"This means that river users should be able to check up-to-date information before leaving home, or by smartphone at the swimming spot. The main problem with weekly sampling is that the sample is not always reflective of the water quality for the whole week, especially if it has rained."
Horizons has installed signs that offer simple ways for the public to assess water quality at popular swim spots this summer. It also has a general guideline:
"If the water looks clear and it's a sunny day you should be good to go, but if the water looks murky after recent rain then we advise people to wait until it clears before swimming."
As well as checking for E. coli at swimming places, Horizons monitors for blue-green algae slimes which can pose a risk to people and animals and cause a musty smell during extended periods of low flows.
"Again it's a judgment call on the public's part. If you see black mat-like slimy growths on stones, it is best for you and your animal to stay out of the water."
On Tuesday the Whanganui River at the Town Bridge and Castlecliff and Kai Iwi beaches were all good for swimming. The Mowhanau Stream at Kai Iwi Beach was just satisfactory, but fine for paddling. Swimming was okay at Dudding and Wiritoa lakes, but cyanobacteria levels mean they could be risky for dogs.
