For the purpose of safe operation of the water distribution system of Shanghai Shibei Water Company, a mathematical model of the pipe network is being established, and computer software is being developed. Multi-functions of the model includes time-depending changes of the water flow and water quality in the distribution network, covering the area of 400 km2 and serving the population of 3.5 million. It will provide new techniques for safety management of water supply and for improving customer services.