Describing water quality with aggregate index

Alternative efforts to describe water quality by an aggregate index consist ing of subindices of the constituent quality variables are examined. Ambigu ity problems exist where all the subindices are acceptable and yet the over all index is not. Eclipsing problems exist where the overall index is insen sitive to a single variable; such insensitivity is unacceptable, A mathemat ical formulation is developed that avoids these problems of ambiguity and e clipsing. Furthermore, the recommended index form is open to increasing the number of variables included within the index.