Appendix 6. Water quality

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1. Water quality

The WFD water quality standards for rivers covered by the above report include Biological Oxygen Demand (BOD), Dissolved Oxygen (DO), Ammonia, pH and Phosphorus. Ecological status class is recorded on the scale of high, good, moderate, poor or bad. High denotes largely undisturbed conditions and the other classes represent increasing deviation from this undisturbed, or reference, condition. The ecological status classification for the water body is determined by the worst scoring quality element.

Table A6.1: Basic Typology for Rivers

Where the resulting standards for types turned out to be similar, the types were amalgamated. In each case the standards for combined types were then produced by combining their sets of data and performing the analysis on the combined set. This process allowed the simplification of the typology into two types, as shown in Table A6.2 for dissolved oxygen and ammonia.

Table A6.2: Typology for Oxygen and Ammonia for rivers

There are a number of other quality standards. Tables A6.3 for BOD and DO, A6.4 and A6.5 show the EC Freshwater Fisheries Directive Standards.

Organic micro-pollutants may also need to be considered in some cases. These substances, often derived from pharmaceuticals and hormone analogues, have been found to produce effects in aquatic species even when at extremely low concentrations. They require specialist methods to detect, but may be worth investigating in cases where no other water quality elements monitored as standard would appear to be responsible for limiting ecological status or producing strange pathological phenomena, particularly in vertebrates.

2. References

Northern Ireland Environment Agency (2009)
Water Management: Chemical Monitoring leaflet, 4pp.