Measuring water quality

The ecological, physical and chemical state of Taranaki’s waterways has been monitored by the Taranaki Regional Council for more than 20 years.

Ecological health

Ecological health is the primary measure of freshwater quality. It is assessed using an internationally recognised index based on tiny animals – including insects, crustaceans, molluscs, worms and leeches – found in waterways. These creatures are called macroinvertebrates and the index is called the Macroinvertebrate Community Index, or MCI. The MCI takes account of how sensitive each creature is to the quality of the stream habitat.

The Council monitors these creatures at 57 key sites on 25 rivers and streams in Taranaki.

Physical & chemical state

Physical and chemical measurements are used to assess pressures on the health of rivers. The measures include bacteria levels, water clarity, conductivity and acidity (pH levels), nutrient levels, dissolved oxygen levels and the amount of oxygen consumed in the breakdown of organic matter. The latter measure is known as ‘biochemical oxygen demand’ or BOD, and is low in healthy rivers.

In all, there are 13 individual measures, which the Council monitors by taking regular samples at 11 sites across the region.

Algae

Algae, which scientists call periphyton, provide much food and energy for aquatic ecosystems. But excessive amounts can have adverse effects on aquatic habitats and aesthetics.

The Council regularly monitors long strands (filaments) and mats of periphyton at 21 sites.

Popular swimming spots

In addition to its year-round state of the environment monitoring, the Council monitors water quality at popular freshwater and coastal swimming spots every summer.

Bacteria levels are measured at 17 freshwater sites and cyanobacteria (blue-green algae) at nine freshwater sites, with slight variations over a three-year cycle.

Bacteria levels are also measured at 19 coastal sites, with slight variations over a three-year cycle.

Results of this monitoring are made available on the Council website as soon as samples are analysed.