Saline Water Movement In The Estuary Of The Nakdong River

낙동강 하구의 염수운동

Saline water movements in relation to tidal condition and river discharge in the estuary of the Nakdong River are discussed on the basis of the observation data. The difference of salinity between the surface and the bottom layer was 1∼3 at spring tide forming a vertically homogeneous estuary, while at neap tide, it ranges up to 7∼15 indicating a sharp salt wedge. The maximum salinity appeared approximately at an hour after the high water, that is, three hours after the landward velocity maximum, while the salinity maximum at around an hour after the low water, that is, three hours after the seaward velocity maximum. The density current speed at a section located 10km landward from the river mouth was observed approximately to be 45cm sec$\^$-1/ at 8m layer.The relations between the salinity at Gupo and the river discharge at Jindong are estimated by means of the least square method. The maximum length of the salt wedge is calculated approximately to be 22km at neap tide and 16km at spring tide, which is in accordance with the observed data. The salinity influence area is deduced to be 45km at spring tide and 35km at neap tide. The diffusion coefficient of salinity was estimated approximately to be 1.5 10$\^$8/$\textrm{cm}^2$ sec$\^$-1/ at Samrak and 8 10$\^$5/$\textrm{cm}^2$ sec$\^$-1/ at Gupo at neap tide, while it was 1.4 10$\^$7/$\textrm{cm}^2$ sec$\^$-1/ at Dongwon at spring tide.

우리나라 남동부의 광범한 유역을 따라 흐르는 낙동강은 국내에서 가장 긴 하천의 하나로서 영남지역을 굽이쳐 흐르다가 부산 앞바다를 통하여 대한해협에 유입한다. 이 강의 하구는 유역주민의 생활 및 산업용수원으로서 중요할 뿐만 아니라 최근에는 산업입지 및 자연환경 보전문제로서 논의의 대상이 되고 있다. 낙동강은 하구로부터 약 40km상류까지 상향류를 보이며, 약 60km상류까지 조석의 영향을 받는 감조하천으로서 (유 장 1979), 하구역에는 해수, 하천의 담수 및 양자의 혼합수가 조석의 간만등 여러 가지 요인에 따라 유출되기도 하고 유입되기도 한다.