In recent years, researchers worldwide have turned their attention towards the problem of water discoloration in distribution systems. This problem has increasingly affected many cities including Bogotá (Colombia), forcing its water utility in 2008 to undertake actions to understand the nature of the turbid water for future mitigation actions. Due to the fact that the detachments occurred inside the trunk network, none of the available techniques in the literature could be applied directly. This paper presents an adapted methodology based on hydraulic simulation and field data to model and understand discoloration events that occurred in large trunk networks. It was successfully tested on the Bogota's trunk water distribution system, as the actual places of film detachment and its nature could be established. These results prove essential to help formulate strategies for the mitigation of the impact of future events.