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HOW NAVIGATIONAL LOCKS OPERATE These diagrams show how a ship is lowered in a lock—a ship is raised by reversing the operation. No pumps are required; the water is merely allowed to seek its own level. With both UPPER GATES and LOWER GATES closed, and with the EMPTYING VALVE closed and the FILL- ING VALVE open, the LOCK CHAMBER has been filled to the UPPER LEVEL. then been opened allowing the ship to enter the LOCK CHAMBER. Now the ship is in the LOCK CHAMBER. The UPPER GATES and the FILING VALVE have bert and the EMPTYING VALVE has been opened to allow water to flow from the Lock HAMBER to the LOWER LEVEL. The water level in the LOCK nother downbound ship. UPPER GATES OPEN Lowen cates cuoseo.. UPPER GATES CLOSED LOWER GATES cLoseo UPPER GATES CLOSED. LOWER GATES OPEN Courtesy U.S. Corp of Engineers s are used after the close of navigation in order to remove the water fiom the locks. Considerable maintenance work is frozen over and steamboat whistles are no longer heard on the area waters are busy waterway. done during winter, when