As a limited resource, especially under market conditions, water should be managed at the highest level of efficiency. This approach, however, leads to a conflict with the sustainability principle. At the basic level it could be defined as a question: ‘Is the market eager to pay the sustainability cost?’ If it is, then the cost of sustainability shall be determined and explicated in the price of water unit delivered to the customer. If not, sustainability is then jeopardized. The solution to this conflict may be a test from a responsible aspect for the current generation towards water resources. This paper aims to research the management of water resources methods from the aspect of sustainability under the conditions of uncompleted and uncertain information. In this paper, the model for water resources availability forecasting is analysed from the aspect of different influences.