Journal of the Korean Society of Marine Environment & Safety (해양환경안전학회지)

The Korean Society of Marine Environment and safety (해양환경안전학회)
권호 표지
DOI QR코드

DOI QR Code

Effect of Freshwater Discharge on the Nakdong River Estuary: Mooring Observations of Water Temperature and Salinity

낙동강 하구의 담수 방류와 표층 수온 및 염분 반응 : 계류형 센서 연속관측 결과

  • Kim, Sangil (Ocean Climate & Ecology Research Division, National Institute of Fisheries Science) ;
  • Youn, Seok-Hyun (Ocean Climate & Ecology Research Division, National Institute of Fisheries Science)
  • 김상일 (국립수산과학원 기후변화연구과) ;
  • 윤석현 (국립수산과학원 기후변화연구과)
  • Received : 2019.01.15
  • Accepted : 2019.02.25
  • Published : 2019.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

Mooring observations of water temperature and salinity were conducted to investigate the effects of freshwater discharge patterns on the mouth of Nakdong River from April 2017 to March 2018. More than $500-1000m^3\;s^{-1}\;d^{-1}$ of freshwater was frequently discharged into the estuary throughout the rainy season, but less than $200m^3\;s^{-1}\;d^{-1}$ was discharged through the normal season. Sluice gates of the estuarine barrage operated depending on the tide level during spring tide, but they were constantly open during neap tide. Water temperature and salinity fluctuated regularly with intermittent discharges of freshwater, whereas they were stable while freshwater discharge was continuous. Mean salinity was 29 during the study period. Salinity exceeded the mean value in the normal season and rapidly recovered after a temporary reduction. In contrast, water with salinity below the mean value prevailed in the estuary for three months over the rainy season. These results indicate that water temperature and salinity were affected by the amount of freshwater discharge, as well as the frequency of discharge on a large scale and the time over which the freshwater discharge continued.

낙동강 하구에서 연속관측 자료를 바탕으로 담수의 방류와 수온 및 염분의 시간에 따른 반응을 조사하였다. 낙동강 하구 서쪽 해역에 계류형 센서를 설치하고 2017년 4월 1일부터 2018년 3월 31일까지 10분 간격으로 수온과 염분을 측정하였다. 담수의 방류량은 평상시에 $200m^3\;s^{-1}\;d^{-1}$ 이하로 유지되었으나, 풍수기에는 $500{\sim}1000m^3\;s^{-1}\;d^{-1}$ 이상의 많은 양의 담수가 빈번하게 방류되었다. 담수의 방류는 대조기에는 간조를 전후하여 발생하였고, 소조기 동안에는 계속적으로 일어났다. 평상시에 수온과 염분은 소조기 동안 큰 변동 없이 안정되는 경향을 보이는 반면에, 대조기에는 방류주기에 따라 규칙적인 변동을 나타내었다. 연구기간 동안 염분은 평균 29이었으며, 평상시에 염분 농도는 평균 이상으로 유지되었고 일시적인 감소 이후에도 빠르게 회복되었다. 풍수기에는 약 3개월 동안 평균 이하의 저염환경이 지속되었다. 이러한 결과는 담수의 방류량뿐만 아니라 방류의 지속시간과 대량 방류의 빈도가 낙동강 하구의 표층 수온과 염분의 변동성에 영향을 미치는 중요한 요인이 된다는 것을 의미한다.

