This record is for Approval for Access product AfA161. The General Quality Assessment (GQA) Headline Indicator scheme or GQAHI (previously known as GQA) was the Environment Agency's national indicator for water quality in rivers and canals. It was designed to provide an accurate and consistent assessment of the state of water quality and how it changes over time as a national picture. These assessments were made for Biological, Chemical and Nutrients and undertaken for discrete river stretches. 4978 river stretches are included in the biology assessment which represent approximately 22,773km.
The Biology assessment gave an indicator of the overall 'health' of rivers. It describes water quality in terms of 83 groups of macroinvertebrates. Macroinvertebrates are small animals that can be seen with the naked eye. Some of these are pollution sensitive so their presence suggested better water quality. The assessment was made by carrying out a bi-yearly (Spring/Autumn) three minute active sampling with a pond net and a one-minute visual search for animals living on the surface or attached to rocks or vegetation. The number of taxa present were recorded and the Biological Monitoring Working Party score calculated. These values were then compared with values expected at a site in a similar, but totally unpolluted river. The mathematical model RIVPACS (the River Invertebrate Prediction and Classification System) was used to predict fauna in the absence of pollution. A category was assigned to the river stretch where the monitoring point was located:
A - Very Good: Biology similar to that expected for an average and unpolluted river of this size, type and location. High diversity of groups, usually with several species in each. Rare to find dominance of any one group.
B - Good: Biology falls a little short of that expected for an unpolluted river. Small reduction in the number of groups that are sensitive to pollution. Moderate increase in the number of individuals in the groups that tolerate pollution
C - Fairly Good: Biology worse than expected for an unpolluted river. Many sensitive groups absent or number of individuals reduced. Marked rise in numbers of individuals in groups that tolerate pollution.
D - Fair: Sensitive groups scarce and contains only small numbers of individuals. A range of pollution tolerant groups present, some with high numbers of individuals.
E – Poor: Biology restricted to pollution tolerant species with some groups dominant in terms of the numbers of individuals. Sensitive groups rare or absent.
F – Bad: Biology limited to a small number of very tolerant groups (such as worms, midge larvae and leeches), present in very high numbers. In the worst case, there may be no life present. Sample points represent one or many stretches; there are approximately 3270 biology sample points.
Issues to Note:
Additional attributes are added annually (2008 attributes are represented) with 2009 being the last year of the scheme. In 2007 the England GQA river network was reduced to the GQAHI river network. The data described have been amended to be consistent for all years. Attribution statement: © Environment Agency copyright and/or database right 2015. All rights reserved.