A proposal for a new method to develop synthetic quality indices for air and water

Abstract During the last decades, several methods have been proposed to obtain synthetic indices expressing the environmental quality of natural resources. Such methods differ from each other in many characteristics (environmental parameters, normalization functions, aggregation functions) in order to be made suitable for specific situations. Moreover, these indices have been accused of leading to a loss of information because of their excessively synthetic character. A new tree-structured method is proposed to obtain synthetic quality indices for air and water. Besides the final index, several intermediate indices are computed, allowing environmental managers to have indices at different degrees of aggregation. The aggregation functions proposed in the literature are compared and the arithmetic mean is suggested for use, as it is demonstrated to be the most neutral function.