Rain is great. It helps our gardens to grow, fills our water tanks and keeps our creeks and rivers healthy – it sustains life on Earth. Rain is one part of the water cycle, a process that starts when water evaporates from the oceans on hot days and moves into the clouds as water vapour. When the air cools down, the water in the clouds also cools, and as it does so, the water vapour condenses into tiny droplets of water. The tiny droplets are attracted to one another, and when they get large enough they become too heavy to stay up in the air - they fall on us as rain. Large storms bring a lot of rain, and while some of the rainwater seeps into the ground, some of the water flows over the surface of the ground. This is stormwater, and it’s not all bad!
Out in the bush, in the natural landscape, the water cycle continues as it always has done. Much of the rainwater that falls on the land seeps into the soil, and is used by trees or other plants whose roots are constantly growing in search of the precious water. If the rain is heavy, not all the rain soaks into the ground, and water that stays on the surface becomes stormwater. Stormwater flows over the land’s surface joining streams, rivers, wetlands, and eventually returning to the sea to begin the water cycle over again.
In our towns and cities, and in some farming areas it’s a different story. In these places we have changed the landscape considerably, and these changes have a huge impact on the water cycle and on stormwater. By covering the ground with roads or pavement, clearing vegetation for development or farmland, or by planting exotic plants, we prevent a lot of the rainwater from seeping into the ground. We create more stormwater, and as it flows over these new surfaces it collects anything that we leave around. As stormwater runs across roads it picks up spilled oil, engine fluids and tyre particles; it carries away waste from our pets or farm animals; it collects rubbish from the streets; it washes excess fertilisers and pesticides from our backyards or off farm paddocks; it washes loose soil from construction sites, newly tilled paddocks or from areas where natural vegetation is cleared. Stormwater in the urban environment flows in greater quantities, and is laden with a cocktail of pollutants. 
Stormwater drains are often covered by a metal grill and can be found on the edge of most streets. Not many people realise that stormwater is not treated before reaching our waterways, so changes to stormwater that cause pollution are bad for our environment. When the pollutants in stormwater are carried into our creeks, rivers, wetlands, estuaries and out to sea, they create problems for the plants and animals that live in these ecosystems:
- When fertilisers and animal waste from our backyards, or from farms, are washed into creeks or rivers, they encourage the growth of algae. Algae clog up the waterway and use all the oxygen in the water, so animals like fish and yabbies can no longer breathe. This is called eutrophication. It also causes a bad smell and is unhealthy for humans.
- Pesticides used to kill weeds on farms and in our backyards can also kill native water plants like seagrass and mangroves. Water plants create habitat for animals, and without them the animals might die or move away.
- Stormwater flowing through our streets can pick up and carry away any rubbish that we don’t put in the bin. When this rubbish is washed into creeks or onto our beaches it not only looks horrible, but rubbish like plastic bags are known to kill sea turtles, who often mistake them for jellyfish and try to eat them.
These are just a few of the environmental problems that polluted stormwater can cause – the information sheets on this website provide more detail on some of the main stormwater pollution problems in the Burnett-Mary region.
We don’t want to stop building towns, making roads or farming, so we need to understand how stormwater works, and do everything we can to minimise the amount of pollution that gets into stormwater. These information sheets also provide some tips on how we can all reduce stormwater pollution.
