Discharge ratings for control gates at Mississippi River Lock and Dam 18, Gladstone, Illinois

The water level of the navigation pools on the Mississippi River are maintained by the operation of tainter and roller gates at the locks and dams. Discharge ratings for the gates on Lock and Dam 18, at Gladstone, Illinois, were developed from current meter discharge measurements made in the forebays of the gate structures. Methodology is given to accurately compute the gate openings of the tainter gate. Discharge coefficients, in equations that express discharge as a function of tailwater head , forebay head, and height of gate opening, were determined for conditions of submerged-orifice and free-weir flow. A comparison of the rating discharges with the hydraulic model rating discharges is given for submerged orifice flow for the tainter and roller gates.