River Monitoring Results

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The main arterial river network in Northern Ireland has been monitored regularly for more than 30 years. Chemical monitoring began in the early 1970s and has been complemented by biological monitoring since 1990. The length of rivers monitored has gradually increased over the years, and by the end of 2004 was approximately 5000 kilometres.

The rivers are monitored both chemically and biologically to ascertain their water quality and to assess their compliance with a range of national standards, European Union (EU) Directives and international agreements.

General Quality Assessment (GQA)

Chemical and biological river water quality is classified each year using the GQA scheme.

Chemical Classification

Chemical quality is assessed by: biochemical oxygen demand (BOD), dissolved oxygen (DO) and ammonia. There are six quality classes ranging from Very Good through Fair to Bad. Monitoring results for rolling three-year sampling periods are used. Thus, for example, the GQA chemical classification for 2003 is based on a combination of the results obtained during 2001, 2002 and 2003.

GQA chemical classification system - a detailed explanation of the system

Maps of the most recent available chemical classifications(.PDF 1.21Mb)Opens in new window.

Table of the most recent available chemical classifications(.PDF 117Kb)Opens in new window.

Biological Classification

Biological classification is based on comparison of the macroinvertebrate fauna found at a sampling site with what would be expected to be found in the absence of pollution. The closer the approximation between what is found and what would be expected to be found in the absence of pollution, the better the biological class of the river. There are six quality classes ranging from Very Good through Fair to Bad.

GQA biological classification system - a detailed explanation of the system

Maps of the most recent biological classifications available(.PDF 922Kb)Opens in new window.

Table of the most recent available Biological classifications(.PDF 148Kb)Opens in new window.

View details of biological monitoring frequency

Freshwater Fish Directive (FFD)

Under the terms of the European Commission (EC) Freshwater Fish Directive (78/659/EEC), some 4300km of rivers and canals and 20 standing waters (lakes and reservoirs) greater than 50 hectares in area have been designated as either salmonid (suitable for game fish) or cyprinid (suitable for coarse fish).

Designated waters are required to comply with quality standards set out in the Directive. Compliance is assessed annually using monitoring results for the calendar year.

Maps of the most recent Freshwater Fish Compliance available(.PDF 1.1Mb)Opens in new window.

Table of the most recent available Freshwater Fish Compliance(.PDF 110Kb)Opens in new window.