Bathing water quality guidelines for marine and freshwater areas

The water sample tests results from the recreational water quality monitoring programme are assessed against the national microbiological water quality guidelines published by the Ministry for the Environment and the Ministry of Health (2003). These guidelines use bacteriological indicators associated with the gut of warm-blooded animals to assess the risk of faecal contamination and therefore the potential presence of harmful pathogens. Compliance with the guidelines should ensure that people using water for contact recreation are not exposed to significant health risks. The bacteriological indicators used are:

Freshwater (including estuarine waters): Escherichia coli (E. coli)
Marine waters: Enterococci
Recreational shellfish-gathering waters: faecal coliforms

The guidelines are "trigger" values to help water managers determine when management intervention is required. The "trigger" values underpin a three-tier management framework analogous to traffic lights.

Three-tier management framework for recreational waters advocated by MfE/MoH (2003)

Mode	Management Response
Green/Surveillance	Routine monitoring
Amber/Alert	Increased monitoring, investigation of source and risk assessment
Red/Action	Closure, public warnings, increased monitoring and investigation of source

When water quality falls in the “surveillance mode”, this indicates that the risk of illness from bathing is acceptable (19/1000 risk for marine waters and 8/1000 risk for fresh waters). If water quality falls into the “alert” category, this indicates an increased risk of illness from bathing, but still within an acceptable range. However, if the water quality enters the “action” category, then the water poses an unacceptable health risk from bathing. At this point, warning signs are erected at the bathing site, and the public is informed that it is unsafe to swim at that site.

Guideline for fresh waters

Mode	Guideline *( E. coli* count in colony-forming units (cfu) per 100 mL)**	Management Response
Green/Surveillance	Single sample ≤ 260	Routine monitoring
Amber/Alert	Single sample > 260 and ≤ 550	Increased monitoring, investigation of source and risk assessment
Red/Action	Single sample > 550	Closure, public warnings, increased monitoring and investigation of source

Guideline for marine waters

Mode	Guideline (Enterococci count in colony-forming units (cfu) per 100 mL)	Management Response
Green/Surveillance	Single sample ≤ 140	Routine monitoring
Amber/Alert	Single sample > 140	Increased monitoring, investigation of source and risk assessment
Red/Action	Two consecutive samples within 24 hours > 280	Closure, public warnings, increased monitoring and investigation of source

Cautionary note

The MfE/MoH (2003) guidelines do not cover toxic algal blooms, which in certain places under certain conditions, may pose a significant risk to contact recreation