Most stormwater isn’t treated before it drains into our local waterways. It’s important to only drain rain and prevent anything nasty getting into our waterways. We need to protect our streams, rivers, lakes and coastal waters.

We need to protect our streams, rivers, lakes and coastal waters. 

In our urban environments, rainwater runs into gutters and is collected in stormwater pipes that may feed directly into the nearest waterway. Anything that goes into the drains can end up polluting our environment and poisoning fish, animals and plants. This pollution can also spoil waterways for our own use. 

The ORC is responsible for looking after our region’s natural resources, and we have rules to prevent pollution harming the environment. But it takes more than rules – we need your help to look after our waterways and make sure they are safe for swimming in and gathering kai from, as well as being healthy homes for the plants and fish that live in them. 

If you see pollution, report it!

Otago is a big region, and we rely on the public to let us know when and where you see pollution.

Call ORC's 24-hour pollution hotline straight away on 0800 800 033


Stormwater or Wastewater?

Infographic showing Wastewater: Removed from homes through drains, goes to treatment plants where pollutants are removed. Clean water is then safely disposed, protecting health and the environment.  Stormwater: Flows off roofs and paved areas, collecting pollutants. It enters waterways through outside drains, leading to pollution.


A wastewater system collects and removes wastewater from your house to a treatment plant. Treatment removes harmful bacteria, solids and other pollutants so that the water can be disposed of, either on land or out at sea, without damaging our health or the environment. 

Wastewater includes water and liquid wastes from hand basins, kitchen sinks, showers, washing machines, dishwashers and toilets. 


A stormwater system is designed to prevent flooding by collecting rainwater that runs off roofs and paved areas such as roads, parking lots and driveways. 

Stormwater isn’t pure water. As it runs over the ground and paved areas towards a drain, it picks up pollutants. So, whatever goes into the drain outside your house – whether it’s poured in intentionally or washed down with rainwater – enters our waterways without being treated. 

Some stormwater networks include mud tanks – these filter debris, vegetation and silt from the stormwater and prevent them entering our waterways. 

If we do nothing

Doing nothing could mean: 

  • An end to fishing trips and seafood dinners. Shellfish, watercress, eels and other fish can die or become contaminated by toxins washed in via stormwater. 
  • The fun we have in and on the water becomes hazardous to our health. High levels of bacteria and poisons in our lakes and harbours due to polluted stormwater run-off could make swimming, surfing and other water sports a thing of the past. 
  • Our waterways look like rubbish dumps. Streams and beaches can become blocked or littered with rubbish carried down by stormwater. This is not just unsightly but also a breeding ground for disease and bacteria. 
  • Our drinking water makes us sick. District or City Council water supply sources can become contaminated by waterways draining polluted stormwater. This makes it difficult and costly to treat our drinking water to safe levels. 

If we only drain rain

Only allowing rain to go down our drains will mean: 

  • We can eat healthy fish, free of contaminants. 
  • We can swim in our lakes, rivers and oceans without the fear of getting sick. 
  • Our waterways look clean and smell fresh. 
  • We can trust our drinking water. 


What you can do at work

What you can do at home

Note: The advice offered here is aimed at urban settings where stormwater and wastewater systems are off-site and serve many properties. It is less relevant to the on-site wastewater systems in many rural areas. 

Washing your car

What's the problem?

Washing cars and equipment on the road or in your driveway means the washwater (and all its pollutants) runs straight into the nearest stormwater drain. 

A Top Tip: 

Wash your car on the grass or a gravel area to keep runnoff out of stormwater drains. 

 What's the solution?

Household DIY

What's the problem?

If liquid paint or plaster, cleanup washwater and solvent wastes are tipped into the stormwater drain, the chemicals they contain can kill aquatic life. A little goes a long way! 

A Top Tip:

Tip water from cleaning paint brushes onto the lawn

 What's the solution?

Backyard DIY

What's the problem?

DIY clean-up activities like waterblasting and concreting create large amounts of polluted washwater that can end up in the nearest stormwater drain. When cleaning up around the home, think about keeping the environment clean too! 

A Top Tip:

Lawns, gravel and garden areas are great places to soak up and filter runnoff from backyard DIY

 What's the solution?

What you can do in your community

Check in with your local environmental community group. They may have active stormwater projects such as ‘adopt a drain’ initiatives.  

Page last updated 21 June 2024.