Urban rivers are generally the most polluted waterways in New Zealand. These river catchments include built-up areas with lots of people and industries. The water flows tend to be slower, and there is often little vegetation to shade the water.
As the number of people in urban areas continues to grow, more infill housing is built. This is one solution to avoid urban sprawl and the loss of productive land that often surround towns and cities. The downside is that intensification creates hard surfaces like roofs and driveways and removes the green spaces where rainwater naturally filters through the soil. Instead, the water runs into stormwater drains. These drains usually empty into small streams that are tributaries to larger streams and rivers, which eventually run to the sea.
Urban pollution sources
There are a number of ways that pollutants enter into urban waterways. Wastewater from faulty and ageing sewer systems is a major source of pollution. Other sources come from water that enters storm drains. This includes:
- oil and heavy metals from road surfaces, tyres and brake pads
- run-off from fertilisers or other lawn treatments
- bacteria and other pathogens from animal poo
- accidental spills from industrial facilities
- sediment from roadworks and land developments
- cigarette butts and other rubbish.
On a national level, the Ministry for the Environment set up the Urban Water Working Group. The group has developed 10 principles to help decision making and to promote the creation of water-sensitive urban spaces. Land Air Water Aotearoa (LAWA) is a partnership between New Zealand agencies to monitor and provide up-to-date environmental information.
Local and regional councils provide support and regulate practices that prevent contaminated water from running off hard surfaces and into waterways. Next time you are at a petrol station, look for special drains that divert water to a sanitary sewer rather than a stormwater drain. The business will probably have a special spill kit with drain covers and absorbents to blot up contaminants.
Closer to home, there are several things we can do to help with water quality. Conserving water is a good place to start. Shorter showers and using the washing machine for a full load of clothes rather than lots of small loads means less wastewater moving through the system. Sweep up spills, lawn trimmings or dirt around the home rather than hosing it into the street. Wash your car or boat on the lawn so the soapy water and dirt filters through the soil instead of running into storm drains.
Landcare groups are local people who work together to take action on local environmental issues. A common focus is riparian planting to enhance water quality and restore biodiversity. Riparian planting helps water quality in several ways:
- Plants hold the stream banks in place and prevent erosion.
- Plants slow run-off water, capture sediment and allow water to filter through the soil where soil organisms can take up nutrients and begin to break down contaminants.
- Plants shade the water and provide food for native fish and invertebrates.
The Fairfield Project is an example of taking action to support water quality and the local environment. The project is set in the Kukutāruhe gully system in Hamilton. A stream running through the site is home to endangered giant kōkopu – along with lots of weeds and rubbish. The gully is being transformed by the community with the help of local schools. Students have a dream of seeing native birds thrive in the gully so they are planting the stream edges and monitoring and trapping pests. The Fairfield Project has also established a community garden, orchard and nursery.
The Fairfield Project has created education opportunities for anyone connected with our kaupapa. It is about the experience.Lyn Rogers, The Fairfield Project
The Fairfield Project has a point of difference to many landcare groups. It is also an educational enterprise. The Kukutāruhe Gully system is used as an outdoor classroom to study the connections between terrestrial and aquatic ecosystems.
The article Water quality looks at some of the factors that affect water quality, including where the water comes from, what is in the environment in the collection area and how it is treated for human consumption.
Combine this with the article Native fish in the city to discover some of the biggest barriers to stream and native fish health in our urban areas and what we can do to help.
Use the article Exploring groundwater and pollution to find out how a year 3 class undertook an inquiry into the Waikato River and water pollution.
Research the effect of common pollutants on our waterways and hold a mock trial to determine the worst pollutant in the country in Water pollutants on trial.
In Groundwater contamination, students build an aquifer model to look at point source and non-point source pollution.
In Constructing an aquifer model, students build an aquifer model and examine how water gets into the aquifer system.
LAWA (Land, Air, Water Aotearoa) is a partnership between New Zealand’s regional councils and many others to provide information on freshwater and beach water quality, freshwater quantity, air quality and land cover. Use it to find out about water quality and swimmability in your local area.
Ministry for the Environment has information on how you can look after water in your community.
This article has been developed in partnership with the Waikato Regional Council as part of the Rivers and Us resource.