The Environment Agency monitors bathing waters – stretches of sea or lake where many people swim and paddle – to assess whether they meet the strict standards of the European Bathing Water Directive. The standards are set to protect public health and the environment from pollution.
The Environment Agency takes 20 water samples at each bathing water between May and September each year and post the information online: http://environment.data.gov.uk/bwq/profiles/
The samples are tested for certain types of bacteria: escherichia coli (E.coli) and intestinal enterococci, which are not directly harmful but indicate the presence of pollution. The bacteria are found in the intestines of animals and humans and pass through the body in poo. High levels of bacteria = poor water quality.
However, the water may be cleaner on the actual day you visit the beach, as the quality can change, particularly after heavy rain washes pollution into rivers and the sea. Look out for daily forecasts at some beaches.
Each beach is also given an annual classification. From 2015 this is based on sample results over the previous four years, e.g. 2015 results use data from 2012, 2013, 2014 and 2015. 2016 results use data from 2013 to 2016 and so on. The classifications are:
The standard is the highest, cleanest class
Generally good water quality
The water meets the minimum standards
Bathing is not advised at this beach as water quality has not met sufficient standards
If a bathing water is classed as Poor, you are advised not to bathe because samples taken over the previous four years have been affected by pollution. This does not mean the beach is closed – you can still enjoy everything the beach has to offer.
If a water sample has high levels of bacteria, analysis is done to estimate* the sources of pollution and work is planned in the area to improve water quality. When this work is significant and is expected to help improve bathing water quality, the four years of data for the annual classification starts from the time the work is completed and sample data from before the work are not included. This is called step change.
*Estimates are based on computer modelling, DNA analysis, and knowledge of the local area. The estimates can never be perfect because pollution to bathing waters changes from day to day depending on the season, the tides and the weather.