Keywords

References

  1. Chen, X., M. S. Flannery and D. L. Moore(2000), Response times of salinity in relation to changes in freshwater inflows in the lower Hillsborough River, Florida, Estuaries, Vol. 23, No. 5, pp. 735-742. https://doi.org/10.2307/1352899
  2. Chevailer, C., M. Pagano, D. Corbin and R. Arfi(2014), The salinity responses of tropical estuaries to change in freshwater discharge, tidal mixing and geomorphology: case study of the man-affected Senegal River Estuary (West Africa), Marine and Freshwater Research, Vol. 65, Nov. 11, pp. 987-1002. https://doi.org/10.1071/MF13169
  3. Han, K. M., K. C. Kim and J. J. Kim(1993), A study on the flow patterns on the Myunggi-Noksan region due to Reclamation, Journal of ocean engineering and technology, Vol. 7, No. 1, pp. 81-91.
  4. Jannasch, H. W., L. J. Coletti, K. S. Johnson, S. E. Fitzwater, J. A. Needoba and J. N. Plant(2008), The land/ocean biogeochemical observatory: A robust networked mooring system for continuously monitoring complex biogeochemical cycles in estuaries, Limnology and oceanography: Methods, Vol. 6, pp. 263-276. https://doi.org/10.4319/lom.2008.6.263
  5. Jang, S. T. and K. C. Kim(2006), Change of oceanographic environment in the Nakdong Estuary, The Sea, Vol. 11, No. 1, pp. 11-20.
  6. Johnson, K. S., J. A. Needoba, S. C. Riser and W. J. Showers(2007), Chemical sensor networks for the aquatic environment, Chemical Reviews, Vol. 107, pp. 623-640. https://doi.org/10.1021/cr050354e
  7. Kim, K. C., J. J. Kim, Y. E. Kim, K. M. Han, K. K. Choi and S. T. Jang(1996), Outflow characteristics of Nakdong River Plume, Journal of the Korean Society of Marine Environment & Safety, Vol. 8, No. 4, pp. 305-313.
  8. Kim, K. C., H. S. Yang, C. K. Kim, C. H. Moon and S. T. Jang(1999), Variations of physical oceanographic environment caused by opening and closing the floodgate in Nakdong Estuary, Journal of the Korean Society of Marine Environmental Engineering, Vol. 2, No. 2, pp. 45-59.
  9. K-water(2015), Manual for operating the Nakdong Estuary Barrage.
  10. Lane, R. R., J. W. Day Jr, B. D. Marx, E. Reyes, E. Hyfield and J. N. Day(2007), The effects of riverine discharge on temperature, salinity, suspended sediment and chlorophyll a in a Mississippi delta estuary measured using a flow-through system, Estuarine, Coastal and Shelf Science, Vol. 74, pp. 145-154. https://doi.org/10.1016/j.ecss.2007.04.008
  11. Lerczak, J. A., W. R. Geyer and R. J. Chant(2006), Mechanisms driving the time-dependent salt flux in a partially stratified estuary, Journal of Physical Oceanography, Vol. 36, No. 12, pp. 2296-2311. https://doi.org/10.1175/JPO2959.1
  12. Lee, S. J., K. S. Ryoo, M. H. Hwang and S. U. Lee(2008), Analysis of the water quality by various gate operation effects at Nakdong Estuary Barrier, Journal of Korean Society on Water Quality, Vol. 24, No. 6, pp. 651-658.
  13. Magnuson, J. J.(1990), Long-term ecological research and the invisible present, BioScience, Vol. 40, pp. 495-501. https://doi.org/10.2307/1311317
  14. Monsen, N. E., J. E. Cloern, L. V. Lucas and S. G. Monismith(2002), A comment on the use of flushing time, residence time, and age as transport time scales, Limnology and Oceanography, Vol. 47, No. 5, pp. 1545-1553. https://doi.org/10.4319/lo.2002.47.5.1545
  15. Moon, C. H. and H. J. Choi(1991), Studies on the environmental characteristics and phytoplankton community in the Nakdong River estuary, The Journal of the Oceanological Society of Korea, Vol. 26, No. 2, pp. 144-154.
  16. Park, C. K., K. D. Cho, S. H. Huh, S. K. Kim and C. H. Kim(1986), Ecological Survey of the Nakdong River Estuary, Bulletin of the Korean Society of Fisheries Technology, Vol. 22, No. 4, pp. 1-20.
  17. Park, S., H. S. Yoon, I. C. Lee and H. T. Kim(2008), Correlation between Meteorological Factors and Water Discharge from the Kakdong River Barrage, Korea, Journal of the Korean Society of Marine Environment & Safety, Vol. 14, No. 2, pp. 111-117.
  18. Vijith, V., D. Sundar and S. R. Shetye(2009), Time-dependence of salinity in monsoonal estuaries, Estuarine, Coastal and Shelf Science, Vol. 85, No. 4, pp. 601-608. https://doi.org/10.1016/j.ecss.2009.10.003
  19. Yoo, M. H., S. H. Youn, K. W. Park, A. R. Kim, S. C. Yoon and Y. S. Suh(2016), The Characteristics of Spatio-Temporal Distribution on Phytoplankton in the Nakdong River estuary, during 2013-2015, Journal of the Korean Society of Marine Environment & Safety, Vol. 22, No. 6, pp. 739-749.
  20. Yoon, S. C., S. H. Youn and Y. S. Suh(2017), The characteristics of spatio-temporal distribution on environmental factors after construction of artificial structure in the Nakdong River estuary, Journal of the Korean Society of Marine Environment and Energy, Vol. 20, No. 1, pp. 1-11. https://doi.org/10.7846/JKOSMEE.2017.20.1.1
  21. Yu, H. S. and J. Lee(1993), A hydrodynamic solution for the lateral spreading of a river plume, The Journal of the Korean Society of Coastal and Ocean Engineers, Vol. 5, No. 4, pp. 302-306.
  22. Yu, H. S., J. Lee, H. J. Kang, S. R. Kang, K. S. Choi and J. S. Kim(1993), Lateral spreading of a river plume and transport of suspended sediments in the Nakdong estuary, The Journal of the Korean Society of Coastal and Ocean Engineers, Vol. 5, No. 4, pp. 296-301.