Ensemble hydrologic prediction has been widely adopted by water management and forecast agencies in US and abroad.  This talk introduces the basics of ensemble hydrologic forecast, and discusses its potential in improving water management and hazard preparedness. Basic components of the current hydrologic ensemble forecast system at National Weather Service, in particular the ensemble preprocessor, will be described.  Also discussed are recent improvements to the preprocessor, including the introduction of alternative shuffling mechanism and statistical processing paradigm.  The merits of ensemble prediction for reservoir management and flood prediction will be highlighted.