The main river network in Northern Ireland has been monitored regularly for more than 30 years. Rivers are monitored both chemically (since early 1970s) and biologically (since 1990s), to assess their water quality and their level of compliance with a range of national standards, European Union (EU) Directives and international agreements.
From the early 1990s, NIEA and its predecessors classified rivers using the general quality assessment scheme (GQA), which was used throughout the UK. Since the publication of the river basin management plans in December 2008, GQA has been superseded by Water Framework Directive (WFD) classification.
WFD classification is substantially different from previous freshwater classification systems in a number of ways including:
- classification is based around water bodies which are units of area based around river confluences and larger lakes
- biological, chemical and physical quality elements monitored are combined to produce an overall classification
- there has been a considerable increase in the number of quality elements monitored
- it introduces a formal classification system for lakes