Perception of water clarity and colour in terms of suitability for recreational use

Abstract

Undoubtedly, the clarity and colour of waters can strongly influence their use for recreation, so it is surprising that few attempts to relate suitability-for-use to these aspects of visual water quality have been published. In New Zealand, visual clarity of river waters in a national water quality network is routinely measured by 15 Water Resources Survey field parties who have become expert in the black disk visibility technique. The Water Resources Survey officers were surveyed using a Delphi technique for their opinions regarding the position of curves (response or sub-index curves) relating suitability-for-use of waters for bathing and aesthetics to black disk visibility and to water hue on the Munsell scale. The consensus curve for clarity showed that suitability for bathing changed from “marginally suitable” above 1·1 m to “suitable” above 1·6 m black disk visibility. This consensus curve agrees closely with the findings of an earlier study using a completely different method (interviews of recreational users at beaches of water-bodies having different measured clarity). The clarity curve for aesthetics was very similar to that for bathing. The consensus curve for colour shows that yellow-hued waters are poorly regarded for aesthetic reasons, whilst green-yellow waters are “marginal”; the preferred colours being green to blue (“suitable” or better).