After the big wet, spare a thought for the health of our waterways and the
substances that wash into them.
This is the call from Professor Peter Pollard from Griffith University’s Australian Rivers Institute, who has been researching the health of our urban creeks and rivers and the role that microbes, such as bacteria, play in the ecological health of the waters running through our backyards.
“People need to be conscious of the organic carbon pollutants such as biodegradable detergents that wash off their properties and into the nearest storm water drain ending up in the nearest creek,” he says.
“There are many ravenous aquatic bacteria in these waters which feed off the pollutants coming from houses, farms, urban allotments etc and the more they feed, the faster they respire using the oxygen dissolved in the water. As a result, oxygen is rapidly depleted from the water.
“During a storm, rivers flow rapidly with strong winds and turbulence. This keeps
the river ecosystem well aerated.
“However, when the storms abate, the floodwaters recede, the creek or river
ecosystem returns to its slow meandering path and the high rates of re-aeration will disappear. But the bacteria will continue to use the organic carbon pollutants washed into the waterway and hence, continue to use the oxygen.
“The problem is that the oxygen can be depleted to a point where the ecosystem cannot sustain life. Fish kills after heavy rains are often because the fish suffocate, not because of poisons, as many think,” says Professor Pollard.
“We don’t want organic carbon pollutants such as the so-called ‘environmentally friendly’ biodegradable detergents in our creek ecosystem; these products are designed to go to the sewerage treatment plant where they feed bacteria under controlled conditions and the cleaned water is released into the environment.
“Unfortunately, we do not yet know all the different types of these diffuse sources
of organic carbon pollutants. This is a big question we as environmental scientists
are attempting to answer.”
Professor Pollard says the problem has been exacerbated by the east coast of Australia being in the grip of La Nina which has brought the cyclones and monsoonal rains to the region since the beginning of 2011.
“Since then, this region has been drenched with billions of tonnes of water falling in our catchments. This is a global climatic phenomenon called the Southern Oscillation.”
The good news, though, says Professor Pollard is that “La Nina appears to be weakening based on NASA’s global satellite thermal images and data from Australia’s Bureau of Meterology.
“The end of this big wet will hopefully tell us much about how well we have been managing our catchments and waterways, and I’m particularly interested in the impacts of organic carbon pollution and the flows of our creeks and rivers.
“If everyone did their bit to reduce diffuse sources of pollution, we could significantly improve the health of our local waterways which mean so much to us all.”