Robust optimisation for inexact water quality management under uncertainty

An inexact fuzzy water management model is proposed and applied to a case study of water quality management within an agricultural system. The model is based on an interval-parameter fuzzy robust programming approach such that it can directly communicate uncertainties into the optimisation process and into the resulting solution by representing model parameters as interval numbers and/or fuzzy membership functions, and effectively handle highly uncertain information for the lower and upper bounds of interval parameters by introducing the concept of fuzzy boundary interval. Consequently, robustness of the optimisation process and the solution can be enhanced. Results of the case study indicate that useful solutions can be obtained to plan agricultural activities in the water quality management system. These solutions reflect a compromise between the optimality and stability of the study system: willingness to accept low agricultural income will guarantee system stability; however, a desire to acquire high agricultural income will run the risk of potential instability of the system. The results also suggest that the proposed hybrid methodology is applicable to practical problems that are associated with highly complex and uncertain information.