The Georges River Catchment is one of the most highly urbanised catchments in Australia. While this means that lots of people get to experience and enjoy the river, it also means that there are many different issues that are impacting upon the health of the catchment.
There are many different aspects of our day-to-day lives that have an impact on the catchment. While each of us individually has a small effect on the health of the river, these small impacts combine throughout the whole catchment to significantly effect the health of the river.
One of the main causes of poor river health is stormwater pollution. Weeds, introduced animals and erosion also significantly contribute to an unhealthy catchment.
In urban and semi-urban areas, rain that falls on the roof of your house, or collects on paved areas like driveways, roads and footpaths is carried away through a system of pipes known as the stormwater system. Water in the stormwater system flows directly from the drains you see on streets to our creeks and rivers. In some cases the water is partially filtered and treated by stormwater treatment devices, however most of the time the water remains untreated. This means that anything that gets washed down the drains such as oil, litter and pesticides ends up in our waterways. Weeds, soil and mulch can also easily be washed away in rain.
Because of the impact that stormwater pollution can have on our rivers and beaches, water quality is often significantly worse after rain. Sometimes you may even be advised not to swim due to the health risk that stormwater pollution poses.
This ABC Catalyst Program segment describes the impacts of stormwater on water quality.
Erosion and Sedimentation
You may have noticed that many of our waterways are becoming shallower and muddier - something which may be very noticeable after rain.
When the ground is left bare by human activities including clearing, building (and related activities) and vehicle use such as 4WD's and trail bikes the soil is easily washed away when it rains. Examples of this can be seen between Sandy Point and Alfords Point as sediment from the ridges washes into Mill Creek and then into the Georges River. This erosion removes the fertile topsoil and the soil that is washed into waterways can contain plant nutrients, minerals, organic matter and seeds. It can also contain pesticides and toxic heavy metals.
When soil, sand, dust, cement, paint and building debris reach the waterways, they can:
- increase the risk of flooding;
- block drains;
- spread weeds to bushland;
- result in algal blooms;
- cause health problems for swimmers;
- smother and suffocate water plants and animals and impact on their ability to reproduce.