Reservoir Operation by Fuzzy Reasoning

Abstract: The operation of lakes and reservoirs is currently under scrutiny in Finland due to the aging of the old operation permits, climate change, and changing environmental values. Simulation is a viable tool for studying reservoir operation but difficult to use when the operation does not have clear explicit rules. Fuzzy logic has been shown to be useful in modeling simple decision making which requires intelligence. Two fuzzy logic based methods, namely case-based and rule-based reasoning were examined and applied for modeling the operation of five lakes of a river basin. Different mathematical structures and interpretations were tested including the use of fuzzy similarity based approaches. The best results were obtained using a rule based ap-proach with a simple mathematical structure and interpretation of the fuzzy and as a product. The rule base in the model was allowed to be inconsistent and each rule had an associated weight or strength. The case-based approach performed rather well in comparison with the rule-based approach and in some cases better in some respect. Both models can mimic the human operator reasonably well in easy circumstances but have problems especially in the downstream lakes with large discharge to storage ratios. The fuzzy logic based models, case-based reasoning or rule-based reasoning require further work to be applicable in studying practical problems like the adjusting the operation to changes in environmental values and climate.