• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.6
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• pp.549-556
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• 1984

Forty-eight fish species belonging to 38 genera and 10 families were collected along the Dongjin River from July 1982 to May 1984. The dominant species of them were Rhinogobius brunneus and Zacco platypus in the main stream and Abbottina springeri, Hemiculter eigenmanni and Moroco oxycephalus in the tributaries respectively. It was remarkable point in the distributional study of freshwater-fishes of Korea that both species of Pelteobagrus nitidus and Lefua costata were observed in the present studied areas for the first time. It was found that 6 species of Hypomesus olidus, Hemiculter eigenmanni, Pseudobagrus sp., Liobagrus mediadiposalis, Cobitis taenia striata, and Lepomis macrochirus inhabiting the seomjin River were unstably incorporated into the fish communities at the upper reaches of the Dongjin River which the Seomjin River flow down for the water power generation. It is suggested that the integradation between two subspecies of C. taenia occurs at the intermediate water areas in the mainstream of the Dongjin River, whereas C. t. striate is remained only at the upper reaches and C. t. lutheri is lived in the lower parts of the river. Population of C. koreensis found in the mainstream was exhibited considerable differences in the color patterns on the body sides of them in comparison with other populations, which was discussed in relation to the habitat variations adapted to the confluent condition of joining the Seomjin stream with the Dongjin River.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.86-96
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• 2002

The distributions of suspended particulate matter (SPM), chlorophyll a, particulate organic carbon (POC) and nitrogen (PON) and particulate biogenic silica (PBSi) along the salinity gradient were investigated in the Seomjin River estuary from March 1999 to April 2001. Sampling sites were set based on the surface salinity during each cruise rather than geographic locations. Concentrations of SPM were less than 20 mg/L, suggesting relatively low input of terrestrial SPM despite large freshwater discharge through Seomiin River, Chlorophyll a peaks occurred at 5$\~$ 15 psu salinity zone (10$\~$20 km from Nan Cho Island) in November 1999, at 15$\~$25 psu (10$\~$20 km) salinity zone in April 2000 and at 1$\~$15 psu salinity zone (15$\~$20 km) in October 2000 (ca. 8$\~$58%\mu$g/L). Concentrations of POC, PON and PBSi were also high at the same zone. Relatively low ratios of POC to chlorophyll a in mid-salinity zone where POM peak occurred suggests high contribution of living phytoplankton to the total POC. On the other hand, relatively high ratios of POC to chlorophyll $\alpha$ in very low salinity zone and the mouth of estuary indicated relatively high portions of detrital POC. Consequently, the low concentrations of SPM in this estuary and the high concentrations of chlorophyll $\alpha$ and the low ratios of POC to chlorophyll $\alpha$ in the mid-salinity zone suggest that production of living phytoplankton is primary factor in controlling distribution of POM along the salinity gradients in the Seomjin River estuary.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.261-272
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• 2005

The groundwaters in the basin of Seomjin River are classified mainly into Na-Cl type with high EC and $NaHCO_3$ type with low EC, and are characterized by enriched $K^+,\;Mg^{2+},\; NO_3^-,\; and\;SO_4\;^{2-}$ contents. The epm fraction of $Na^+Cl^-$ in TDS increases in general with increasing EC of groundwater. The correlation patterns among dissolved ions indicate that $Na^+\;and\;Cl^-$ are derived mainly from intruded seawater, and $K^+,\;Mg^{2-},\;and\;SO_4\;^{2-}$ from anthropogenic source such as a chemical fertilizer. The groundwaters that exceed the recommended limits far agricultural irrigation water contains $23\%\;of\;Cl^-$ reflecting sea-water intrusion, but $50\%\;of\;NO_3^-$ as an anthropogenic pollution, among the wells investigated. In risk assessment of groundwaters by the EC-SAR relationship, only $40\%$ of the groundwaters shows the suitable quality for agricultural irrigation water without any sodium and salinity hazards. Consequently, the pollution sources that cause degradation of groundwater quality in the basin of Seomjin River are the usage of chemical fertilizers and the intrusion of seawater, resulted primarily from the extension of riverward backflow of seawater and secondarily from the overpumping of groundwater.

• Economic and Environmental Geology
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• v.42 no.2
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• pp.107-120
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• 2009

Spacial variation in organic components and temporal variation in the origin was examined through the organic geochemical (TC, TN, TS, $CaCO_3$, TOC, C/N, and $\delta^{13}C$) and pyrolysis analysis (HI, OI, and Tmax) in the core sediments which were acquired in the continental shelf of the South Sea close to Seomjin River. Levels of TC, TN, and TS show relatively low and constant in the core SJ03 located close to the Seomjin River mouth, while those are increased a little with being varied with low amplitude in the core SJ02 and SJ04 acquired at the middle of inner shelf area. They fluctuated with high amplitude in the core SJ01 and SJ05 near to the outer boundary of inner shelf. The vertical characteristics of organic components in the core SJ01 acquired at the outer boundary show that the area has undergone distinctly the environmental change at 9.0 kyr B.P. After 9.0 kyr B.P., Levels of TC, TOC, TN, $CaCO_3$, $\delta^{13}C$, HI, and Tmax are rapidly increased, while C/N and or are significantly decreased. Even though the contents of organic components are not high, such a changes reflect that the terrigenous organic matters were predominant before 9.0 kyr B.P due to the influence of Seomjin River, but after then, the marine organic matters have dominated due to the inflow of the Tshusima current.

