EU Swim Project

Water Quality

The Island of Ireland is surrounded by miles of astonishing coastline and stunning beaches, hence we rely on the sea as an important source of food, and as a place for recreational enjoyment, meaning the importance of clean water cannot be underestimated.


The quality of bathing water is measured by the amount of two types of bacteria present in a sample, these bacteria are:

  • – Escherichia coli
  • – Intestinal enterococci


Increases in the concentration of these two types of bacteria indicate a decrease in bathing water quality.

Both of these bacteria are present in the intestines of animals and humans, and can be potentially harmful to human health. Bathers, who swim in an area with poor water quality can be susceptible to illnesses, such as gastroenteritis and ear infections.



Potentially harmful levels of bacteria can be caused by factors such as heavy rainfall, washing faecal material from sewage systems, urban drainage or agricultural sources, into the sea, via streams and rivers.

Other sources of contamination can come from:

  • Wrongly connected sewage pipes, which happen when domestic plumbing has been connected into surface water drains instead of the foul sewer; further information and advice on this can be found at connect right


  • Failed septic tank systems due to aging or lack of maintenance, poses risks to surface and ground waters quality; to find out more visit The James Hutton Institute 



  • Pet owners failing to pick up after their dog has fouled on the beach, or close to a drain



  • Wildlife, such as, a large number of birds fouling in a small area, on, or near a beach, and overcrowded beaches with many swimmers in a small area



Years when sunlight is below average can see a decrease in water quality, as the sun’s ultraviolet rays are able to kill bacteria found in bathing water.

In 1975, the first European bathing water legislation, the ‘Bathing Water Directive’ was introduced to protect and improve bathing water quality, with the aim of safeguarding human health and facilitating recreational use of natural waters; it was later replaced by the 2006 ‘New Bathing Water Directive’, which incorporates stricter standards along with simplified management and surveillance methods.

Each year, designated bathing water sites receive a water quality classification; they are classified as either:

Poor – the water has not met the minimum standards

Sufficient – the water meets minimum standards

Good – generally good water quality

Excellent – the highest, cleanest class


The ‘official’ bathing season, runs from mid-May to the end of September, during this time bathing water samples are collected, tested in a laboratory and results released, on generally, a weekly basis.

However, water quality can change within a matter of hours, so weekly manual testing may not be enough to protect human health; the EU SWIM Project is developing a computer model, that uses weather variables, such as rainfall, to provide accurate water quality predictions, and these predictions will be communicated to the public, via a free app, social media channels, our website and electronic beach signs.



During the months outside of the bathing season, the computer model is not designed to make water quality predictions, as weather variables dramatically change with the arrival of winter. At these times, the electronic signage will be used by the project, in conjunction with relevant councils, to display relevant local messages.

For example, one of our electronic signs is located at a beach frequently used by horse-riders, the sign reads a message requesting that “riders please clean-up after their horses”; therefore, the signs will help to keep EU SWIM beaches usable and safe, for all beach users, throughout the year.

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