• Proceedings of the KSRS Conference
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• v.2
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• pp.856-859
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• 2006

In river with bar, the characteristics of its physical conditions have a close relationship with bar morphology. In this paper, a monitoring approach of bar transformation in the Han River Estuary is presented using RADARSAT/SAR Images. The estuary is divided into North and South Korea and its area is blocked by CCL(Civil Control Line). Satellite remote sensing, therefore, is uniquely suited to monitoring bar transformation. Based on SAR signatures for bars, bar transformation is investigated from 2000 to 2005, and monitoring of suspended-silt transportations from terrestrial runoff is tried to understand the morphology during the events of severe rain storm. SAR data did not reveal clearly the bar locations because of most of data acquisitions during high tides from 6.8 m to 9.0 m. Even though the problem, it could be said that in the estuary vegetated area and natural levees are developed well, but bars and shifted after an event like a flood. It is also showed that suspended solids such as silt transported through the estuary could contribute highly to a sedimentation environment around Incheon.

• Analytical Science and Technology
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• v.29 no.6
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• pp.293-299
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• 2016

$^{137}Cs$ was investigated in river bottom sediments located in South-Han River basin and it was compared with international case studies to estimate the concentration level of $^{137}Cs$ in river sediment of Korea. The obtained values of $^{137}Cs$ which was analyzed by gamma-ray spectrometry were in the range of <$MDA{\sim}3.80{\pm}0.14Bq/kg{\cdot}dry$ and similar to the $^{137}Cs$ activities in soil of Korea. According to international case studies, $^{137}Cs$ activities were between 3.7 to $15,396Bq/kg{\cdot}dry$, when pollutants such as nuclear power plant accidents and radiation leaks were present near the rivers. The $^{137}Cs$ activities showed a variety of distribution depending on the country, when pollution occurs and survey time. Also, $^{137}Cs$ activities of river sediments without pollution sources were mostly less than $10Bq/kg{\cdot}dry$ in other countries. It was comparable with the obtained $^{137}Cs$ activities in this study. The obtained values provide useful information on the background concentration of $^{137}Cs$ in river sediment and will be able to use a basis for determining contamination of $^{137}Cs$ in the river.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.951-963
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• 2009

The community structure and ecological characteristics of fish community in Lake Paldang were investigated from May to September 2008. During the survey period, 53 species belonging to 13 families were collected. Dominant species was Squalidus japonicus coreanus representing 81.8% of total number and 25.7% of total biomass of collected fish and subdominant species was Lepomis macrochirus representing 3.3% of total number and 18.9% of total biomass of collected fish. There were 20 Korean endemic species (38% of collected species number) including Cottus koreanus and 4 exotic species (7.5%) including Micropterus salmoides. The similarity analysis of fish communities among water areas of Lake Paldang using UPGMA showed that fish community of North-Han River was similar to that of South-Han River area and was different from that of Gyeongan River area. Long-term variation of fish community from 1972 to present study in Lake Paldang showed decrease of the species numbers after dam construction until 1994, and gradual increase from 1996 to present study indicating the disturbance of lentic system by dam construction in the 1980s. The increase of species number in the late 2000s may results in part from the increase of survey sites of successive studies. L. macrochirus which was designated as a domestic ecosystem-disturbing alien species with wide food niche have shown more than 20% of relative abundance since 1996 indicating the adverse effect on not only fish community but also aquatic ecosystem food web of Lake Paldang.

