Measuring the health of waterways

The health of rivers, lakes, wetlands and groundwater is assessed by measuring the following.

Aquatic life

This is about finding out how many and which species are present in a body of water. This includes microbes, invertebrates, plants, fish, birds, and invasive species.


This includes measuring the size, shape and condition of the water body as well as its bed, banks and margins, riparian vegetation, and connections to groundwater.

Water quality

This is about measuring physical and chemical components of the water including any pollutants.

Water quantity

This involves measuring the volume and level of water.

Ecological processes

This is about observing interactions between species and their habitat.

Find out more in Our freshwater 2020 environmental report

Assessing extinction risks of freshwater species

The Department of Conservation uses the New Zealand Threat Classification System to assess the risk of extinction of freshwater species.

Species can be:

  • threatened: high risk of extinction in the immediate to medium term
  • at risk: not considered to be threatened but could quickly become so if declines continue or a new threat arises
  • not threatened: no current threat
  • data deficient: not enough information about the populations in New Zealand to determine the conservation status.

Expert panels determine whether or not a species is at risk based on:

  • population numbers
  • number of breeding pairs
  • past and predicted changes in population
  • pressure from human-induced effects.

Find out more in Our freshwater 2020 environmental report