• Journal of the Korean Society for Marine Environment & Energy
• /
• v.12 no.4
• /
• pp.248-254
• /
• 2009

Budgets of fresh water, salt, DIP and DIN in the Youngsan river estuary were estimated seasonally in order to clarify the characteristics of material cycling and flux of nutrients with a simple box model. Inflow volumes of freshwater into system was approximately $36.481{\times}10^6{\sim}663.634{\times}10^6m^3/month$ and existing water mass of freshwater in system calculated by salt budget was approximately $2.515{\times}10^6{\sim}5.812{\times}10^6m^3$. Mean residence time of freshwater was calculated to be about 0.26~2.03 day. water exchange $1,248{\times}10^6{\sim}9,489{\times}10^6m^3/month$ assumed with salinity between estuary and adjacent ocean. Inflow mass of DIN and DIN were approximately 76.63~1,149.91 ton/month and 2.91~61.22 ton/month, respectively. Residence times of DIP and DIN were calculated to be 0.45~1.10 day and 0.28~1.92 day, respectively. The ratio of water residence time versus DIP, DIN residence time was calculated that freshwater residence time was longer than DIP, DIN residence time except for summer season. Thus, We assume that circulation of Nutrients in the system will happen rapidly except for summer season. Specially DIP in Winter could assume to outer input source existence because of seawater inflow in system and high DIP concentration in open sea.

• Journal of Korea Water Resources Association
• /
• v.38 no.12 s.161
• /
• pp.1061-1072
• /
• 2005

A hydrological grey model is developed to forecast short-term river runoff from the Naju watershed located at upstream of the Youngsan estuary dam in Korea. The runoff of the Naju watershed is measured in real time at the Naju streamflow gauge station, which is a key station for forecasting the upstream inflow and operating the gates of the estuary dam in flood period. The model's governing equation is formulated on the basis of the grey system theory. The model parameters are reparameterized in combination with the grey system parameters and estimated with the annealing-simplex method In conjunction with an objective function, HMLE. To forecast accurately runoff, the fifth order differential equation was adopted as the governing equation of the model in consideration of the statistic values between the observed and forecast runoff. In calibration, RMSE values between the observed and simulated runoff of two and six Hours ahead using the model range from 3.1 to 290.5 $m^{3}/s,\;R^2$ values range from 0.909 to 0.999. In verification, RMSE values range from 26.4 to 147.4 $m^{3}/s,\;R^2$ values range from 0.940 to 0.998, compared to the observed data. In forecasting runoff in real time, the relative error values with lead-time and river stage range from -23.4 to $14.3\%$ and increase as the lead time increases. The results in this study demonstrate that the proposed model can reasonably and efficiently forecast runoff for one to six Hours ahead.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.6 no.4
• /
• pp.218-224
• /
• 2001

Water movement in the Young San River Estuary where a sea dyke was constructed, was observed using anacoustic doppler profiler (ADP) and two TGPS buoys for 25 hours on 27-28 July 2000. Hydrographic observations were simultaneously taken using CTD to understand the characteristic of the spacial structure of temperature and salinity. A large quantity of fresh water was discharged from the sea dyke on 26 July 2000. The observation period fell on neap tide. The amplitude of the tidal elevation and the maximum velocity of the tidal current were about 4 m and 12 cm/sec respectively. The water movement at the surface layer is mainly controlled by wind, and those at the other layers are controlled by semidiurnal tide. The low salinity water less than 22 psu was observed along the northern part during the early observation period while southerly wind prevails. The less saline water moves westward and finally leaves the estuary by easterly wind early on the second day. We can divide the vertical structure into four layers by hydrography and current structure. Mean velocity structure shows that relatively less saline waters at the surface and the middle layer move seaward, and the waters at the upper and the bottom layers move landward. It is thought that the intermittent discharge of river water from the sea dyke makes vertical structure of four layers.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.6
• /
• pp.735-749
• /
• 2018

In this study, one studied the principal factors and water-quality components that determine the concentration of chemical oxygen demand (COD) in seawater in estuaries, such as the Han, Geum, Youngsan, Seomjin, and Nakdong rivers in Korea. The principal factors determining the concentration of COD in seawater indicated by the principal component analysis were salinity, exogenous origin and autochthonous resources based on chlorophyll-a. Moreover, organic matter in the submarine sediment layer also had a secondary effect. Regression slope assessed the contribution of water-quality components to determine the concentration of COD in the estuary. One found that the effect of salinity on the overall survey was significant. Moreover, the effect of chlorophyll-a was also appeared in April and August. In each estuary, the most significant contribution factor was chlorophyll-a in the Nakdong River and salinity in the Han and Yongsan rivers. The contribution of salinity and chlorophyll-a were found to be the largest in the Geum River. The salinity and chlorophyll-a in the Seomjin River showed a low contribution.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.31 no.3
• /
• pp.343-352
• /
• 1998

