Title: Biological water quality report 1996
Author: Environment Agency
Document Type: Monograph
Abstract:
The 1996 biological survey in the Anglian Region followed the same methodology and sampling network as the 1995 GQA survey. This has allowed a direct comparison to be made between 926 stretches representing 4719.6km of river length in the Region. The biological classification scheme is based on a shortfall between the macro invertebrates found at a site, and those which would be expected at that site under natural conditions of water quality. This compensates for the natural differences in biology between different river types A biological model called RIVPACS (River InVertebrate Prediction And Classification System) is used to produce a prediction of taxa present under natural conditions. The biological GQA classification scheme uses the ratios of predicted and observed values for ASPT and Number of Taxa to place a site in one of six classes, a (very good) to f (bad). As the predictions produced by RIVPACS are based on a number of parameters such as annual average alkalinity, width, depth and substrate which can vary with time, there is a danger that the predictions for a site will change over time. This would lead to a situation where the RIVPACS ‘target’ for a site constantly changes. To prevent this, the set of variables compiled for the 1995 survey were used to make a fixed prediction for each site which will be used for grading. This prediction will only be changed in the future if the site changes significantly eg due to engineering or siltation. This protocol allows a direct comparison to be made between years. If a change in grade is recorded, it is due to a change in the observed biology rather than a change in the prediction made by RIVPACS.
Publisher: Environment Agency
Publication Date: 1996
Publication Place: Peterborough
Subject Keywords: Environmental quality; Water quality; RIVPACS; Biological sampling; Rivers; Canals
Geographic Keywords: East Anglia
Extent: n.p. [19]
Permalink: http://www.environmentdata.org/archive/ealit:381
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