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Fuzzy Multiobjective Decision Making Approach for Groundwater Resources Management

A conventional simulation-optimization model with constraint on drawdown at an area of interest is used to optimize additional groundwater withdrawal at multiple demand locations in a coastal aquifer. After obtaining the optimal solution, a decision-making analysis is conducted using fuzzy logic concepts. The goal is to evaluate multiple objectives and select the best management strategy. This methodology is applied to a hypothetical case consisting of six groundwater demand locations in Savannah, Ga. The objective function of the optimization model includes a penalty term which can be adjusted by the user to control the degree of "fairness" with respect to the distribution of limited groundwater resources in the region. The decision-making framework incorporates hydrologically, politically, and economically motivated multiple conflicting objectives into the evaluation process. Results of the coupled simulation-optimization model are used to determine individual satisfaction degrees of each management strategy with respect to multiple objectives. Based on this outcome, an overall performance value is calculated by using the ordered weighted averaging (OWA) operator and the management strategy with the highest overall performance is identified as the best strategy. The OWA operator is an averaging operator that avoids ruling out some alternatives in favor of others which is observed in the logical operators such as "and" and "or." When combined with expert knowledge to identify the appropriate membership functions for the fuzzy objectives, the procedure developed in this study may yield transparent and robust groundwater management solutions in coastal aquifers.