Due to the fact that water systems belong to critical infrastructure, diverse methods of its management assessment during crisis situations are applied. In these methods both technical aspects and human factors, that have an impact on safety of water supply to the recipient, are considered. Also assessment tools for water supply were applied for failure assessment in the water supply system (WSS) management. The safety functioning of WSS is associated with analysis of relations between threats, reducing the frequency of their appearing, and, if threats appear, with the identification of their causes and reducing their negative consequences. Undesirable events are the result of phenomena independent from the human will, as well as those related to human activity, that in a significant way influence the WSS functioning. Crisis situations that are affected by such undesirable events having nonrandom (rare events do not have the statistical stability), but also not-determined character, demand specific and interdisciplinary research methods.