Over 1,150 rivers are monitored regularly in Ireland.  This monitoring looks at the chemical composition of the river water or else looks at the small animals that live on the river bed.   Some of these animals are very sensitive to pollution and so their abundance gives a very good indication of what the water quality has been like in the past.

Counting the types and the numbers of these animals allows rivers to be classified into the following categories;

  • Unpolluted – can be used as a source of drinking water with little treatment and supports salmon and trout.
  • Slightly polluted – somewhat enriched by the nutrients phosphorus and nitrogen and silted on the bottom.
  • Moderately polluted – enriched to a great extent by nutrients and containing organic matter such as sewage.
  • Seriously polluted – low levels of oxygen due to excessive amounts of organic waste.

River Water Quality

River water quality
Recent trends in the 13,188km channel length baseline showing the percentage of surveyed channel in the four EPA biological quality classes (EPA, 2010).

Using this simple classification scheme the most recent survey, published by the EPA in 2010, classifies Irish rivers as follows;

  • Unpolluted – 68.9% of river channel.

  • Slightly polluted – 20.7% of river channel.

  • Moderately polluted – 10.0% of river channel.

  • Seriously polluted – 0.4% of river channel.

This means that 31.1% of river channel is polluted to some extent with 10.4% moderately or seriously polluted.


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