Variable sets and the theorem and method of optimal decision making for water resource system

The theory of variable fuzzy sets is developed to variable fuzzy and clear sets referred to as variable sets. Study and establish the unity of opposite theorem that the clarity and fuzziness both change dynamic and get the research applied into the practice of optimal decision making for water resource system. Proposed the variable sets’ unity of opposite theory and raised the principle and method of water resource system optimization decision making based on the variable sets. Given two examples of application, compared and analyzed with the Extenics and Fuzzy set pair analysis optimal method in detail. The result shows that the variable set is not only useful to optimizing assessment for the water resource system, but also for the other system, such as the water conservancy and hydropower, civil engineering system and many other fields’ optimal decision making, having the broad application potential.