The relationship between summer hypoxia in bottom water layer and benthic community structure was discussed at forty sampling stations in semi-enclosed Youngsan River estuarine bay, Korea. The oxygen deficient layer less than $2.0 mg/\ell$ was widely developed in the inner estuarine stations in summer due to the summer stratification. A total of 141 species was occurred, with a mean density of $1,923 ind./m^2$ and biomass of $79.44\;g/m^2$ in summer season. The species number was significantly increased with the increment of the bottom dissolved oxygen, whereas density and biomass were partially correlated within the low oxygen level of $2.0\;mg/\ell$. These results imply that benthic community structures are affected by bottom oxygen depletion in summer. Cluster analysis showed that the benthic community could be classified into three station groups. These station groups from the species composition coincided with the groups based on the environmental factors. This fact suggests that the overall spatial distribution of macrozoobenthos in Youngsan River estuarine bay in summer should be controlled by the summer hypoxia and clay content of the area. Group-I was located the innermost estunrine bay from Mokpo Harbour to near the dike, where summer hypoxia was developed and one bivalve Theora fragilis, two polychaetes, Tharyx sp. and Lumbrineris longifolia were dominated. Group-II, the central transitory area of the estuarine bay between two another stational groups, where two bivalves Theora fragilis, Raetellops pulchella and a polychaete Tharyx sp. predominated with relatively low density compared to that of Group-I. Group-III, the mouth part of the estunrine bay exposed to the open sea, where a polychaetes Poecilochaetus johnsoni and a bivalve Yoldia Johanni predominated.

• Journal of Plant Biology
• /
• v.18 no.3
• /
• pp.129-134
• /
• 1975

It was studied of relation between biomass of reed communities (Phragmitis communis) and several environmental factors concerned with such as chlor ine, pH, humus content in soil and depth of seawater submerged. Two sites where were the different geographical conditions were set up. One site had two plots: H plot, at theshallows of seawater, was not submerged except at full tide or at heavy rainfall, and M plot, at medium depth of seawater, submerged at every common tide at inside of a bank along the west seashore of Mu-An-peninsula. The other site also two plots: M' plot, at medium depth, submerged about 10 hours at each tide, and L plot, at deep seawater submerged every tims at tide at the outside of a bank along the eastside estuary of Youngsan river. Maximum standing crop of the reed community was shown on 25th of June: biomass at H M, M' and L plot were respectively 4.65, 3.60, 0.98, and 0.67 kg dry weight per $m^2$. Density of individual at H, M, M' and L plot was 67, 78, 244 and 333 plants per $m^2$. Net production of the terrestrial parts of rred community on the outside of the bank were lesser as much as a sixth than that on inside, but the density of the plant on outside of the bank was higher as much 4 or 5 times than that on inside. It was assumed that the growth of reed plant was inhibited by high chlorine, high pH, less humus in soil and submergence of seawater for long period.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.5
• /
• pp.15-20
• /
• 2008

Compressibility of the marine clay was mainly studied velocity of consolidation and numerical analysis by this time but studies of reevaluated from the field measurement data was a little. For last three years, areal fills and extensive field instrumentations including settlement and pore water pressure were performed in the site of the Youngsan River estuary site, South Korea. From the settlement data, field consolidation curves for sub-layers were reconstructed. Effective surcharge loads during the staged loadings were calculated using the fill heights and the excess pore water pressures in the ground. In the numerical analysis (PLAXIS), prefabricated vertical drains were also simulated. Laboratory, field, and numerical analysis showed good agreements in compressibility. Due to different conditions and limitations of the clay was the same range of the oedometer tests.

• The Korean Journal of Quaternary Research
• /
• v.17 no.2
• /
• pp.17-23
• /
• 2003