• Journal of Species Research
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• v.9 no.2
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• pp.77-84
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• 2020

As a part of the research project "Survey of freshwater organisms and specimen collection," freshwater samples were collected from the Nakdong River. Among the bacterial isolates, we selected strains that showed higher than 98.7% 16S rRNA gene sequence similarity with confirmed bacterial species previously unreported in South Korea. The 14 new records to South Korea were phylogenetically diverse and belonged to four phyla, six classes, 11 orders, and 14 genera. At the genus level, these species were found to be affiliated with Reyranella, Ferrovibrio, Brevundimonas, and Aquidulcibacter of the class Alphaproteobacteria; Pseudomonas, Cellvibrio, and Photobacterium of the class Gammaproteobacteria; Paenibacillus and Bacillus of the phylum Firmicutes; Chryseobacterium, Flavobacterium, Pedobacter of the phylum Bacteroidetes; and Actinomadura and Leifsonia of the phylum Actinobacteria. These species were further characterized by examining their Gram reaction, colony and cell morphologies, biochemical properties, and phylogenetic positions. The detailed descriptions of these 14 previously unreported species are provided.

• Journal of Korea Water Resources Association
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• v.44 no.4
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• pp.315-325
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• 2011

There are not many practical measures to solve a water conflict, when a hydromorphologically asymmetric situation in international rivers exists whereby downstream users may not affect upstream users but upstream users do cause downstream impacts. In taking advantage of this merit, North Korea has built Imnam Dam in upstream of North Han River and uses water for trans-basin hydropower generation. As an impact of this dam South Korean' area as a downstream user has been suffered from water deficit and dry river. It is very critical for South Korea to solve a key problem such as water allocation for water supply and river maintenance. Therefore, this study is aim to suggest alternatives for equitable water allocation in consideration of special circumstances between the South and the North. For this, reviewing the allocation methods of water rights is carried using lessons obtained from international river cases. The results show that the minimum desired streamflow is calculated at 7.3 $m^3/sec$; water budget analysis by the equitable distribution of streamflows at the border line of the North Han River, the difference in water supply deficiency is at 3.7 $m^3/sec$ before and after Imnam Dam; in the determined distribution method, the difference in water deficiency is at 11.38 $m^3/sec$. These results show that South Korea should be secured 11.38 $m^3/sec$ from North Korean's Imnam Dam in respective of water use right and sound river maintenance.

• Journal of Korean Society on Water Environment
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• v.33 no.3
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• pp.282-290
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• 2017

A long-term resuspension of small particles, called persistent turbidity, is one of the most important water quality concerns in the dam reservoirs system located in North Han River. Persistent turbidity may incur aesthetic nuisance and harmful effect on the ecosystem health, in addition to elevated water treatment costs for the drinking water supply to the Seoul metropolitan area. These sufferings have been more intensified as the strength and frequency of rainfall events increase by climate change in the basin. This study was to analyze the effect of an extreme turbidity flow event that occurred in 2006 on the serial reservoirs system (Soyang-Uiam-Cheongpyung-Paldang) in North Han River. The CE-QUAL-W2 model was set up and calibrated for the river and reservoirs system using the field data obtained in 2006 and 2007. The results showed that Soyang Reservoir released turbid water, which was classified as the TSS concentration is greater than 25 mg/L, for 334 days with peak TSS of 264.1 mg/L after the extreme flood event (592.7 mm) occurred between July 10 and 18 of 2006. The turbid water departed from Soyang Reservoir reached at the most downstream Paldang Reservoir after about 20 days and sustained for 41 days, which was validated with water treatment plant data. Since the released water from Soyang Reservoir had low water temperature and high TSS, an underflow formed in the downstream reservoirs and vertically mixed at Paldang Reservoir due to dilution by the sufficient inflow from South Han River.

• Journal of Korea Water Resources Association
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• v.37 no.12
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• pp.1055-1063
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• 2004

An unsteady flow model is developed that allows variable roughness coefficient for each computational point according to its spatial position and the discharge. A step function or a power function can be used for functional relation between the discharge and the Manning's roughness coefficient. The model is applied to the reach of the South Han River between the Chungju Dam and Paldang Dam, and model parameters are estimated by optimization. Estimated parameters of both the step function model and the Power function model show that Manning's roughness coefficient decreases as the discharge increases. This tendency is more noticeable for the upstream reach of Yeoju compared to the downstream reach. It turns out that the stages calculated by the variable roughness coefficient model agree better with the observed ones than those by the conventional fixed parameter model.

