Extent of the problem

Pollution affects almost all rivers, many aquifers and some lakes in Aotearoa New Zealand. It is higher in stretches of waterways surrounded by urban development, farming, and forestry than those with native forest. 

It can threaten the health of freshwater species and habitats. It can also affect our health, cultural wellbeing, practices, and knowledge.

To reduce pollution in waterways we need to make changes to the way we live. We also need to invest in addressing the issues.

Types of pollutants

Our waterways are polluted by:

  • nutrients (eg, nitrogen and phosphorous applied as fertiliser)
  • pathogens which are disease-causing microorganisms (eg, Campylobacter) 
  • sediment (eg, from soil erosion)
  • heavy metals (eg, copper and zinc when washed into freshwater from cities and towns)

Find out more in Our freshwater 2020 environmental report

How pollutants impact water quality and freshwater species

Sediment

When sediment enters freshwater it can make it cloudy and degrade water quality. It can smother the habitats of freshwater species on the bottoms and banks of rivers and lakes.

Sediment enters waterways when:

  • soil is eroded by livestock or heavy rain
  • soil is compacted (eg, by livestock or machinery) - compaction decreases the ability of soil to hold water
  • trees are clear felled (eg, during forestry)
  • there is a lack of riverside planting to reduce soil erosion and run-off of pollutants from the land.

Nutrients

Excess nutrients in freshwater can cause algal blooms (a rapid growth of microscopic algae or cyanobacteria). This often shows up as a coloured scum on the water's surface. Algal blooms degrade water quality.

Nutrients can enter waterways when:

  • land is converted to pasture
  • too much fertiliser is applied to the land
  • effluent from livestock ends up in waterways.

Pathogens 

Pathogens (eg, ecoli) are disease causing organisms which can threaten freshwater species. They can also make people ill when they drink or swim in polluted water. 

Sources of pathogens in waterways are:

  • wastewater discharges, leaks and overflows
  • algae blooms
  • run-off from livestock farming. 

Heavy metals

Heavy metals can threaten the health of freshwater species. They can also accumulate in their bodies making them unsafe for us to eat.

Heavy metals can make their way into waterways from:

  • industry and urban areas 
  • road traffic. 
Our activities are polluting the freshwater environment. Infographic.
This infographic illustrates the sources and effects of pollutants in freshwater.
Our activities are polluting the freshwater environment. Infographic.
This infographic illustrates the sources and effects of pollutants in freshwater.