Comparison of hydraulic and hydrologic routing on three, long reservoirs

Outflow hydrographs for three dams with long lakes in narrow valleys were computed by both hydrologic routing (level-pool routing) and hydraulic routing. They were compared with three inflow hydrographs of different peaks with three unregulated ogee spillways of different capacities. In all these cases, the difference between outflow hydrographs was greatest at the peak value, growing larger as the spillway capacity became smaller, relative to the magnitude of the inflow hydrograph. The peak outflow by hydraulic routing was smaller than that by hydrologic routing for all the routing combinations, the difference varying between 2 and 11%.