• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.263-269
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• 1995

To determine the autochthonous COD caused by the production of phytoplankton, three different methods were used simultaneously utilizing several environmental factors and applied to the Nakdong Estuary. From the estimation of the tropic state index, tropic level in the Nakdong Estuary was found to be in excess of eutrophication level at all area studied. The percentage of autochthonous COD in total COD was largest in summer and in station No. 6 $(43.5\%)$. Using of the relationship between COD and salinity was not appropriate tov the evaluation of the autochthonous COD due to discrepancy with other tesulfs evaluated. However, the evaluations of autochthonous COD obtained from the $\DeltaCOO$ and the relationship between COD and chl.a were found to be proper methods, resulting in a relative error less than $20\%$ for all of the area investigated.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.2
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• pp.113-123
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• 2005

Samples were collected to investigate the effect of salinity change on biological interaction between primary producers and herbivores in water column of the Youngsan estuary (Mokpo Harbor) at 8 stations from October 2003 to September 2004. The highest river freshwater inputs were introduced into the estuary from the Youngsan dike during summer (June and July 2004). Ranges of salinity were between 6 and 28.9 psu when the gates of dike were open whereas the ranges were between 24.4 and 30.3 psu when the gates were closed. Algal bloom occurred in February and July when the gates were not open at the upper region of the Youngsan estuary and the bloom was dominated $(70\%)$ by large cells of phytoplankton $(micro-sized;>20{\mu}m).\;Nano-sized (2-20{\mu}m)$ and pico-sized phytoplankton $(<2{\mu}m)$ were dominant in October, November 2003, June, August and September 2004 when the gates were open suggesting that size structure was affected by river discharge from the dike. Micro-and meso-zooplankton (herbivores) displayed the similar pattern to that of phytoplankton. The biomass of zooplankton was higher when the gates were closed than when the gates open and also the biomass was higher at the upper region of the harbor system. This results suggest that freshwater inputs affect size structure and biomass of phytoplankton by changing salinity, nutrient inputs, turbidity or light level In water column resulting in the change of the interaction between primary producters and herbivores in the Youngsan estuary.

• Korean Journal of Ecology and Environment
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• v.46 no.2
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• pp.205-214
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• 2013

In Yeongsan River estuary, located in the southern West Coast, a dike was constructed in December 1981. After the construction of a dike, discharge mechanism of fresh water has been changed, the water quality and chlorophyll-a are expected to be influenced by fresh water discharge. We investigated temporal and spatial variations and long-term trend of phytoplankton biomass (chlorophyll-a) and environmental factors. The concentrations of nutrient and chlorophyll-a were generally high in summer and the concentrations were increased toward downstream. Surface/bottom salinity difference was negatively correlated with salinity in surface water but positively with nutrient and chlorophyll-a. TN, TP and DIN concentrations were generally increased over 10 years. This study can provide information for better management of water quality for Youngsan River estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.4
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• pp.218-224
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• 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 Korean Society of Coastal and Ocean Engineers
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• v.7 no.4
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• pp.321-328
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• 1995

The FIT(fully implicit tidal) model which adopts PCGCS (preconditioned conjugate gradient squared) method is developed and is applied to near Mokpo Harbor. Comparing computational results with observed velocities and elevations for the M$_2$ tidal constituent, agreeable correspondence is detected. The validity of the model is also proven by applying it to such areas which have narrow width (therefore showing rapid velocity), irregular topography and complex geometry. Tidal amplification phenomenon according to the constructions of seadike and sea-walls is considered by analyzing the 'filter effect' of Mokpo-ku using the model.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1007-1011
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• 2004

