The technology of predicting turbidity distribution with sufficient accuracy is necessary in the construction sites at sea since circumference environment may be affected if the turbidity flows out from the construction area. This research developed a system to predict the three-dimensional flow of the next day on the daily basis for the land reclamation site of the Osaka Bay Phoenix Project. Since the construction site is located near the mouth of the Yodo River, tidal flow, wind-induced flow and density flow are calculated at the same time. This system gains the input data especially the wind and the flow rate of river discharges every day. The system was verified by the field observation at the site. Through these preparations, this system started to distribute the prediction results in November 2002 and they are referred for the daily construction management.