Water Science & Technology Vol 21 No 2 pp 123–127 © IWA Publishing 1989

A New Form of Water Quality Index for Rivers and Streams

David G. Smith

To assist in the dissemination of water quality information to lay-people in particular, four suitability-for-use water quality indexes have been developed. The water uses are: General, Bathing, Supply, and Fish Spawning although in the Bathing and Supply Indexes protection of aquatic life is also considered. To ensure that they tell us something useful and do not ‘hide’ important information as current indexing systems tend to do, the Minimum Operator has been employed as the sub-index aggregation mechanism. This is a robust, sensible, and flexible method and seems more appropriate for this type of index than the more commonly used techniques (e.g. additive and multiplicative). Index development has been keyed into proposed New Zealand water legislation although this is not a pre-requisite for their use.

Keywords: Water quality, index, water quality index, water use, environmental management.

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