Five-stage flood routing for gated reservoirs by grouping floods into five different categories according to their return periods

A five-stage operation policy for routing of flood hydrographs of return periods from 1.01 year up to the Probable Maximum Flood through reservoirs having gated spillways is suggested. The gate opening rules are determined based on the recent pool level only. Without having to predict the magnitude of the incoming flood hydrograph beforehand, the fixed rules of the five-stage operation policy will provide efficient routing for any flood of any magnitude.