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Fresh Water Recreational water quality Snapshot
Freshwater sites
Freshwater sites are generally on rivers or lakes but include some estuaries
and lagoons with brackish (that is, partly salty and partly fresh) water.
The bacteria Escherichia coli (E. coli) is used to indicate the level of human disease risk in fresh water. Find out more about public health risk and bacteria indicators.
Water quality
Water quality is defined by the number of samples taken over a bathing season that comply with guidelines for acceptable public health risk. The higher the number of samples that comply with guidelines, the better the water quality.
Find out more about guideline limits and how water quality is monitored.
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.
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The design of water quality monitoring programmes (ie, numbers and locations of monitoring sites) may differ between regions and monitoring seasons (summers). It is dependent on a number of factors including local climatic patterns, annual weather variation, population density and resources available to the local monitoring agency.
Find out more about:
Current water quality
Bacterial water quality at monitored freshwater swimming spots for the 2007–2008 and 2008–2009 summers
The map shows the monitoring results of the 2007–2008 and 2008–2009 summers seasons for water quality in lakes and rivers for contact recreation.
The map uses a colour guide to show the proportion of samples from each testing site that comply with guidelines for safe levels of E. coli for contact recreation (ie, swimming).
The five classes are:
- not sufficiently sampled
- 95 to 100 per cent of samples comply (ie, water quality is suitable for swimming almost all the time)
- 90 to less than 95 per cent of samples comply
- 75 to less than 90 per cent of samples comply
- less than 75 per cent of samples comply (ie, water quality is often unsuitable for swimming).
The map shows that sites are distributed throughout the country with good and poor sites appearing in every region. The poorest sites generally appear close to the coast (ie, they are downstream sites in lowland areas).
View the average compliance with the guidelines for the 2007–2008 and 2008–2009 summers in this spreadsheet.
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.
Changes over time
Compliance of monitored freshwater swimming spots with guidelines for contact recreation, 2003–2009
Compliance category |
Proportion of sites in each compliance category |
|||||
|---|---|---|---|---|---|---|
2003-04 |
2004-05 |
2005-06 |
2006-07 |
2007-08 |
2008-09 |
|
95 to 100% of samples comply (water quality is suitable for swimming almost all the time) |
41% |
52% |
49% |
60% |
48% |
54% |
90 to <95% of samples comply |
22% |
16% |
22% |
13% |
20% |
18% |
75 to <90% of samples comply |
24% |
20% |
15% |
17% |
19% |
18% |
Less than 75% of samples comply (water quality is often unsuitable for swimming) |
14% |
12% |
14% |
10% |
13% |
10% |
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.
What do the results mean?
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.
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.
Individual councils may know the cause of non-compliance with guidelines at certain sites and should be contacted if you require more information on your local area.
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 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).
It is important to note that even if swimming spots are safe for recreational use in terms of bacteria levels, they may not be safe for other reasons (eg, the presence of algal toxins).
Last updated: 29 July 2009
