}$. The dominant species were 11 taxa including Pediastrum duplex, Scenedesmus quadricauda in green algae, Osillatoria limosa, Microcystis aeruginosa, Merisomorpedia sp., Phormidium sp. in blue-green algae, and Asterionella gracillima, Aulacoseira granulata, Fragilaria crotonensis, Stephanodiscus hantzschii f. tenuis, Synedra acus in diatoms. Asterionella gracillima and Stephanodiscus hantzschii f. tenuis were abundant at every station from winter to spring. Stephanodiscus hantzschii f. tenuis occupied the highest dominant ratio and standing crop. From summer to autumn, dominant species were Aulacoseira granulata at all stations and blue-green algae such as Osillatoria limosa, Microcystis aeruginosa, Merisomorpedia sp. at some stations. These 4 species were mostly present at the lower stations 4, 5, 6 and very few at the upper stations 1, 2, 3.

• The Journal of Natural Sciences
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• v.11 no.1
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• pp.75-84
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• 1999

Benthic macroinvertebrate fauna in lower part of Han river was surveyed using ponar grab and basket sampler during May, 1995 through June, 1996.The benthic macroinvertebrates composed of 14 species, 12 families, eight orders, seven classes in three phyla. Three species of annelids, four species of molluscans, and seven species of arthropodes were collected. Annelids were collected from all sampling stations, Neanthes japonica was a dominant species. Biomass reached pick at station 4 and decreased in lower part. Biomass was so unstable that seasonal fluctuation of biomass could observed.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.810-814
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• 2009

Two dimensional steady and unsteady numerical models are applied to bend reaches of the Lower Han River and the superelevation at the Ichon-Banpo bend area of Han River was observed. The flow characteristics in the meandering river are complicated due to the effects of the centrifugal force. The centrifugal force makes the outside water surface level increase and the outside velocity decrease. To study this complex flow studying two dimensional flow is important and useful to design flood control countermeasures, the analysis of sedimentation and the site selection of intake structures. Especially, the superelevation between inside and outside of the bend should be considered to determine the height of embankment. In this study, the water surface elevations in both bank sides of the bend were measured in two reaches during floods in 2007 and 2008. And then the two-dimensional simulation using RMA-2 model was carried out. The upstream and downstream boundary conditions on bend reaches were determined by FLDWAV which is one-dimensional unsteady model. Finally, the observed data are compared with simulation results and the results of the several superelevation formulas, and the flow characteristics of the bend are discussed.