One of the processes that was in research during last years, with the aim to be optimized on both costs and demand fulfillment, has been the operation of complex water supply systems, i.e. those interconnected systems having numerous elements like sources, clean and raw water pumping stations and reservoirs, power generation plants, water treatment plants, etc. Within this work an optimum dispatch model proposal was designed for the Empresas Publicas de Medellin water supply system, taking into account all physical, operational and legal restrictions. The model was developed by Mixed Integer Linear Programming. The model made use of all operational posibilities of the interconnected system and also fulfilled strictly all restrictions, so that an operational proposal was obtained in which costs are lesser than real historic operational costs and there is always water demand compliance. Nowadays, said model became an additional tool, used as a guide for operation of the interconnected Empresas Publicas de Medellin water supply system.