영산강하구언과 영암 및 금호방조제 건설에 의해 목포해역에서는 조석확폭현상이 발생하여 만조위가 상승함에 따라 저지대에 침수피해를 야기시킨 바 있다. 이는 목포구의 'tidal choking effect' 기능이 상실됨에 기인한다는 결론을 선행인구(강주환, 1996)에서 얻은 바 있다. 본 인구에서는 선행연구에 비해 전체 영역이 확대되었으며 격자크기가 작아졌을 뿐 아니라 관심영역에는 세부역을 도입하여 더욱 세밀한 격자체계를 구성하였다. 이에 따라 조간대 처리가 한층 정밀해졌으며, 천해조 경계조건 부여와 함계 낙조우세를 실제에 가깝게 재현시킬 수 있게 되었다. 또한 방조제 건설후 낙조우세가 심화되는 자정을 모의할 수 있게 됨에 따라 소류사 이동양상의 변화된 패턴 역시 파악할 수 있었으며, 만조위 상승에 따른 침식유발 효과와 더불어 인근 해역의 침식 원인을 부분적으로 규명할 수 있었다.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1018-1022
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• 2004

지구온난화에 의해 전세계적으로 평균해수면이 상승하고 있는데, 이는 지반의 융기 또는 침강 등을 비롯한 여러가지 지역적 차이 때문에 지역적으로 적지 않은 차이를 보이고 있다. 분석결과에 따르면 서남해안은 $1\~3mm/yr$ 정도의 비슷한 값을 보이고 있으며 제주도의 경우 $3\~5mm/yr$로 서남해안 지역에 비하여 약간 큰 값을 보이는 등 전지구적 상승량인 $1\~2mm/yr$ 보다는 다소 크게 나타나고 있다. 이와 함께 방조제와 같은 해안구조물 건설에 의해서도 평균해수면 뿐 아니라 고조위 및 저조위의 변화가 유발된다. 서남해안에서는 군산항과 목포항에서 특히 방조제 건설후에 각각 조위상승과 조석확폭현상이 발생하여 만조위 상승이 유발된 것으로 나타나고 있는데, 여기에 기인하여 목포 인근해역에서는 침식현상이 초래되고 있을 뿐 아니라 연중 해수면 변화가 심해짐에 따라 고극조위가 더욱 커져 저지대 범람이 특히 우려되고 있는 실정이다.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.160-180
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• 2005

Long-term data (Ministry of Environment Water Quality Monitoring data) of phytoplankton biomass (chlorophyll a) and water quality were analyzed to investigate trends in biomass of the primary producers and water quality for the estuarine systems in Korea: Sumjin River, Han River, Asan Lake- Bay, Youngsan River, Keum River and Nakdong River. The literatures were also reviewed to examine the characteristics of phytoplankton biomass and water quality in the estuarine systems. The Sumjin River estuary, the single estuary without a dike in Korea showed the characteristics similar to other typical estuarine systems. Phytoplankton biomass was high during the fall at transitional regions (5 ${\sim}$ 15 psu) after riverine freshwater inputs were increased in summer. Concentrations of the nitrate and silicate were increased with the high river discharge rates. Phytoplankton biomass and nutrient concentrations were high during spring at the lower regions in the Han River whereas phytoplankton biomass and nutrient concentrations were high during spring at the upper regions in the Youngsan River. Phytoplankton biomass was the highest in the Asan Lake and nutrient concentrations were high at the upper region of the lake. In Nakdong River, phytoplankton biomass was high during winter and the biomass was slightly higher at upper region than at lower region. Long-term trends showed that total nitrogen and total phosphorus were mostly increased in the river systems. Implications of these results relevant to the water quality management for the river systems were also discussed.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.433-437
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• 2007

