River Torrens water quality
improvement project
SUMMER 2014-15
The City of Adelaide has grown up around the banks of the River Torrens and its tributaries. A significant part
of the catchment is highly urbanised, particularly from the foothills across the Adelaide plains.
What’s the problem?
Water quality in the urban sections of the River Torrens
is often poor due to stormwater runoff from the builtup urban environment and the lack of flows from
upstream.
Over summer, water quality management in Torrens
Lake becomes a particular challenge.
Hot and dry weather conditions mean that water
They are also potentially toxic containing neurotoxins,
liver toxins and skin allergens – and in very high
concentrations, can lead to the death of domestic
animals and fish.
For public health reasons, when there are blooms, the
lake is closed to users.
Fresh water flows to prevent bluegreen algal blooms
temperatures increase, creating the perfect conditions
Fresh water flows from upstream reservoirs will be
for blue green algal growth.
released into the River Torrens over summer to dilute
If blue green algae takes hold in Torrens Lake, it can
result in temporary closures of the lake for public health
blue green algae levels, reducing the likelihood of a
bloom.
reasons, impacting on recreational activities.
The flows control algal growth by adding fresh water to
What is blue-green algae?
the system, keeping the normally sedentary water
Blue green algae is a naturally-occurring organism that
diluting the naturally-occurring blue green algal
can be found in almost every terrestrial and aquatic
concentrations.
habitat, from oceans to fresh water, bare rock to soil.
moving and mixing, lowering water temperatures and
This summer, the dilution flows will come from
In moderate quantities it is quite harmless. However,
Kangaroo Creek Reservoir with each flow extending
under certain conditions, such as high water
over a 3-4 day period.
temperatures and in sedentary bodies of water, some
types can begin to dominate causing algae blooms or
outbreaks.
These blooms are unsightly and emit an unpleasant
odour.
Regular monitoring of blue green algae levels will be
used to determine when the flow is most needed.
This action mirrors the effective approach taken last
summer when the SA community was able to enjoy the
lake fully with no closures necessary.
Trial of hydrogen peroxide
A field trial is also planned for this summer to safely
investigate the use of hydrogen peroxide as a potential
algaecide.
If this trial is successful, hydrogen peroxide may be an
option for future use as a way to combat blue green
algal blooms.
The trial will build on laboratory work by the CSIRO
using hydrogen peroxide in a stabilised granular form
to control blue green algae.
Initially the hydrogen peroxide treatment will be trialled
in small, temporary pools set up on land adjacent to the
River Torrens.
The pools will be filled with water and algae from the
50 recommendations, many of which have been
implemented.
Monitoring the results of the flows
Regular monitoring of the water in Torrens Lake and in
the river, upstream and downstream, will continue.
The monitoring will enable good decision-making
around the timing of fresh water flows during the trial.
The monitoring will also enable us to keep an eye on
water quality at the outlet and to inform beach users of
any risks through the EPA beach alert website.
Is this a good use of water?
The Torrens Lake is an important community asset and
tourism icon for Adelaide.
lake and varying doses of hydrogen peroxide used to
It is important that we continue to manage the health of
test the levels needed to control blue green algae in the
the system in the best possible ways to make sure the
open environment.
lake is usable and safe each summer, and that the river
If initial testing shows the use of hydrogen peroxide is
beneficial, it will be tested in a localised area of Torrens
Lake.
What else is done to care for the River
Torrens and lake?
A variety of state and local government agencies work
together to care for the River Torrens.
Finding effective solutions to the year-round challenges
faced by the entire Torrens system is ongoing.
In 2006, the Torrens Taskforce was set up to investigate
strategies to manage the River Torrens’ water quality.
The taskforce consisted of water managers, scientists
and engineers, and in 2007 identified more than
is healthy.
Any downstream impacts of the fresh
water flows?
When the high intensity flows are released, residents
and visitors to the River Torrens Linear Park may notice
higher than usual flows in the river for up to five days at
a time as water makes its way from the hills, through
the city to the Torrens outlet at West Beach.
Local residents and visitors may also notice the water as
it exits the river system to the sea.
The water will be better quality than stormwater.
However, at any time, people are encouraged to avoid
swimming in turbid or discoloured water.
More information
You can monitor water data at the Natural Resources Adelaide and Mt Lofty Ranges website.
Visit: www.naturalresources.sa.gov.au/adelaidemtloftyranges
The fresh water flows and hydrogen peroxide trials are being led by the Adelaide and Mount Lofty Ranges
Natural Resources Management Board, Department of Environment, Water and Natural Resources, the City of
Adelaide in collaboration with the Environment Protection Authority and SA Water