In Korea terrestrial fluvial sequences can be used as pedological and sedimentological markers indicating a millenium-scale environmental and climatic changes imprinted in fluvial sub-environments, which in turn are represented by the cyclicity of fluvial sands, backswamp organic muds, and flooding muds intercalations of frostcracked or dessicated brown paleosols. Post LGM and Holocene fluvial and alluvial sedimentary sequences of Korea are formed in such landscapes of coastal, floodplain, backswamp and hillslope areas. Among them, the most outstanding depositional sequences are fluvial gravels, sands and organic mud deposits in coastal, fluvial, or alluvial wetlands. The aim of this study is to explain the sedimentary sequences and palynofloral zones since the last 15,000years, on the basis of organic muds layers intercalated in fluvial sand deposits. Jangheung-ri site of Nam river, Soro-ri site of Miho river, Youngsan rivermouth site in Muan, Oksan-ri site of Hampyeong and Sanggap-ri site of Gochang are illustrated to interpret their sedimentary facies, radiocarbon datings, and palynofloral zonation. Up to the Middle to Late Last Glacial(up to 30-35Ka), old river-bed, flooding, and backswamp sequences contain such arboreal pollens as Pinus, Abies, and Picea, and rich in non-arboreal pollens like Cyperaceae, Gramineae, Ranunculaceae, and Compositae. During the LGM and post-LGM periods until Younger Dryas, vegetation has changes from the sub-alpine conifer forest(up to about 17-11Ka), through the conifer and broad-leaved deciduous forest, or mixed forest (formed during 16,680-13,010yrB.P), to the deciduous and broad-leaved forest (older than 9,500yrB.P). In the Earliest Holocene flooding deposits, fragments of plant roots are abundant and subjected to intensive pedogenic processes. During Holocene, three arboreal pollen zones are identified in the ascending order of strata； Pinus-Colyus zone(mixed conifer and deciduous broad-leaved forest, about up to 10Ka), Alnus-Quercus forest (the cool temperate deciduous broad-leaved forest, about 10Ka-2Ka), and Pinus forest (the conifer forest, about after 2Ka), as examplified in Soro-ri site of Cheonwon county. The palynological zonations of Soro-ri, Oksan-ri, Sanggap-ri, Youngsan estuary, and Gimhae fluvial plain have been recognized as a provisional correlation tool, and zonations based on fluvial backswamp and flooding deposits shows a similar result with those of previous researchers.

• Proceedings of KOSOMES biannual meeting
• /
• 2009.06a
• /
• pp.149-150
• /
• 2009

영산강 하구둑에 의해 폐쇄내만의 조건을 가진 영산강 하구역에서 식물플랑크톤의 계절변동을 파악하고자 2008년에 계절별로 7개 정점에서 조사하였다. 영산강 하구역에서 출현한 식물플랑크톤 개체수는 14$\sim$34,958cells/mL의 범위를 보였다. 조사시기별로는 7월에 평균 10,796cells/mL가 출현하여 조사기간 중 가장 많은 출현 개체수를 보였고, 이어서 9월(평균 3,327cells/mL), 5월(평균 590cells/mL), 11월(평균 34cells/mL) 순으로 감소하여 조사시기별 출현개체수의 변동이 매우 심하였다. 규조류는 모든 조사시기에 걸쳐 최고의 점유율을 나타내었고 11월을 제외하면 전체 개체수의 90%이상을 차지하고 있어 규조류가 영산강 하구역의 식물플랑크톤 생물량을 좌우하고 있는 종임을 알 수 있었다. 영산강 하구역에서 출현한 식물플랑크톤의 제 1 우점종은 5월에 Eucampia zodiacus(83.1%), 7월에 Chaetoceros curvisetus(24.2%), 9월에 Pseudo-nitzschia delicatissima(94.3%), 11월에는 Chroomnnas류(33.6%)로 변화하였다. 5월과 9월은 한 종이 전체 식물플랑크톤 개체수의 80% 이상을 차지하는 극우점양상을 보여주었고, 7월에는 C. curvisetus, Skeleton듬 costatum 및 Chaetoceros sp. 등이 유사한 점유율로 우점하고 있었다. 영산강 하구역의 식물플랑크톤 종다양성지수는 0.228$\sim$2.260의 범위로 소수의 우점종에 의해 전체 군집의 분포양상이 결정되는 전형적인 연안, 하구수역의 군집 특성을 보이고 있었다.

• Korean Journal of Ecology and Environment
• /
• v.52 no.4
• /
• pp.285-292
• /
• 2019

Our study was based on the long-term surveys with respect to the major reservoirs located in the Yeongsan and Seomjin river basins. A total of 45 survey sites have been surveyed four times a year from 2008 to 2017. We identified 166 zooplankton species, including 127 rotifers, 26 cladocerans, and 13 copepods. Mean population density and species number of small reservoirs were higher than those of mid and large reservoirs. Considering outliers exceeding the 90th percentile between species occupancy and mean abundance, 10 of 11 habitat generalists were rotifers, and Bosmina longirostris was the only cladoceran. Habitat specialist consisted of three species of rotifers and emerged from one to three survey sites. According to the modularity results, it was found that the survey sites covering the entire river basins were characterized into five groups, which was similar to the classification by maximum water surface areas(MWSA). The result of the eigenvector centrality showed that the size of MWSA had a greater impact on the similarity of zooplankton community structure between reservoirs than the difference in distance between reservoirs. In the case of survey points in near dam or estuary bank of Juam and Youngsan reservoirs, modularity class were separated from other internal survey points of those. Given that the zooplankton interactions may contribute to freshwater functions more than species diversity. These topological features provide new insight into studying zooplankton distribution patterns, their organization and impacts on freshwater-associated function.