Talking on Water 4: In the swim

‘Swimmability’ is a popular topic but what does it mean?

Talking on Water cartoon 4.

You can label rivers ‘unswimmable’ if bacteria are detected. But what say they’re swollen and full of fast-moving debris after big rains? No sensible person would go swimming then, regardless of bacteria levels.

Popular swimming spots should be ‘swimmable’ when people want to use them. Taranaki Regional Council monitoring shows that most of the time, they are. At the few sites where bacteria levels are persistently high, birds are the main culprits.

Swim when it makes sense

There are many different versions of what ‘swimmable’ means or should mean. Sometimes conversations get confused.

For the Taranaki Regional Council, it means that the sites where the local community goes swimming should be of good quality at the times the community wants to go swimming. 

At other times (such as during cold and wet weather, or when river flows are surging and carrying debris and sediment), there will be lots of good reasons not to go in the water. High levels of the bacteria that indicate possible faecal pollution might be one of them.

As a precautionary approach, the Council advises that you should consider not swimming in a river for up to three days after heavy rain or high flows. Be guided by common sense, your own judgment, and published information on water quality (during the summer bathing season, you can find monitoring results on this website or at link)).

Discussions continue on which system to use for classifying ‘swimmability’. The Government’s suggestion is to derive a permanent grading from data gathered year-round, under all conditions (even when it would be silly to swim), over the past 10 years or so. 

The Council, however, believes the latest and most up-to-date result is the most useful.

Incidentally, DNA testing has revealed that in Taranaki, the worst pollution at our favourite swimming spots is caused by seagulls, ducks, and pukeko.

Freshwater bathing sampling results.