Risk management can be defined as socio-economic decision-making process (Rak 2009). It is obvious that it is impossible to eliminate risk, but system operator can take any action to minimize it. Decision-making is the responsibility of the operator of the WDS. Therefore, to avoid the negative consequences of making wrong decisions regarding WDS operation, the operator must learn how to assess risk, inform others of its size, and know what action must be taken in critical situations (Zio 2006).