Indicators of water quality – introduction

Waikato Regional Council Senior Scientist Water Quality Dr Eloise Ryan provides insight into why regional councils measure water quality indicators.

Question for discussion:

• Why do you think many of the water quality guidelines are set at a national level rather than letting regional councils set their own?

Transcript

DR ELOISE RYAN

In the Waikato region, we follow national government guidelines. For example, for drinking water, there are Ministry of Health guidelines that stipulate the levels that are safe to drink. When it comes to swimming and recreation, there’s another set of guidelines by the Ministry for the Environment, and they determine how much bacteria is safe for people to swim in in our rivers and lakes and streams.

When it comes to water quality that protects our ecosystems and our aquatic life, there’s another set of guidelines, and they stipulate levels that are safe for things like nutrients and sediment and bacteria as well.

Recreational use water quality standards are all about keeping people safe, and that’s got to do with the amount of bacteria or toxic algae in the water. So that’s why the recreational water quality standards cover bacteria. The indicator bacteria we test for is called E. coli bacteria, and that occurs in the guts of warm-blooded animals, for example, humans, possums, ruminants like cows or sheep. So it’s not natural, it entered the waterway through our guts and our faeces.

We measure water clarity at the council to determine safety for swimming. For example, people don’t like swimming in water that’s full of sediment – they like to swim in nice clear water. So we measure it, and basically, if you can see less than 1.6 metres through the water, it’s not very clear and not very suitable for swimming. So we use that as part of our swimmability indicator, whereas our other water quality standards cover many other things.

So the Waikato Regional Council monitors a lot of different indicators of water quality – we monitor around 32 a month – but we look at seven different indicators to say whether the water is passable or not. And those indicators include temperature, turbidity, pH, the nutrients – total nitrogen, total phosphorus – ammonia and dissolved oxygen, because like humans, plants and animals need oxygen to breathe as well.

Acknowledgements

Dr Eloise Ryan
Aroha Salu
Alicia Caitlin
Waikato Regional Council
Footage of man fishing, Whaka Trout