최근 환경부에서는 낙동강 유역의 오염총량관리제도의 시행에 따라 이제까지의 배출구 수질기준으로부터 총량수질기준을 통한 수질관리를 실시하고 있다. 오염총량관리를 실행하기 위해서는 주요지천 및 폐수처리장에서의 수질개선 및 비점오염원 관리가 선행되어야 하는데 이를 효율적으로 제어하기 위해서 낙동강 유역에 적합한 최적 수질해석 모델의 개발이 요구되는 상황이다. 수질모델의 가장 큰 목적은 유역으로부터 발생한 오염물이 하천으로 유입되었을 때 하천 수질 및 생태계의 수학적 표현을 통해 장래의 수질을 예측하고, 예측된 결과에 따라 합리적인 수질관리대책을 수립하는 것이다. 낙동강은 대표적인 수지상 하천망의 형태로서 댐 방류량 및 지류유입량은 본류 수계에 직접적인 영향을 미치며, 수질해석의 기본이 되는 수리계산에 매우 중요한 변수가 된다. 또한 대구, 구미, 왜관, 김천 등에서의 오염부하가 금호강, 남강 등의 주요 지류를 통하여 본류부로 유입되고 있으며, 하류부 칠서, 원동, 매리, 물금 등에서는 대량의 하천수를 취수하여 부산, 울산, 마산, 창원 지역 등의 생활 및 공업용수의 원수로 사용하고 있다. 다시 말해서 댐 방류량, 낙동강 하구언의 수위조절, 지류 유입량, 비점원 유입량 등 계산영역 경계에서의 비정상상태의 수리조건과 수질관리 계획에 의해 일률적으로 오염이 부하되는 정상상태의 수질조건이 공존하고 있는 실정이다. 본 연구에서는 낙동강 유역에 적합한 동적 수질모델을 개발하였다. 본 연구에서 개발된 수치모형은 갈수저수조건 및 불규칙한 하도단면을 반영하고, 동적 상태의 댐 방류량, 낙동강 하구언의 수위조절 영향, 지류 유입량 등 다양한 하천조건에서 발생하는 동적 흐름을 안정적으로 해석하여 낙동강 수질해석의 신뢰도를 향상시킴으로서 낙동강에 유입된 오염물질이 수계에 미치는 영향을 정확히 분석하고자 하였다. 동적수질해석에 의한 모의결과는 유량의 경우 상류부분은 모의치와 실측치가 잘 일치하지만, 중류 이후 지류의 유입이 많아지면서 지류의 변화를 정확히 입력하지 못해 모의치와 실측치의 차이가 발생한다. BOD의 경우는 수질이 양호한 상류지역은 모의치와 실측치가 잘 일치하지만, 오염원의 유입이 많은 중류지역부터는 실측치와 차이를 나타내다가 하류지역에서 다시 비교적 일치함을 알 수 있다. TN의 경우는 전반적으로 실측치보다 높게 모의되었고, TP는 전반적으로 실측치와 비교하여 잘 모의되었다. 본 연구에서 구축한 동적 수리해석모형 및 동적 수질해석모형은 낙동강 유역에 대해 유량 및 수질 등의 실제 하천의 경향에 비교적 잘 반영하므로 오염물총량규제에 따른 합리적인 하천 수질관리대책을 수립하는데 크게 기여할 수 있을 것으로 기대된다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.4
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• pp.259-268
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• 2005

There has been a growing interest in the elimination of anoxic layer in the Youngsan River Estuarybecause the anoxic water mass caused mainly by the inflow of fresh water from the sea wall might cause the mass reduction of benthos during summer. An ocean outfall system to discharge treated wastewater into sea water may be used as one of the effective and economical ways to eliminate the anoxic layer. The suitable ocean outfall design is generally proposed for the prediction of the buoyant jet behavior in the near field. The parameters including CTD and current data are taken into account f3r more reliable buoyant jet behavior calculation. One of the numerical models, CORMIX 1, approved by EPA is used herein for the prediction of the trajectorial variation of the cross-sectional salinity and DO concentration distribution on the calculated buoyant jet boundary according to the tidal periods. On the basis of the results, it is suggested that the single port outfall is a useful system to eliminate the anoxic layer. Proper strategies are also proposed for achieving desirable ambient conditions.