NUMERICAL ANALYSIS ON THE CHANGE OF PHYTOPLANKTON AND DISSOLVED OXYGEN AND THE EFFECT OF GATE OPERATION IN UPSTREAM AREA OF NAGARAGAWA ESTUARY BARRAGE

In the upstream area of Nagarariver estuary barrage, the high increasing of phytoplankton and decreasing of dissolved oxygen (DO) are occurred and these water quality changes are examined as the typical water quality problem on water area of Nagarariver estuary barrage. In this study, the analysis model developed for the examination of the water quality change. The validity of this analysis model, which is consist of the analysis of water flow, water temperature, chlorophyll, DO etc., is evaluated by comparing with observed data. And the method of the gate operation is discussed for the improvement of bad situation of water quality ( i.e. decreasing of DO). From this study, the keep of gate operation with under flow causes the decreasing of DO at near upstream and bottom region of the gate.