eNewsletter #13
July 2010
Water Pollution
The region’s waterways have been in the news recently and our idea of what we want our rivers and streams to look like is changing. The problem is, you can’t tell what the water is like just by looking at it. The Waiwhetu Stream in Lower Hutt looked rather nice even when it was the most polluted in the country, while other streams may look bad but are OK most of the time.
We’re often told that the water pollution problem is obvious – some irresponsible person or organisation has allowed effluent (poo and other yucky stuff) to run into the water. If only it were that simple. A lot of pollution comes in a form that is difficult to see and difficult to trace. It seeps through the ground, sneaks down the gutter and we all contribute to it in different ways. We almost all ignore this pollution when we see it, too. But that is changing – people are saying they have had enough.
Let’s be quite clear – we’re not talking about litter here. Pollution is something that affects the physical nature, chemistry and biology of waterways. Put simply, it affects the places where water animals and plants live, even making some places uninhabitable.
Pollution may be attached to small particles, such as sand or mud floating in the water column or lying on the streambed. It can also be found dissolved in or sitting on the surface of the water. Plus, it affects the animals (including people) that drink the water and eat the food that grows in it.
Save the drain for the rain
One type of pollution is sewage and it can get into our waterways by way of cross-connected pipes at our homes. The pipes that collect rainwater from your roof and yard are connected to a network of underground pipes that transfer the rainwater to local streams or seashore. These pipes are the stormwater system. There is a separate system of pipes that transfer wastewater from the toilet, bathroom, kitchen and laundry to a sewage treatment plant. These pipes are the sewerage system. Cross-connection is when these two pipes systems “connect”.
It is illegal for stormwater to go into sewers. If there is a lot of rain going into the sewer it can overflow onto the road and then carry the sewage down the gutter into the stream.
It is illegal for anything other than rainwater to go into the stormwater system. If wastewater or other liquid household wastes, such as paint, get into the stormwater drain, they will pollute streams, underground water stores and the sea.
Check that rainwater pipes around your house do not go into the sewer.
Water pollution and the workplace
There are many things you can do while at work that will prevent water pollution. The waste water that runs off a vehicle when it is being washed contains a range of substances that pollute the environment. Commercial car washes treat this waste water before disposing of it into the sewer system.
Leftover chemicals and waste products can also be a problem if they are washed into the stormwater system. To report an incident, phone the Greater Wellington environmental protection team on 0800 496 734. You’ll need to provide your name, address and phone number but these details will remain absolutely confidential.
And the humble workplace ashtray? If you use it, why not empty it when it is full? Cigarette butts are toxic to many freshwater animals so it is good to empty the ashtray to prevent them from falling onto the ground and ending up down the drain.
Soil and water
Good soil grows good food but it needs to stay on the bank, not in the stream.
One of the biggest water pollution problems is the amount of dirt and gravel washing downstream. “But that is normal” I hear you cry. Well, yes and no. It is true that New Zealand is an exciting land of earthquakes, floods and landslides and that these types of disturbance are natural and unavoidable.
What isn’t natural is frequent or ongoing disturbance caused by earthworks and vegetation clearance. Any sediment in streams adds nutrients to the water, forms chemical bonds with pollutants, smothers animals and plants, prevents fish from feeding and fills in estuaries.
So we want to reduce the amount of sediment we put into rivers by keeping all animals out of the water and off stream banks, reducing run-off into streams and giving streams plenty of room to move. Many of the region’s soils took thousands of years to develop under native forest and cannot be replaced once they have washed away.
Anybody home?
The region’s rivers, lakes and wetlands are home to 22 species of native fish and many more species of aquatic insects, such as the stonefly nymph in the photo. Even a tiny stream in your local bush reserve probably has native fish in it.
Recently, a type of fish called banded kokopu was found in small Wellington inner-city streams in Mt Cook and Aro Valley. They had migrated through up to 2km of stormwater pipes to get there. So why is it that we don’t usually see them? It’s not because they are small, they are commonly about 15cm long and can grow to 25cm. No, the reason is that most fish hide during the day and come out to feed at night.
Having good water quality ensures that the fish, and the insects they live on, will still be there in the future. After all, five of the species that migrate to and from the sea make up the whitebait run.
What is Greater Wellington doing?
Greater Wellington monitors river and stream water quality monthly at 56 sites across the region. The poorest water quality is recorded in agricultural and urban areas. These are the areas targeted for advice to landowners about streamside management. Twenty-five care groups are also supported to improve streamside and wetland environments.
Greater Wellington’s Environmental Protection Team manages pollution via a 24-hour, 7-day incident response service, site inspections and targeted investigations. The two main roles of the team are:
- Responding to and investigating environmental incidents
- Preventing pollution through special projects and proactive monitoring
Contact them on 0800 496 734 if you see pollution in a river or stream.
News
What’s your view about our environment? Greater Wellington is currently running a series of workshops so that you can tell us what you think about the future of our air, waterways, coasts, soils and biodiversity.
These natural resources underpin our quality of life. It’s vital we hear your views about their use, development and protection. Join us for a discussion and a cup of tea at a place near you.
Did you know?
Concrete waste water is extremely toxic to stream life. It attacks sensitive membranes, such as gills and skin, causing fatal burns. In 2007, a pollution incident in Auckland involving concrete wash claimed the lives of 51 eels, including one weighing more than 5kg and thought to be 60 years old. When working on projects at home, keep all concrete slurry contained on your property and protect stream life.
Useful links
Aquatic life declines at early stages of urban development
Wellington region river and stream health