Grading and general rules of thumb


The table below lists the overall gradings for popular swimming spots throughout the region. The gradings are based on the Microbiological Water Quality Guidelines for Marine and Freshwater Recreational Areas (2003), but have been adapted for the Manawatu-Whanganui Region after a reveiw by staff from Mid-Central Health Board Public Health Services and Horizons Regional Council. 

The gradings provide a realistic assessment of the long-term microbiological health-risks of swimming at the swimming spots.  They do not provide information about the potential health-risks to people and animals from benthic blue-green algae growths sometimes observed during summer low flow periods in some rivers.  Updated information on blue-green algae can be found on our "Summer Monitoring" web page.

The gradings are long-term indicators of water quality and should not be relied upon for day-to-day guidance at rivers and streams.  We recommend you use the following rules of thumb at freshwater swimming spots:

  • If the water looks clean and clear, and it is a sunny day, it should be safe to swim.
  • It is safest to wait three days after rain before swimming at river swimming spots.
  • If musty smelling black slimy mat-like growths are observed on river bed stones it is safest for you and your dog to avoid using the river.
Site Grade
Castlecliff Beach Good
Duddings Lake Very Good*
Foxton Beach Good
Himatangi Beach Good
Kahuterawa Stream @ Kahuterawa Reserve Good
Kai Iwi Beach Fair
Kai Iwi Stream @ Archers’ Bridge Poor
Kaikokopu Stream @ Himatangi Beach Poor
Lake Wiritoa Very Good*
Manawatu River @ Hopelands Reserve Fair*
Manawatu River @ Ashurst Domain Fair*
Manawatu River @ Albert Street Fair
Manawatu River @ Whirokino Boat Ramp Fair
Mangahao River @ Marima Domain Fair
Mangatainoka River @ S H 2 Reserve Fair*
Mowhanau Stream @ Kai Iwi Beach Poor
Ohau River @ Gladstone Reserve Good*
Ohau River @ Kimberley Reserve Good*
Ohau River @ Kirkcaldies Reserve Good*
Oroua River @ Timoana Park Fair
Pohangina River @ Totara Reserve Good
Rangitikei River @ Mangaweka Good
Rangitikei River @ Vinegar Hill Fair
Tokomaru River @ Horseshoe Bend Good
Wairarawa Stream @ Waiterere Beach Poor
Waitarere Beach Good
Whanganui River @ Cherry Grove Fair
Whanganui River @ Mosquito Point Fair
Whanganui River @ Town Bridge Fair

* Grades marked with an asterisk denote lakes and rivers where blue-green algae have been observed at potential health-risk densities. The risk is greatest after an extended period of low flows. Horizons Regional Council monitors blue-green algal densities and signage is installed if the potential for toxins becomes a concern during the summer season.

Very Good - Considered satisfactory for swimming at all times, and therefore may not require monitoring on a regular basis.
Good        - Satisfactory for swimming most of the time except following rainfall.  Water quality only takes a short time to recover (1-2 days).
Fair          - Generally satisfactory for swimming, though there are many potential sources of faecal material.  Caution should be taken during periods of rainfall, and swimming avoided if water is discoloured.  Water quality may take 3-4 days to recover.
Poor         - Generally not okay for swimming, as indicated by historical results.  Swimming should be avoided, particularlyby the very young, the very old and those with compromised innunity.  Permanent warning signs may be erected at these sites.
Very Poor  - Avoid swimming, as there are direct discharges of faecal material. Permanent signage will be erected at the beach stating that swimming is not recommended