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Compliance of water quality at freshwater swimming spots with guidelines

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Current situation

Over the 2007–2008 and 2008–2009 summers, 58 per cent of the 300 monitored freshwater 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 E. coli levels).

Eight 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 freshwater swimming spots for the 2007–2008 and 2008–2009 summers

Bacterial water quality at monitored freshwater swimming spots for the 2007–2008 and 2008–2009 summers

Text description for above map

Notes:
(1) Based on data from 300 sites that had at least 10 samples collected over the 2007–2008 and 2008–2009 summers in total. The data for these sites can be viewed in this spreadsheet.
(2) Compliance with the guidelines for contact recreation is based on the threshold of 550 E. coli 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 Ministry for the Environment.

Recent trend

These results suggest that recreational water quality at monitored freshwater 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% of sampling occasions has fluctuated between 41 and 60 per cent.

Compliance of monitored freshwater swimming spots with guidelines for contact recreation, 2003–2009

Compliance of monitored freshwater swimming spots with guidelines for contact recreation, 2003–2009

Data (text description) for above graph

Notes:
(1) Results for each summer are based on data from about 200 freshwater 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 (153) was 2003-2004 and the summer with the most monitored sites (230) was 2006-2007.
(2) Compliance with the guidelines for contact recreation is based on the threshold of 550 E. coli per 100 millilitres of water sampled.
Source: Data collected by regional, city and district councils and collated by 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 freshwater 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 lakes. Therefore, bacteria levels in the water during wet summers are often high when compared with dry summers.

Freshwater swimming spots generally have higher levels of bacteria and longer-lasting contamination events than coastal beaches. This is largely because faecal matter is more rapidly diluted and dispersed by ocean 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?

Latest recreational water quality results for freshwater sites in your area

The snapshot report on freshwater recreational water quality for 2003 to 2009 has more detail on:

  • what affects water quality
  • the associated public health risks
  • how samples are collected
  • what sites are monitored
  • accessing data for lakes and rivers 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?

Last updated: 29 June 2009