You are here: Environmental reporting 
Fresh water Recreational water quality
Changes in coastal monitoring networks
Regional councils frequently review their recreational water quality monitoring programmes to make the best use of available resources. This includes dropping sites that have enough data (usually at least five years) to grade the sites for their suitability for recreational use. Sites are usually dropped from programmes if they either have consistently very excellent or very poor water quality for recreational use. The latter sites are only dropped once sufficient warning has been supplied to the public on potential health risks such as permanent signage warning people that water quality is unsuitable for swimming. As sites are dropped from programmes, resources can be diverted to new sites that have been identified as popular swimming spots that could have poor water quality but have not been sampled previously.
The following graph shows the number of coastal sites added or dropped from monitoring programmes between sampling seasons from 2003 to 2009. It also gives an indication of the average water quality of the sites that were added or dropped. This is important as it can affect the interpretation of overall water quality trends across all sites. For example, if the majority of sites that are added to monitoring programmes have general good water quality, and the majority of sites that are dropped from monitoring programmes have general poor water quality, then this may provide a false impression of an overall improvement of water quality.
In most of the summers that were measured, the sites that were added to regional sampling programmes had similar recreational water quality to the sites that were dropped. In the 2007–2008 and 2008–2009 summers more sites were dropped from programmes than added.
Number of coastal sites added or dropped from regional monitoring programmes and their average water quality, 2003–2009
Notes: 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 Ministry for the Environment.
The effect of these changes will be looked at further in a detailed analysis of the freshwater recreational water quality data, which will be carried out in late 2009.
Last updated: 29 July 2009
