The Ōpāwaho Heathcote River has ‘urban stream syndrome’. Who are the culprits causing this? There are many answers to this question and all of us can do something about it.
Increasing numbers of people realise that the natural environment just can’t be taken for granted. It needs our help, whether in rural or urban areas, to somehow return it to being clean and green, flourishing and nurturing all aspects of our lives. The Ōpāwaho Heathcote River is just one of the hundreds of waterways which can benefit from little actions that lots of us can do – little things that when done by lots of people will have a tangible impact on the river’s health.
The Ōpāwaho Heathcote River has ‘urban stream syndrome’ which means that the river has elevated concentrations of nutrients and contaminants, and reduced biotic richness related to lowered oxygen levels in addition to contamination. What are the culprits causing this syndrome?
Your car as a culprit – copper Your own car contributes to the river’s degradation in a number of ways. Unless you have specified copper-free brake pads to be fitted, the dust washed off your car’s wheels will contain very fine copper granules which will eventually end up in a waterway where their compounds are toxic to biotic life. We don’t spray our fruit trees with copper compounds for no reason. You can stop your car from producing copper. Copper-free brake pads are now readily available – just ask for them next time your mechanic tells you it is time to change the brake pads.
It is not so much the soap suds but the copper in the brake pad dust which is the problem being solved here.
Your car as a culprit – zinc Zinc oxide is an ingredient in car tyres; it is used to harden the rubber. As tyres wear, a fine dust of rubber is left on the road to be washed into the gutter and eventually into a waterway. The zinc compounds leach out into the water and are toxic to biotic life. You can do little about this other than use your car as infrequently as possible.
Your car as a culprit – washing When you wash your car, where does the run-off go? It is not so much the soap suds as the copper from the brake pad dust that is the issue. Prevent the runoff water from leaving your property by washing your car on a grassed area, or by using a commercial carwash which sends its runoff to the sewerage system.
Your car as a culprit – sediment If you, and other drivers, drive and/or park on the riverbank, very soon mud will be formed. The more cars using the same muddy spot, the more mud is created. When it rains, some of that mud is inevitably washed into the river. This is a minor source of sediment in the river compared to that which washes off the hills, but it is nevertheless, a contributing factor. Don’t drive or park on the riverbank.
Your roof as a culprit – zinc Most roofing is made of iron that is zinc-plated and then spray painted. That is great until the paint is attacked by UV light and washed off exposing the zinc plating. The zinc plating will very gradually oxidise and become soluble, the oxide washing off, entering your stormwater system and eventually ending up in a nearby waterway. Zinc oxides are toxic to microorganisms in water. You can minimise the issue by keeping your roof and gutters well-painted.
Your plastic as a culprit All households produce waste plastic – mostly from packaging. Reducing this waste stream to the minimum will benefit the entire planet, but in particular, reducing the amount of plastic that ends up in waterways is vital. This type of plastic pollution breaks down under UV quite quickly and these minute fragments of plastic are then ingested by water biota thus entering the food chain. Whenever you see litter lying on the ground, particularly if the litter contains plastic, pick it up and put it in a suitable bin. All litter eventually makes its way into waterways unless it is deliberately removed from the environment. Do your bit! Pick Up 5!
Your lawn as a culprit Do you spray your lawn with a product that is meant to kill weeds and feed the grass? Almost certainly most of the fertiliser that is contained in that product will not be taken up by the grass. Instead, it will be washed off the lawn by surface water or it will soak through the ground to the groundwater beneath. Either way, it will eventually end up in a nearby waterway. There, as a rich nutrient surplus to the natural needs of the river, it will encourage the growth of algae and macrophytes (water plants). These will remove oxygen from the water making it less able to sustain appropriate levels of other natural organisms that populate a stream’s natural ecosystem. Minimise areas of lawn (which require high energy inputs) and minimise any fertiliser used in your garden and lawn.
A group of residents plants a section of their riverbank under supervision of the Community Partnerships Ranger.
Your riverbank as a culprit – shade and absorption Is the riverbank near you mostly covered in grass? Perhaps you would prefer if the grass was mown and trimmed more regularly? Unfortunately, the river needs something very different from mown grass on its banks. It needs overhanging native grasses and flaxes as well as tall stands of leafy trees backing them up. These provide shade for the river which in turn keeps the water cool, reduces algae growth and helps to maintain the oxygen levels in the water. River microorganisms need cool water and shade to flourish. Help to increase the planting on your riverbank by joining a local river care community group, or get a group of like-minded residents together and start your own group to care for your riverbank.