Historical Monitoring Results for Rivers
Details about the GQA chemical and biological classification system and historical results can be found under the relevant headings below.
General Quality Assessment (GQA)Until 2007 chemical and biological river quality was classified each year using the General Quality Assessment Scheme (GQA).
ChemicalChemical quality was assessed by monitoring Biochemical Oxygen Demand (BOD), Dissolved Oxygen (DO) and Ammonia.
A 6-band system ranging from 'Very Good' to 'Bad' was used to describe water quality. Monitoring results for three-year sampling periods were used. This means, for example, the GQA chemical classification for 2007 was based on a combination of the results from 2005, 2006 and 2007.
- GQA chemical classification - a detailed explanation of the system
- Maps of GQA chemical classifications from 2004 to 2007 (.PDF 1.21Mb)
- Table of GQA chemical classifications from 2004 to 2007 (.PDF 117Kb)
Biological classification was based on a comparison of the macro-invertebrate fauna (animals without a backbone visible to the naked eye ) found at a sampling site with what would be expected to be found at a site without pollution. The closer the two are the better the biological class of the river. A 6-band system ranging from 'Very Good' to 'Bad' was used to describe water quality.