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Microbiological water quality is highly variable, being strongly influenced by local environmental conditions, including rainfall and wind patterns. This means that the bacteriological results of a water sample collected and tested on any one particular day is not necessarily indicative of water quality conditions a short time later.
In order to ascertain whether or not a site is suitable for contact recreation on any given day, the
MfE/MoH (2003) microbiological water quality guidelines for marine and freshwater recreational areas outline a risk-based assessment process for grading the suitability of marine and freshwater bathing sites for contact recreation. Each bathing site is awarded a Suitability for Recreation Grade (SFRG) based on an assessment of:
- actual water quality measurements (indicator bacteria counts) over time determined from routine summer recreational water quality monitoring at the site; and
- a qualitative assessment of the susceptibility of a bathing site to faecal contamination (e.g., from stormwater, sewage or stream outfalls, wildlife, stock, etc.)
The SFRG describes the general condition of the water at a site at any given time, based on both microbiological risk and indicator bacteria counts. This grade helps determine whether on-going monitoring is required, and provides the basis for advising people whether or not the water at a site is suitable for recreational use from a public health perspective. The risk of becoming sick from contact with the water at a site increases as the grading shifts from “very good” to “very poor”. Conditions affecting water quality will vary the most for the middle range of grades (“good”, “fair”, and “poor”). For example, the water at “good” sites will usually comply with the guidelines, but events such as high rainfall can increase the risk of microbiological contamination from run-off.
In August 2006, Greater Wellington published SFRGs for bathing sites in the Wellington region. Click on one of the following to:
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