Point and non-point source pollution
Pollution enters water from two types of source: point and non-point.
Point source pollution comes from readily identifiable sources
such as industrial pipes. Significant discharges are controlled
by an EPA managed licensing system. The licences control the kind,
and volume, of pollutant allowed to be released into a waterway.
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Point
source pollution
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Non-point
source pollution
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Non-point source (NPS), or diffuse, pollution means pollution
not covered by an EPA licence. It occurs over a wide area and
is associated with a particular land use. Major forms of NPS include
seepage from septic tanks, sediment run off from construction
sites, and pesticides and fertilisers from agricultural operations.
One way the community, business and industry can reduce the amount
of pollution produced is to turn waste into
resources.
Pollution by urban stormwater
 Urban
stormwater is runoff from buildings, streets and footpaths. It
includes flows during and following rain, as well as dry-weather
flows which come from garden watering, wash downs and illegal
discharges.
The stormwater system is different from the sewerage system (or
septic tank) that services the kitchen, laundry, toilet and bathroom
drains. The sewerage system treats the water before it is piped
out to sea or used for irrigation. Stormwater is NOT treated before
it enters our waterways.
Stormwater can contain litter, dust, soil, oil and grease from
roads, garden waste, chemicals, and nutrients from animal faeces
and fertilisers. This pollution can kill fish, make water unsafe
for swimming, entangle aquatic animals in rubbish, and release
toxins.
Clean stormwater is increasingly being seen as a valuable resource
in a state where rainfall is low and reliance on the ailing River
Murray is high. However, if we are to use this resource we need
to prevent stormwater pollution.
The State Government has recently introduced an Environment
Protection (Water Quality) Policy to encourage the re-use
of stormwater. It includes fines for people who deliberately or
accidentally pollute stormwater. Check out Easy
ways to clean water.
Nutrient enrichment
 Nutrients
can accumulate in waters naturally and increase aquatic plant
growth. However, human activities can accelerate this process,
and create excessive nutrient loads (eutrophication) in lakes,
rivers, harbours and estuaries. Nutrients from human activities
include sewage effluent, urban stormwater,
artificial fertiliser run off, sediment,
stock manure, nutrients leached from soil, winery waste, and aquaculture.
An increase in nutrients (nitrogen and phosphorus) results in
an increase in the growth of algae. In this environment algae
often multiply quickly to dominate an ecosystem and create a bloom.
Algal blooms can have many different and adverse effects on an
ecosystem. Blooms can smother aquatic plants and compete for light
and space. When they die they decompose, a process which reduces
the amount of oxygen in the water, killing fish.
Some blue green algae (cyanobacteria) release toxins when they
die. This has been a major problem in the River
Murray, where it has killed fish and poisoned stock water.
Blue green algae are also a health hazard for humans who come
into contact with the water. They can cause skin irritation, swollen
lips, eye soreness, earache, and asthma.
Nutrient enrichment of Gulf St Vincent has resulted in an increase
in algae that attach themselves to other aquatic plants for support
(epiphytic algae). Epiphytic
algae have resulted in the loss of over 6000 hectares of seagrass
between Port Gawler and Aldinga. Loss of seagrass has led to more
sediment in our coastal waters, an increase in coastal erosion,
and a dramatic loss of biodiversity in sub-tidal reefs.
In the Port River, nutrient enrichment from urban stormwater
and industry turns the water red-brown. The discolouration, known
as a 'red tide', is due to an algal bloom which can produce toxins
that cause severe gastro-intestinal and neurological illnesses
such as paralytic shellfish poisoning (PSP).
Algal blooms can force water restrictions and the closure of
waterways to fishing, swimming and boating. They can kill fish
and increase costs to agriculture, tourism and water authorities.
It has been estimated that algal blooms cost Australia $150m a
year (Land and Water Resources Development Commission, 1999).
Sedimentation
Sedimentation occurs when mineral and
organic particles are transported from their place of origin by
water, wind, gravity, or ice. This process occurs naturally; but
human activities can accelerate it, causing unnaturally high levels
of sediment in our rivers, lakes and streams.
Human activities that increase sedimentation include:
- land clearance, which can lead to gully erosion
- poorly managed building sites, which allow soil and other
pollutants to enter the stormwater system
- unsealed roads near waterways
- uncontrolled stock access to streams and rivers, which increases
erosion of river banks
- construction of dams and reservoirs.
Sediments carry nutrients
which reduce water quality and promote algal blooms. Increased
sedimentation leads to greater turbidity in our waterways, in-filling
of creek pools, and weed growth. High levels of sedimentation
can also smother plants, suffocate fish, and make habitats unsuitable
for native wildlife.
Landholders can reduce sedimentation by fencing off their streams
and rivers from stock, and revegetating riparian zones. Contact
your local catchment water management board for advice and possible
funding support. Builders and developers can check out a range
of EPA publications for advice on how to
comply with current legislation
and protect water quality.
Oils, heavy metals and other chemicals
Pollutants such as oils, heavy metals and chemicals can cause
substantial environmental damage. They often contaminate the stormwater
system that flows untreated into natural waterways. Sources of
pollution include:
- leaking cars
- fuel stations and mechanical repair shops
- auto dismantlers and crash repairers
- auto services
- paint
- batteries
- timber treating works
- leather tanning works
- carpet cleaning
- air-conditioning refrigerants
- pesticides and fertilisers
Oil and grease are toxic to animals and plants and form a film
on the water surface, making it difficult for organisms to breath.
Heavy metals such as cadmium, chromium, copper, zinc and lead
are also toxic. These substances can accumulate in aquatic animals
such as mussels and have a dangerous flow-on through the food
chain.
For tips on the correct disposal or storage of these substances
see the EPA publications or visit the stormwater
pollution prevention projects web
page.
Other impacts on the water environment
The health of the state's rivers, streams, lakes and reservoirs,
and marine waters can be affected by a number of other sources
including acid rain (108KB
PDF) and bushfires.
This page was last modified 22-01-2008
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