Water Ecology and Monitoring

When we talk about the quality of our rivers lakes and coastal waters, what exactly do we mean?  At what stage do the discharges to our waters start to do damage to the wildlife or make it unsafe for humans? How can we measure this reliably?  The Water Framework Directive has been the driver behind significant development in the science of measuring the health of our waters.

The ecology of a river lake or bay is the total environment and life there – all the plants and animals, with all their various interactions with each other and the natural environment.  Up until recently, conventional science measured the health of a river or lake solely by its ‘water quality’, tested using chemical water sampling.  Water samples were taken and tested in the lab for various chemical and physical properties; concentrations of Phosphorous or dissolved oxygen, for example.

For the first time in European legislation, the WFD recognised that the health of a body of water involves a much wider picture and so focuses on ‘water status’ as opposed to chemical water quality.   This means that, in addition to the chemical water quality, it also required the ecological health of the river or lake to be measured by examining the abundance and diversity of the animal and plant communities, in addition to the physical state of the waterway – Are natural banks still in place or have they been altered in a way that will affect the ecology?  Are levels and flow volumes sufficient to support wildlife.  This new approach, welcomed by the scientific community is a much broader measure of the overall health of a body of water.

Under the Directive, waters are classified as High; Good; Moderate; Poor or Bad, depending on their deviation from what the waterbody should be under natural conditions.  ‘Good status’ is defined as ecological conditions which deviate only slightly from those found under undisturbed conditions. Only waters classified as having ‘high’ or ‘good’ status pass the WFD test.

The quality parameters which dictate whether or not we pass that test are set out in full in Schedule 4 of the Surface Water Regulations 2009, which sets in Irish law the standards and objectives of the Water Framework Directive.  To give a sense how comprehensive this new classification and monitoring system, the following is a summary of the parameters and elements which must be monitored and assessed from now on under the Directive:


  • Composition and abundance of aquatic flora
  • Composition, abundance and biomass of phytoplankton (lakes)
  • Composition and abundance of benthic invertebrate fauna (insects and other bugs found on bed of the river)
  • Composition, abundance & age structure of fish


  • General conditions – Thermal conditions; oxygen concentration; salinity; acidification; nutrient levels (phosphorus and nitrogen); transparency (lakes)
  • Pollution with specific pollutants listed in the Surface Water Regulations 2009


These are more complex and are set out in table 6: “The hydromorphological quality elements supporting the biological quality elements” of the Surface Water Regulations 2009, page 34.

This new ‘whole ecology’ approach is a dramatic departure from the old system which focused primarily on water chemistry and it is extremely complex and poses significant technical, scientific and resource challenges.  The EPA has designed the new WFD monitoring system for Ireland incorporating all of these elements and you can read about this programme and other EPA water monitoring activities here. It also discusses some of the challenges involved, although not with the clarity which SWAN would like to see.  The new monitoring regime has been in place now since 2008, apart from coastal and transitional waters, which were late and put in place in  2010.  The latest EPA Water Quality in Ireland report, which covers the period 2007-2009 presents some of the results from this monitoring and a number of Integrated Water Quality Assessment Reports from 2013 present more up to date results for the Western River Basin District; the South Eastern River Basin District and the North Western and Neagh Bann River Basin Districts.  The new national Water Quality report for the years 2010-2012 will be publicly available in 2014 and this will be a good opportunity to review progress and engage in public discussion on the challenges and knowledge gaps in the new ‘whole ecology’ monitoring system.