Study on Water Quality Dynamics in Up-and Down-steam region of Estuary Barrage Concerned with Its Operation

在对“长江口拦河口监测资料”进行统计分析的基础上，对长加拉河口拦河口上游区域的水质特征进行了评价研究。首先，利用FFT(一次傅立叶变换)对叶绿素a和溶解氧数据进行光谱估计。叶绿素a数据除具有季节性和日期性的波动成分外，还具有受洪涝影响的10天左右的波动成分。其次，利用数量化理论I研究了长加拉河下游河段水体中叶绿素a和溶解氧的控制因子及其特征，发现水温和热力层结的发育是影响叶绿素a和溶解氧绝对值的最主要因素，但这些因子随季节变化而变化。利用声学多普勒水流剖面仪和水质观测面…的观测资料对长加拉河河口拦河口下游的水流特征进行了估算更重要的是，来潮时长江口拦河口下游地区的水流受河口密度状况的影响。在河口低密度水存在的情况下，由于底部高密度水的存在，水流变成两层流。在河口存在高密度水的情况下，水流进入河流的深部。在退潮的情况下，下游水流通过高密度水。这种现象与河口拦河口下游地区DO的减少有关。在大潮期间，由于从拦河口到与伊比河交界处的水位比伊比河上升得更快，潮水流入伊比河。在1995-1999年夏季，对长加拉河河口拦河口上游的水流和水质进行了数值模拟。模拟结果表明，疏浚改变河床形态影响水流特性，流量、风速和风向、闸门运行通过藻类的产生和积累影响藻类种群的时空分布。在对拦河口下游区域水流和盐分行为的数值分析中，模拟结果定性地反映了观测得到的真实行为。较少

The study to estimate water quality characteristics in up-stream area of Nagara River Estuary Barrage has been done based on statistical analysis of "Nagaragawa Estuary Barrage Monitoring Data". First, spectra of chlorophyll-a and DO data are evaluated by means of FFT(First Fourier Transform). Chlorophyll-a data have fluctuation component of about 10 day period affected by flood inflow in addition to fluctuation components of seasonal period and day period. Secondly, governing factors of chlorophyll-a and DO and their characteristics are investigated by means of Quantification Theory I. It is found that water temperature and growth of thermal stratification are the most important factors for the absolute value of chlorophyll-a and DO, though the governing factors seasonally change.Flow characteristics in downstream area of the Nagara River Etuary Barrage are estimated by means of observed data obtained from ADCP(Acoustic Doppler Current Profilers) and observation plane for water qualit … More y. The flow in downstream area of the Nagara River Estuary Barrage in inflow of the tide is affected by the situation of density in mouth of river. In the case of existence of Low density water in mouth of river, the flow becomes two layer flow because of existence of high density water in bottom. In the case of existence of high density water in mouth of river, the flow get into deep area of river. In the case of the ebb tide, down stream flow pass upon high density water. This phenomena is concerned with decreasing of DO in downstream area of the estuary barrage. In the spring tide, inflow of the tide pass to the Ibi River because the water level in the area from the barrage to joint point with the Ibi River more rapid increase than the Ibi River.Numerical Simulation of the flow and water quality in the upstream area of Nagara River Estuary Barrage has been done under real conditions in the summer seasons of 1995-1999. The results obtained from the simulations indicate that change of the river bed shape by dredge influence the flow characteristics, and that flow discharge, wind velocity and direction, gate operation at the barrage concern the temporal and spatial distribution of algae populations through the production and accumulation of them. In the numerical analysis of the flow and salt behavior in the down stream area of the barrage, the simulation results qualitatively represent their real behavior obtained from the observation. Less