• Journal of The Geomorphological Association of Korea
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• v.27 no.4
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• pp.71-88
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• 2020

This study modified the properties and boundaries of the inland wetland types through the structural edit of the National Wetland DB, and analyzed the characteristics of the different land cover by area and the entire inland wetlands of South Korea. The inland wetlands of the Gangwon Basin had a small area of waters. In addition, the ratio of natural barren was high, reflecting the characteristics of the upper reaches of the large river in the east and west part of Gangwon Province. The Geum River Basin had a high percentage of aggregate land due to the development of large alluvial land, and the ratio of artistic barren was low, so various ecosystem service of wetland elements were distributed evenly. The Nakdong River Basin had a high proportion of waters as water level in the channel rose due to the installation of 4 Major Rivers Beam, and the ratio of Natural barren was low. Moreover, the water level of the main attributes flowing into the Nakdong River drainage system was not high, so the ratio of vegetation concentration was high. The Yeongsan River Basin showed that Waters had the high proportion. And the distribution of Natural barrens represented differently according to the Yeongsan River Basin and the Seomjin River Basin. Finally, Sand and Gravels supplied to rivers during precipitation were deposited in the main stream of the Han River Basin, and the differences between the side and high side was large in the area, reflecting the characteristics of the mouth of a river, so the Natural barren of Clay was distributed.

• Journal of the Korean association of regional geographers
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• v.17 no.6
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• pp.666-678
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• 2011

This study is aimed to examine the variability of consecutive dry days in South Korea. The country is divided into six basins including Han river, Nakdong river, Geum river. Seomjin Yeongsan river, Eastern Coast area and Island area, and three extreme precipitation indices-related to dry days are analyzed at sixty weather stations. Trends of max number of consecutive dry days were unstable during 1973~2010. Variability range of max number of consecutive dry days trends in Nakdong and Seomjin Yeongsan river was larger than that in Han and Geum river. Recently, the range in Nakdong and Seomjin Yeongsan river was bigger and bigger. Maximum dry spell was observed in autumn and winter in most of riverbasins. Especially, Maximum dry spell in winter was more frequent than in other seasons in Nakdong river. Variability range of persistence dry spells was smaller than that of max number of consecutive dry days. However, the increasing trends of the Geum river and the Seomjin Yeongsan river are statistically significant in recent. In Nakdong river, difference between persistence dry spell average and persistence dry spell median was larger than any other riverbasin. It means that there is strong possibility of occurrence of long term consecutive dry days in Nakdong river.

• Journal of Korean Society on Water Environment
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• v.34 no.3
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• pp.301-307
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• 2018

This study investigated the effects of sediment removal on water quality and phytoplankton development by setting up mesocosms at Uiam Lake, South Korea, and analyzing the environmental parameters and phytoplankton communities between June and October 2015. The comparison between testbed without sediment removal (TB-1) and testbed after sediment removal (TB-2) gave similar values for water temperature, pH, dissolved oxygen (DO), and electrical conductivity. Nevertheless, the average electrical conductivities of the two testbeds were $139{\mu}S/cm$ and $135{\mu}S/cm$, which were lower than the value obtained from the external control point (TB-con; $154{\mu}S/cm$). The small difference in total phosphorus (TP) and total nitrogen (TN) concentrations between the two testbeds implied that sediment removal did not greatly reduce nutrients; however, the phytoplankton cell count had decreased by approximately 37 % in TB-2 (average 1,663 cells/mL) compared to TB-1 (average 2,625 cells/mL). Compared to TB-con, the phosphorus and nitrogen concentrations of the two testbeds had decreased by 39 % and 30 %, respectively, whereas the phytoplankton abundance had decreased by up to 73 %, perhaps because of the blocked inflow of nutrients and the stabilized body of water caused by the installation of the mesocosm. The concentration of geosmin was lower in testbeds than in the external point, because installation of the structures had reduced the cyanobacteria biomass.