Before urbanisation
Before an area is urbanised, rain would have infiltrated the
soil and recharged groundwater or slowly runoff into streams and
coastal environments. Water quality would only be influenced by
natural processes. >> More
How does urbanisation change things?
Urban areas have large areas of hard surfaces such as concrete,
bitumen and roofs, which don't allow rain to percolate into the
soil. Instead, rainwater runs off these hard surfaces very quickly,
becoming what is called stormwater.
As stormwater travels across roads, carparks, gardens, etc, it
collects many pollutants that are produced in cities. These pollutants
include litter (e.g. plastic bags and drink bottles), nutrients
(e.g. phosphate and nitrate in fertilisers and detergents), heavy
metals (e.g. copper from motor cars and zinc from metal roofs),
suspended solids (e.g. through soil erosion on building sites)
and disease-causing bacteria (often from overflowing sewage pipes).
How does urbanisation affect water quality?
As urbanisation has reduced water infiltration and groundwater
recharge, urban streams now don't flow for long periods. Now,
during rain events, urban areas quickly generate stormwater, inducing
fast stream flows of short duration. This urban stormwater carries
many pollutants that are quickly transported to downstream water
bodies such as the creeks which run through an urban area (e.g.
Dry Creek and Sturt Creek). They
then flow to the coastal environments of metropolitan Adelaide.
The effects of these polluted stormwater discharges can include
significant ecological changes to the plant and animal communities
in both urban streams and coastal waters, as well as rendering
water unsafe for recreational activities.
What is being done to reduce the impacts
of urbanisation?
The EPA is coordinating the Adelaide Coastal
Waters Study which is partly in response to the problems that
urban stormwater has created in our metropolitan coastal environment.
The EPA has also released codes of practice for stormwater pollution
prevention. >> More
The EPA is using stormwater modelling to assist with determining
how much pollution is due to urbanisation. Pollutant loads are
estimations of the amount of pollutant transported by a stream
over time (units in mass/time e.g. kg/yr). >> More
Water quality monitoring
There are several sites around the Adelaide metropolitan area
that the EPA monitors because they are likely to be affected by
urban stormwater. These are:
Streams
Beaches
Port Waterways
Patawalonga Lake
The Natural
Resources Management Boards also operate monitoring programs
through the metropolitan area to assess the water quality throughout
the catchments.
This page was last modified 05-12-2006
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