Panel studies of the detectability of change in water colour and clarity induced by discharge of inorganic suspensoids to a small stream / R.J. Davies- Colley and D.G. Smith

By: Davies-Colley, R.J.
Contributor(s): Smith, D.G. (NIWA. Hamilton) | Water Quality Centre (Hamilton, N.Z.).
Series: Internal report / Water Quality Centre, Hamilton: no. 89/5Publisher: Hamilton, N.Z. : Hamilton Science Centre, 1990Description: 27 leaves : illustrations, graphs, diagrams ; 30 cm.Report number: HPW-IR--89/05Subject(s): RIPARIAN ZONES | PASTURES | NEW ZEALAND | WATER QUALITY In: Internal report / Water Quality Centre, HamiltonSummary: n spite of the aesthetic importance of turbidity in waters, apparently no studies of human detectability of turbidity changes have been made. In this study finely divided limestone (calcite) was injected into a small natural stream (flow = 349 l s-1) and the resulting changes in water appearance were monitored instrumentally. Initially the stream bed (gravel and some sand) was clearly visible at depths of 760 mm or less through water of 1.5 m visual clarity (horizontal sighting range of a black disk). the cue to increased turbidity is not complete disappearance of bed features but may be partial obscuration or "fogging out" of such features. Median detection thresholds (just noticeable differences) in terms of reduction in visual clarity below background (initially with the bed clearly visible) were 12 and 10 % for two independent panels (each with n=11) who observed the visual changes as turbidity was increased ramp-fashion. This low detection threshold represents a remarkably high human sensitivity to turbidity change that may be generally applicable to small, clear streams.
Tags from this library: No tags from this library for this title. Log in to add tags.
Item type Current location Call number Copy number Status Date due Barcode
JOURNAL JOURNAL WELLINGTON
STACK
STACK NO. 89/5 1 Available J018104

n spite of the aesthetic importance of turbidity in waters, apparently no studies of human detectability of turbidity changes have been made. In this study finely divided limestone (calcite) was injected into a small natural stream (flow = 349 l s-1) and the resulting changes in water appearance were monitored instrumentally. Initially the stream bed (gravel and some sand) was clearly visible at depths of 760 mm or less through water of 1.5 m visual clarity (horizontal sighting range of a black disk). the cue to increased turbidity is not complete disappearance of bed features but may be partial obscuration or "fogging out" of such features. Median detection thresholds (just noticeable differences) in terms of reduction in visual clarity below background (initially with the bed clearly visible) were 12 and 10 % for two independent panels (each with n=11) who observed the visual changes as turbidity was increased ramp-fashion. This low detection threshold represents a remarkably high human sensitivity to turbidity change that may be generally applicable to small, clear streams.

There are no comments on this title.

to post a comment.

Powered by Koha