What Affects River Health?
Ever since European settlement, humans have impacted on the health of our rivers and creeks. In the mid-1800s Melbourne’s rivers and creeks were often used as a dumping ground for waste from homes and industry.
Today, stormwater pollution is the biggest problem facing our rivers and creeks. Each year about 500 billion litres of water containing litter and other harmful pollutants enters our rivers, creeks and bays via stormwater drains.
Litter
Litter is the most obvious component of stormwater pollution. When it rains, litter gets washed from streets and buildings down stormwater drains and into our rivers and creeks.
Litter is not only ugly, it also threatens animals, plants and fish living in our waterways.
Parks Victoria operates 13 litter traps on the Yarra River and 1 on the Maribyrnong. They collect about 1500 cubic metres of litter each year from the Yarra and Maribyrnong Rivers, and the Docklands area. This includes plastic and glass bottles, syringes, drink cartons, cigarette butts and lighters.
Pathogens
Even clean rivers contain some microorganisms. Many microorganisms are harmless, but some can cause disease in humans. These are called pathogens.
Potential sources of pathogens in our rivers and creeks include human and animal faecal waste. These enter via stormwater drains, poorly maintained septic tanks, sewage overflows and animals in the catchment.
The bacterium E. coli is an indicator of recent faecal contamination. Water quality in the Lower Yarra is monitored weekly for E. coli. As Melbourne’s sewerage system has continued to be upgraded, levels of E. coli in the Lower Yarra have fallen. But in the past decade, these levels have not changed significantly. This is an indication of water quality and catchment management works keeping pace with population growth and development.
E. coli levels in the Yarra River compare well with other urban rivers around the world.
Note: The Department of Health provides public health information for using recreational waterways safely. Visit the Department of Health website.
Toxicants
Stormwater also contains pollutants such as petroleum hydrocarbons from fuel and engine oil, and heavy metals such as zinc, lead, copper, chromium and lead. Many of these toxicants are washed off roofs and roads or come from poorly managed industrial sites.
Nitrogen
Nitrogen is a widely distributed natural element in the atmosphere and water. Although nitrogen has a vital role in providing plants and animals with food for growth, in excessive amounts or in certain compounds it causes vigorous growth of plants, including algae, which leads to reduced oxygen levels in water.
In 1996 we sponsored a CSIRO study, which recommended that the amount of nitrogen entering Port Phillip Bay from stormwater and treated effluent (from sewage treatment plants) be reduced by 1000 tonnes a year.
We are contributing to this target by building stormwater quality wetlands, which act as natural filters by removing nitrogen, litter and suspended solids from stormwater.