Photo: Australian
Water Quality Centre |
Introduction
The Wakefield River is a brackish to saline stream in the Mid
North of the state. This site at the Rocks is in the lower reaches
of the catchment near the town of Balaklava.
The Wakefield River is an ephemeral system, characterised by
irregular flows and long dry intermediate periods. The typically
low soil moisture levels mean that most rainfall is absorbed into
the landscape or riverbed. When flows do occur, they do so as
a pulse of water rather than a slow incremental flow (source:
River
Management Plan for the Wakefield Catchment).
Land use in the Wakefield catchment is a mixture of broad acre
grazing, cropping and vineyards. Elevated turbidity and nutrient
levels are the most likely water quality problems. The site is
surrounded by native vegetation. Stream
flow for this site is available from the Department
of Water, Land and Biodiversity Conservation. >>
Map (689KB PDF)
Water quality assessment
Water quality is assessed as being in good, moderate or poor
condition by interpreting ecological health and water chemistry
data in the context of protecting environmental values. >>
More
Ecological health is assessed in spring and autumn. We use macroinvertebrates
for this purpose because they provide a relatively simple way
to assess the health of an aquatic ecosystem. >>
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Water chemistry is measured each month. We measure chemical indicators
because when they reach a certain level they can cause stress
or toxicity to animals and plants in an ecosystem. Some indicators
can also indicate if the water is suitable for drinking water
or for activities such as swimming. >>
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Ecological health
We collect two samples of macroinvertebrates, one from riffle
(or flowing water) habitat and one from edge (still water) habitat.
The diversity of the macroinvertebrate community is used to describe
ecological health as being in good,
moderate or poor
condition.
Go
here to find out how we classify ecological health in streams.
Ecological health assessment for June 2006
| Habitat |
Ecological health
|
| Edge |
Moderate
|
| Riffle |
Poor
|
The Wakefield River at the Rocks has generally changed from a
good condition in 2003 to a slightly impaired stream from 2004
onwards. The results from autumn 2006 indicate that the stream
continues to remain in an impacted state, although there is insufficient
data at this stage to explain why this has occurred.
The edge habitat had only 17 different types of macroinvertebrates
present and the most common species were hydrobiid snails and
oribatid mites. The riffle habitat had 19 types of macroinvertebrates
with large numbers of oribatids, non-biting midges (Cricotopus
species) and blackfly larvae (Simulium ornatipes).
The riffle habitat at this site rated poorly due to the absence
of ceinid amphipods, freshwater shrimps, odonates, mayflies and
caddisflies. However, the site habitat is able to support a more
diverse ecosystem and the concentrations of most water quality
indicators are normal for this mid- north stream, so it is possible
the brackish (about 4,000 mg/L) salinity or presence of large
numbers of introduced mosquito-fish have reduced the number of
macroinvertebrates able to survive and thrive at this site.
Download ecological health data
Water chemistry
The indicators that are measured in the Wakefield River are nutrients
(nitrogen and phosphorus), turbidity and salinity.
The concentrations of these indicators are used to classify the
water chemistry as being in good,
moderate or poor
condition, according to the needs of aquatic ecosystem protection.
Go here
to find out how we organise and classify the chemistry data.
Water chemistry classification for April to September 2006
|
Indicator
|
Classification
|
|
|
Good
|
|
|
Good
|
|
|
Good
|
|
|
Good
|
|
|
Good
|
The nutrient and turbidity levels were low in the Wakefield River
for this period. Occasionally, during high flows, turbidity, total
nitrogen and total phosphorus can be elevated at this site, although
the soluble nutrients have been consistently at low concentrations.
The Northern
& Yorke NRM Board is developing an NRM Plan for this region.
The River
Management Plan for the Wakefield Catchment (2000) identifies
priorities for the lower reaches of the Wakefield River, including
the maintenance of native plants and removal of artichoke weeds.
>> Archived results
Download water chemistry graphs
Download raw chemistry data
What is being done to improve the condition
of South Australian rivers and streams
Efforts to improve the condition of South Australia's rivers
and streams are being driven by various government agencies, primarily
The Environment Protection Authority
The Department
of Water, Land and Biodiversity Conservation
Natural
Resource Management Boards
Department
for Environment and Heritage (SA)
Collaborative projects and programs being run by these agencies
are based on the protection of environmental values, as explained
in the National
Water Quality Management Strategy. >>
More
This page was last modified 25-09-2007
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