Download various types of water pollution

Increasing Salinity
There are two major causes of increasing salinity: removing native vegetation, and largescale, low efficiency irrigation systems. Both result in the water table moving closer to
the surface, bringing salt with it.
This can leave soil impossible to cultivate, render water unsuitable for drinking, stock
watering and irrigation, and kill aquatic plants and animals living in streams and
wetlands.
More information on salinity is available at the Department of Sustainability and
Environment's website (then follow the links Land and Salinity) or alternatively at
Murray Darling Basin Commission's website.
Nutrient Enrichment
All plants and animals need nutrients to grow. However, when excessive amounts of
nutrients are present, algal blooms and nuisance plant growths can occur in waterways.
This can lead to:





reduction in habitat and light availability for plants and animals
decreases in the available oxygen in the water
obstruction of waterways, affecting recreational use and fish migration
odours and an unsightly appearance
the production of toxins which threaten aquatic ecosystems and human uses of water
(for some cyanobacteria blooms)
Elevated nutrient levels in waterways, reservoirs and wetlands can be caused by
wastewater treatment plant discharges, urban stormwater runoff, irrigation drainage,
agricultural runoff, intensive animal industries, soil erosion and forestry activities.
Nutrients enter the marine environment through creeks, rivers and estuaries. Excessive
nutrient inputs from catchments to the coast can lead to imbalances to marine ecosystems.
For example the Gippsland Lakes receive high levels of nutrient inputs, which has lead to
some of the outcomes listed above.
Information on nutrients is available on the Murray Darling Basin Commission's
website.
Sedimentation
Sediment entering waterways is a natural process, but in excessive quantities it can cause
problems. Sources of sediment include:






urban development
agriculture
forestry activities
roads
industrial and wastewater discharges
housing developments
The greatest impact of sediment entering waterways is on instream habitat. Sediment can
fill pools, cover and fill in rocky bottoms and coat snags. This can reduce the available
habitat and affect the breeding and feeding habits of native fish and aquatic invertebrates
(eg. insects, snails, worms and shrimps).
Sediments suspended in the water column turn the water turbid (muddy). This reduces the
amount of sunlight entering the water, which inhibits plant growth and makes it difficult
for predators such as fish and birds to hunt. Suspended sediments in the water column
also interfere with the uptake of oxygen by fish and invertebrates.
Sediments also enter the marine environment through creeks, rivers and estuaries, again
emphasising that what we do in our catchments affects our coast. Excessive sediments
can kill marine plants and animals by smothering them or cutting off access to light.
Sedimentation is one of the factors causing the large decline in seagrass seen in recent
years in Western Port. Although some areas of seagrass are recovering, others are still
under threat and EPA is working in partnership to improve water quality.
Information on sediments is available on the Murray Darling Basin Commission's
website.
Further information about sedimentation of rivers and streams is available from the
Department of Sustainability and Environment's Plants and Animals website, by
following the links Native Plants and Animals - Freshwater Ecosystems.
Oil, Heavy Metals and Other Chemicals
Oils, heavy metals and other chemicals enter waterways from a variety of potential
sources, including urban and agricultural runoff, industrial and mining operations, landfill
leachate, and transportation or industrial spills.
These chemicals can have drastic impacts on freshwater and marine ecosystems. This
may vary in severity from reducing growth and reproduction, to directly killing plants
and animals. The effects of many toxic chemicals are increased by their ability to remain
and build up in the environment over a long period of time. The results can be
particularly destructive in wetlands and bays where flushing is limited.
More detailed information about the effects of toxic materials on aquatic ecosystems is
available from the Department of Sustainability and Environment's Plants and
Animals website, by following the links Native Plants and Animals - Freshwater
Ecosystems.
Information on chemical pollutants are available on the Murray Darling Basin
Commission's website.
The contents of this page were last edited