Operation of Hydropower Reservoirs for Flood Attenuation Andrea Maffio*, Leonardo Mancusi* 8 th International Conference on Hydroinformatics Conception, Chile 12-16 Gennaio 2009 POSTER SESSION * CESI RICERCA Hydropower reservoirs under certain circumstances may be used to attenuate and delay floods in order to contribute to protect the downstream territory. To permit flood volume to be stored in the reservoir, water elevation has to be lowered in advance to partially emptying the reservoir. In order to attenuate and delay efficiently floods while limiting decrease of hydropower production and impounded water volume (useful for other uses e.g. irrigation, drinking, etc.) it would be necessary to change, during the flood event, water elevation by opening/closing dam outlets in accordance with flood hydrogram in order to contain reservoir emptying. This “dynamic” way of dealing with the flood (whereas a “static” way would lower water elevation notwithstanding flood hydrogram) would imply the prediction of flood events in terms of onset and time evolution. In the frame of the research financed by the Research Fund for the Italian Electric System, a hydrology- hydraulics-meteo integrated software tool has been developed to support operation of hydropower reservoirs for flood attenuation and delay. The software tool, capable of estimating flood hydrograms entering the reservoir and propagating downstream dam, implements mathematical modules relevant to most important processes and data involved e.g. meteo data, runoff estimate at watershed scale, reservoir operation maneuvers, flood propagation prediction downstream dams. The software is based on a graphic interface integrated with GIS funcionality and automatic update of meteo forecasts with data exchange between Web service clients. To evaluate tool capabilities and performance an Italian hydropower reservoir, used for flood attenuation, has been considered and actual flood events studied as pilot application.