12 refs ; 5 figs ; 7 tables

The derivation of four suitability-for-use water quality indexes is described. They are for General, Regular Public Bathing, Water Supply and Fish Spawning (salmonid) water uses. This report presents the sub-index graphs (i.e. graphs relating sub-index scores with determined concentration) required for index calculation. The method of aggregation of sub-index scores obtained from the graphs employs the method of the Minimum Operator. This is a robust, sensible, and flexible aggregation method and uses the lowest sub-index scores as the final Index score. Comments on the use of the indexes is furnished plus the brief rules for index calculation. The strategy employed for the development of the indexes is also described. It is based on that used by the United States National Sanitation Foundation and uses Delphi iteration, although this strategy was not strictly adhered to. The selection of determinands for use in these indexes is based on standards for the proposed revision of New Zealand's water and soil legislation. At this stage the indexes are seen as interim only and require testing by water management agencies prior to final recommendation for use.