Fig. 2 e Schematic representation e (a) Contamination impact matrices. Each impact matrix represents the impact of a
contamination event on system nodes. The black block indicates that node xj is affected by the event at time ti and the
extent of the impact. The white blocks indicate that the contaminant did not reach these nodes and the event cannot be
detected. (b) Fixed and mobile sensors tracking matrices. Each tracking matrix represents the trajectory of a sensor released
in different time and location. The light gray blocks indicate the location of the sensor, where xj are meshes points along
network pipes and ti are steps in time. The dark gray block indicates the location of a fixed sensor, which remains stationary
at all times. The white blocks represent all nodes that were not visited by the mobile sensors.