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Compliance of water quality at coastal swimming spots with guidelines
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Current situation
Over the 2007-2008 and 2008-2009 summers, 79 per cent of the 400-odd monitored coastal swimming spots had water quality that met the guidelines for contact recreation almost all of the time (ie, at least 95 per cent of the samples taken at these sites had safe Enterococci levels).
Two per cent of the sites breached the guidelines regularly (ie, more than 25 per cent of the samples taken from these sites were non-compliant), indicating that these sites often have poor water quality and are unsuitable for swimming.
Bacterial water quality at monitored coastal swimming spots for the 2007–2008 and 2008–2009 summers
Text description for above map
Notes:
(1) Based on data from 407 coastal sites that had at least 10 samples collected over the 2007-2008 and 2008-2009 summers in total. The data can be viewed in this spreadsheet.
(2)
Compliance with the guidelines for contact recreation for coastal sites is based on the ‘action’ threshold of 280 enterococci per 100 millilitres of water sampled.
(3) 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.
Source: Data collected by regional, city and district councils and collated by the Ministry for the Environment.
Recent trend
These results suggest that recreational water quality at monitored coastal sites has been relatively stable at a national-scale over the last six years. The number of sites with samples that met the guidelines for contact recreation on at least 95 per cent of sampling occasions has fluctuated between 65 and 80 per cent.
Compliance of monitored coastal swimming spots with guidelines for contact recreation, 2003–2009
Notes:
(1) Results for each summer are based on data from about 350 coastal sites where at least 10 water quality samples were taken. 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.
(2)
Compliance with the guidelines for contact recreation for coastal sites is based on the ‘action’ threshold of 280 enterococci per 100 millilitres of water sampled.
Source: Data collected by regional, city and district councils and collated by the Ministry for the Environment.
However, it is difficult to determine whether this is a true reflection of changes in recreational water quality, as sites added or dropped from regional monitoring programmes could mask any actual changes in water quality at a national-scale over time. These changes will be looked at further in a detailed analysis of the recreational water quality data, which will be carried out by the Ministry in late 2009.
Several natural and human factors may cause variations in water quality between seasons. For example, during a wet summer (with frequent rain) more faecal matter is carried from the land into rivers and estuaries. Therefore, bacteria levels in the water during wet summers are often high when compared with dry summers.
Coastal beaches generally have lower levels of bacteria than freshwater swimming spots. This is largely because faecal matter is more rapidly diluted and dispersed by the currents and large volumes of water at the coast.
The difference between bacteria levels at freshwater and coastal swimming spots is illustrated by comparing monitoring results for the 2007–2008 and 2008–2009 summers. The water quality of 79 per cent of monitored coastal beaches met the guidelines for swimming almost all of the time (compared with 58 per cent of freshwater sites). Two per cent of the coastal beaches breached the guidelines regularly (compared with 8 per cent of freshwater sites).
The above information has come from the snapshot report on recreational water quality and Environment New Zealand 2007.
Want to know more?
The snapshot report on coastal recreational water quality for 2003 to 2009 has more detail on:
- what affects coastal water quality
- the associated public health risks
- how samples are collected
- what sites are monitored
- accessing data for beaches in your area
- what the results mean.
Individual councils may know the cause of non-compliance with guidelines at certain sites. If you would like to know more about water quality in your area, contact your local council.
What can you do?
- Rubbish can be harmful to wildlife – 90 per cent of marine rubbish found on coasts is beverage packaging. Don't litter.
- Adopt-a-beach and take responsibility for keeping it clean by collecting rubbish regularly.
- Reduce pollution - avoid pouring waste liquids into outside drains or putting rubbish into the gutter as this can end up in the sea.
Last updated: 29 July 2009