• Korean Journal of Ecology and Environment
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• v.50 no.3
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• pp.275-285
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• 2017

To investigate the changes of dominant species of benthic macroinvertebrates according to the changes of temperature and precipitation, we surveyed twenty sites of the main Seomjin River in May and September in 2013 and 2014. The temperature, precipitation, water quality factors and substrate composition, which are important factors in benthos habitat environment, were collected and measured. The average temperature of the Seomjin River increased by $0.2^{\circ}C$ in 2014 compared to 2013, and the temperature increased from upstream to downstream, showing a difference of more than $3^{\circ}C$. Also, the annual cumulative precipitation (ACP) was increased toward low latitude. The temperature of Seomjin River increased more than twice in September ($21.7{\sim}24.5^{\circ}C$) after rainfall compared to May ($7.6{\sim}11.3^{\circ}C$) before rainfall, and CP (cumulative precipitation) increased about 3 times before rainfall (263 mm~287.5 mm) and after rainfall (756.3 mm~882 mm). Due to washing effect by summer precipitation, total number of species and individuals for benthic macroinvertebrates were higher in May than in September. Chironomidae sp. and Choroterpes altioculus were dominated in May, Ecdyonurus levis, Macrostemum radiatum and Choroterpes altioculus were dominated in September. As a result of correlation analysis between community indices and environment factors, it was found that there is a high correlation with boulder and sand among substrate compositions. According to the results of cluster analysis based on temperature, CP and the dominant species of benthic macroinvertebrates in Seomjin River, it was divided into two groups following temperature and CP, and the dominant species and geographical position were reflected and divided into detailed groups.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.3
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• pp.164-170
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• 2005

To investigate the aquatic environmental factors and processes controlling primary production in the Seomjin River estuary, chlorophyll a, nutrients, pH, SS, DO, temperature, salinity and primary productivity were measured in February, April, August and October, 2001. Primary productivity values ranged between 50.7 and 14,120.3 mg C $m^{-3} day^{-1}$ during the sampling period. In contrast to other estuaries, light condition did not seem to be the important limiting factor far primary production due to high water-column transparency during most of the time. The autumn bloom occurred in regions where salinity values ranged between 10 and 20 psu. This phenomenon appeared to develop every year and deserves further investigation. The behavior of nutrients, which is one of the major factors controlling the primary productivity, appeared to be governed by salinity regimes. The main source of nitrogenous nutrients seemed to be the freshwater runoff from the Seomjin River. However, that of phosphorus seemed to be from the industrial wastewater in Gwangyang area. The primary pro-duction of phytoplankton in the study area varied with space and time, showing a close correlation with water column transparency, and exhibited higher values compared to those of adjacent coastal regions in Gwangyang Bay.

• Korean Journal of Ecology and Environment
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• v.54 no.1
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• pp.12-23
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• 2021

As fish communities are sensitive to natural environmental changes as well as anthropogenic pressures, their composition and characteristics help us to assess the aquatic ecosystem health. The fish fauna and the length-weight relationship of Zacco platypus in the Seomjin River system were investigated from July 2018 to May 2019. The collected species during the survey period were 49 species belong to 14 families including 19 Korean endemic and two endangered species. According to Bray-Curtis similarities, 14 sites were divided into four groups based on the fish community composition; two groups(group A, B) and two uncategorized sites(group C, D). There were significant differences between groups A and B(analysis of similarities, R=0.722, p=0.002). A similarity percentage analysis revealed that Z. koreanus(8.55%), Micropterus salmoides(6.90%), and Lepomis macrochirus (4.90%) contributed to these differences of fish assemblages between group A and B. Group A showed higher relative abundances of exotic species such as M. salmoides and L. macrochirus, while Z. platypus and Z. koreanus which are the common species in Korea, were the most dominant species in group B. Based on the length-weight relationship of Z. platypus, b values were varied from 2.82 to 3.80, indicating that growth patterns of the species were spatially different. This study could be served as baseline data for understanding fish fauna, assessing habitat characteristics based on the fauna, and identifying health conditions of Z. platypus in the Seomjin River system.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.285-293
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• 2023

This study conducted to investigate the temporal and spatial variations in the fish community structure in the Seomjin River estuary (ES1~ES3) and Gwangyang Bay (ES4~ES8). Surveys were conducted at eight points between May and September from 2020 to 2021. A total of 5,111 fish were collected, representing 42 families, 68 genera, and 78 species. The dominant species collected during the survey period were Pennahia argentata, with 2,370 individuals and a relative abundance of 46.4%. Also, as a subdominant species, Nuchequula nuchalis, 1643 individuals were caught, accounting for 32.1% relative abundance. According to Bray-Curtis similarities, observations were divided into three groups based on the fish community composition, and they were further categorized into brackish water areas, coastal areas, inner areas, and outer areas. Group 1 mainly consisted of fish inhabiting freshwater and brackish water areas, while group 3 exclusively contained fish living in marine waters. ANOSIM (Analysis of Similarity) analysis revealed a significant difference (ANOSIM R=0.783, p=0.001) between Group 2 and Group 3, and the species contributing to these clusters were P. argentata and Muraenesox cinereus. The study demonstrated spatial changes in the fish community structure from the Seomjin River estuary to the outer coast. The findings highlight the importance of long-term monitoring of major species that exhibit spatial variations, serving as essential foundational data for the conservation and management of economically significant fish species.

• Journal of the Korean GEO-environmental Society
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• v.3 no.4
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• pp.11-17
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• 2002

The purpose of this study is the prediction of pollutant loads into Seomjin river watershed using neural networks model. The pollutant loads into river watershed depend upon the water quantity of inflow from the upstream as well as the water quality of the inflow into the river. For the estimation of pollutants into river, a neural networks model which has the features of multi-layered structure and parallel multi-connections is used. The used water quality parameters are BOD, COD and SS into Seomjin river. The results of calibration are satisfactory, and proved the availability of a proposed neural networks model to estimate short-term water quality pollutants into river system.