In crisis management, risk assessment is fundamental for decision-making to ensure the safety of water supply systems. The presented risk assessment method originates from safety engineering. The novelty of the method lies in the distinction between material and human losses. By definition, risk assessment involves multiplying the probability or frequency of a hazard by the projected losses. This study addresses the issue of estimating the probability of emergency events within a specific time frame. To estimate material losses, a percentage of the revenue of a local government unit (city, municipality) is proposed. Three types of human losses are distinguished: medical assistance, required hospitalization, and fatality. The risk assessment is based on a four-parameter risk matrix using the following formula: where: P – probability of hazard occurrence, C – material losses, F – human losses, O – protection.