Safety of Spillway Radial Gates

Spillway radial gates, whether located on top, or inside the body of a dam, or on a structure separate from the dam, are in fact mobile dams. They are one of the most critical appurtenances, because safety and operational reliability of the spillway gates is crucial not only for attenuating flood peaks, regulating outflows and abating downstream flooding, but also for storing water for usage during the dry periods, and for generation of power.
For many hydropower projects, the cream which produces dependable, as well as, peaking power and thus the most secure and highest revenues, is stored behind the spillway gates. For projects where the normal annual reservoir drawdown is less than the height of the spillways gates, the entire power production and thus the financial and economic well-being of the project, is dependent on the safety and reliability of the spillway gates. A pertinent example is the bi national Itaipu Project, jointly owned by Brazil and Paraguay. Its powerplant with an installed capacity of 12,600 MW generated over 69,000 GWHrs of energy during 1994. Yet during the last 12 years of its operation the reservoir was never lowered below the spillway crest; in fact, the maximum annual drawdown was less than 1.0 m.