More than 100 of the 330 opened bays of the Spillway have been closed, though water is still seaping through the closed bays at great speed. You can tell the River is still high because of the height of the ship compared to the Spillway in the foreground. A gradual drop is better than a speedy drop to prevent "caving in" of the river banks.
Ships have to maintain a certain speed to keep the current from taking control of them and turning them sideways or pushing them into the banks.