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Monitoring of coastal swimming spots

Which sites are monitored?

Regional and district councils monitor water quality at around 350 coastal sites throughout New Zealand every summer. It is impossible to monitor all recreational sites. Criteria for identifying which sites to monitor varies from region to region but is generally based on the extent of recreational use, historical knowledge of water quality in an area and the activities affecting it. The 350 monitored sites are beaches where water-based activities such as swimming, water-skiing, surfing and diving are common.

How are sites monitored?

Water samples are typically taken once a week over the summer (usually November to March) and tested for enterococci bacteria. Testing the water for all possible contaminants would be expensive and impractical. Instead, enterococci are used which do not necessarily cause human disease themselves but indicate the possible presence of other disease-causing organisms. Included in the group of disease-causing micro-organisms are bacteria, viruses and protozoa - these are present in the faeces of warm-blooded animals including wild animals such as birds, deer, possums, pigs and livestock and humans. There are other contaminants which can make recreational sites unsafe to swim at (eg, toxins from algal blooms). These other contaminants are not covered by this monitoring.

Learn more about the water quality guidelines used for coastal recreational areas.

Compliance for samples from coastal beaches is based on the ‘action’ threshold from the guidelines for contact recreation, of 280 enterococci per 100 millilitres of water sampled.

The water quality at individual sites is often reported by regional and district councils on their websites and in their annual environmental reports. When enterococci levels are higher than those recommended by the guidelines for contact recreation, councils liaise with health authorities to ensure the public is warned (by signs or other means) there is an unacceptable health risk if they enter the water.

Want to know more about monitoring in your area?

Information on recreational water quality monitoring and results in your area.

What are the public health risks?

Micro-organisms such as viruses, bacteria and protozoa, are present in all natural water bodies. Water contaminated by faecal micro-organisms may pose a human health hazard, particularly if swallowed. Everybody can be affected but small children, the elderly and people already weakened by illness or fatigue are more likely to become ill from exposure to contaminated water.

In most cases the health effects of exposure to contaminated water are minor and short-lived. The most common illnesses are those of the gastric-intestinal system, leading to symptoms like diarrhoea or vomiting, and infections of the eye, ear, nose and throat. However, there are other, potentially more harmful diseases such as giardiasis, cryptosporidiosis, campylobacteriosis and salmonellosis. Hepatitis A can be contracted from contaminants in the water and can lead to long-term health problems.

How has council data been used for national reporting?

The national data set used for this report has been compiled from weekly water quality sampling results provided by the regional councils and territorial authorities. These samples are considered to represent a snapshot of beach water quality.

The 'current situation' is based on data from 407 coastal sites, which had at least 10 samples collected over the 2007-2008 and 2008-2009 summers in total.

The 'recent trend' is based on data from about 350 coastal sites - only those where at least 10 water quality samples are taken over a single summer. The number of sites varies from year to year as regional monitoring programmes change. For example, the summer with the fewest monitored sites (342) was 2003-2004 and the summer with the most monitored sites (384) was 2005-2006.

Return to the water quality at coastal swimming spots page

Last updated: 29 July 2009