Introduction
The Northern Adelaide Plains area is situated 10 to 40 km north
of Adelaide, and covers about 750km² of the Adelaide coastal
plains. Groundwater in the region is used extensively for irrigation
of crops such as vegetables, fruits, flowers and nursery plants
as well as for industrial processes in the southern section of
the region. >> More
There is a complex mixture of confined and unconfined aquifers
in the region, with the groundwater sourced mainly from two relatively
deep confined Tertiary aquifers. The EPA monitors water quality
in these two aquifers throughout the region. As the aquifers are
confined, the risk of being affected by contamination is restricted
to pollutants introduced down wells and leakage down old 'leaky
wells' that exist throughout the region.
Reclaimed water from the Bolivar wastewater treatment plant is
pumped to Virginia through an irrigation scheme to be used by
market gardeners to reduce the demands on the groundwater system.
The main issues regarding the groundwater quality in the Northern
Adelaide Plains are the high nitrogen levels (mainly as nitrate)
and the high salinity.
Water quality assessment
Water quality is assessed as being in good,
moderate or poor
condition by interpreting water chemistry data in the context
of protecting various environmental values. >>
More
Groundwater samples are collected annually from 8 bores in the
Northern Adelaide Plains area. The indicators that are measured
in the aquifer systems in the Willunga Plains area are nutrients
(nitrogen and phosphorus), heavy metals and salinity. The environmental
values that need to be protected are freshwater ecosystems, drinking
water, irrigation use and livestock use.
Water quality classification for 2005
|
Indicator
|
Ecosystem
|
Drinking Water
|
Irrigation
|
Livestock
|
|
|
Good
|
Good
|
NA
|
NA
|
|
|
Good
|
NA
|
Good
|
NA
|
|
|
Good
|
NA
|
Good
|
NA
|
|
|
Good
|
Poor
|
Poor
|
Good
|
| Salinity |
NA
|
Moderate
|
NA
|
Good
|
Notes NA = Not applicable
The groundwater is classified as moderate for drinking water
quality due to elevated salinity. Some of the elevated salinity
is likely to be due to natural variations. However, salinity increases
are largely due leakage of saline water from shallow aquifers
and seepage from underlying saline aquifers due to pressure reductions
in the aquifer. The salinity was between 550mg/L and 2000 mg/L,
while the NH&MRC
guideline (for taste) has a low value of 500mg/L and an upper
value of 1000mg/L. >>
More
The poor metals for drinking water is due to iron levels being
greater than the NH&MRC
guideline for taste and appearance of 0.3mg/L.
There are almost 3000 abandoned groundwater wells in the Northern
Adelaide Plains. It is possible that many of these have become
'leaky'. A leaky well can allow water from the upper unconfined
Quaternary aquifer to seep down into the confined Tertiary aquifer
through corrosion of the well casing. There is the potential that
these leaky wells are contributing to a decline in water quality
of the lower Tertiary aquifers.
Overall, the groundwater quality in the Northern Adelaide Plains
area is considered good for irrigation and livestock with the
exception of elevated iron levels that can clog irrigation pipes.
Pesticides in groundwater
Groundwater samples are collected annually and analysed for a
variety of pesticides that may be leached to the unconfined aquifer
as a result of past or present agricultural practices. Pesticides
analysed in groundwater samples include several herbicides, fungicides
and insecticides. >> More
If pesticides are detected in an aquifer system, the environmental
values of the aquifer are potentially impacted. Therefore, the
detection of any pesticides in groundwater is considered significant
and warrants further assessment and or management response.
The results of groundwater pesticide monitoring in the Northern
Adelaide Plains area
|
Year
|
1996
|
1997
|
1998
|
1999
|
2000
|
2001
|
2002
|
2003
|
2004
|
2005
|
|
Have pesticides been detected?
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
No
|
Download graphs
Download raw water quality data
What is happening to improve groundwater
quality
Several projects have been designed to reduce the impacts on
the groundwater in the Northern Adelaide Plains aquifers. The
Department of Water, Land and Biodiversity Conservation has
completed the Leaky
Wells Project that backfilled old unused and poorly constructed
wells so that they are no longer a direct source of pollution
to the aquifer. The use of reclaimed water from the Bolivar wastewater
treatment plant through the Virginia irrigation scheme is expected
to increase in the future and this will reduce the demands on
the aquifer. Also the expansion of Aquifer storage and recovery
(ASR) where treated stormwater is injected into the aquifer may
reduce the demands on the aquifer.
In a more general sense, the EPA works with the Adelaide &
Mount Lofty Ranges Natural Resource Management Board, the community
and industry to increase awareness of groundwater quality problems
and develop appropriate management strategies. >>
More
Efforts to improve the condition of South Australia's groundwater
resources are being driven by various government agencies, primarily
The Environment
Protection Authority
The Department
of Water, Land and Biodiversity Conservation
Adelaide
and Mt Lofty Ranges Natural Resources Management Board
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.
This page was last modified 24-07-2007
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