Flood control for reservoirs require operations in a dynamic and cooperative manner in order to respond to the changing flood control conditions. There is an increasing emphasis on the collaboration of multiple partners with different backgrounds by sharing data, models and analysis tools in a user-friendly environment, thereby making analysis and evaluation more convenient. One of the key objectives of this paper is to exploit the Web as an infrastructure for running distributed applications that will address reservoir system operation. The web-based flood control system for reservoirs presented in this paper supports the entire decision-making process, including preprocessing the real-data observed data, setting initial conditions, selecting reservoirs constraints, interactively generating alternatives, evaluating alternatives and querying modeling analysis results and recommending alternatives. The system has been implemented in a real flood control management system in China.