Drinking water distribution networks are exposed to malicious or accidental contamination. Several levels of responses are conceivable. One of them consists of installing a sensor network to monitor the system in real time. Once a contamination has been detected, it is also important to take appropriate counter-measures. The SMaRT-OnlineWDN project relies on modelling to predict both hydraulics and water quality. An online model makes it possible to identify the contaminant source and perform a simulation of the contaminated area. The sensor system is intended for detection by an early warning system and for online calibration of the transport model. The main objective of this deliverable report is to specify which performance criteria should be considered to place water quality and water quantity sensors for both early detection and model calibration. Firstly, a review of previously published research on water security and model calibration is presented. Then, the experiences of partners in the two previous German National projects, STATuS and IWaNet, and in the FP7 European project, SecurEau, are reported. Next, formulations and objectives for early warning detection are proposed. Following, problem formulations that aim to minimize the estimator variance for calibration are specified. Finally, a summary of the conclusions is given.