Introduction
Groundwater in the Millicent area in the state's South East is
part of the aquifer system that is present throughout the South
East. This groundwater is an important source of water for industry
and agriculture. >>
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There are two aquifers in the area - an upper unconfined aquifer
and a lower confined aquifer. The EPA focuses its water quality
monitoring on the unconfined aquifer in the area. This aquifer
is at most risk of being affected by pollution from past and present
agricultural and industrial sources because the water table is
within 5 metres of the surface.
The main issues with the groundwater near Millicent are the high
nitrogen levels (mainly as nitrate).
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. >>
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Groundwater samples are collected annually from seven bores in
the Millicent area. The indicators that are measured are nutrients
(nitrogen and phosphorus), heavy metals, arsenic and salinity.
The environmental values that need to be protected are freshwater
ecosystems, irrigation use and livestock use. The following water
quality classification is based on the most recent data.
Water quality classification for April to September 2005
|
Indicator
|
Ecosystem
|
Drinking Water
|
Irrigation
|
Livestock
|
|
|
NA
|
Poor
|
NA
|
NA
|
|
|
NA
|
Good
|
NA
|
NA
|
|
|
Poor
|
NA
|
NA
|
NA
|
|
|
Poor
|
NA
|
Good
|
NA
|
|
|
Good
|
NA
|
Moderate
|
NA
|
|
|
Good
|
Poor
|
Poor
|
Good
|
| Salinity |
NA
|
Poor
|
NA
|
Good
|
NA = not applicable
Overall, the groundwater quality in the South East is considered
poor for freshwater ecosystems due to the high nitrogen concentration,
which is most likely due to inappropriate agricultural practices.
In terms of drinking water quality, the groundwater in the South
East is poor because of elevated nitrate. Nitrate can cause methaemoglobinaemia
(Blue Baby Syndrome) in young infants. The South
Australian Department of Health recommends that groundwater
users in the South East should have bore water tested for nitrate
if they intend to use it as drinking water. The Australian
Drinking Water Guidelines recommend a guideline value of 50
mg-nitrate/L to protect bottle-fed infants under 3 months of age.
Up to 100 mg-nitrate/L can be safely consumed by adults and children
over 3 months of age.
Elevated salinity in groundwater across the South East means
that drinking water quality is poor because of its effect on taste.
That is, salinity generally exceeds the recommended level of 500
mg/L as a taste guideline (see the Australian
Drinking Water Guidelines). The high salinity is largely due
to excess irrigation water leaching salts through the soil. Drinking
water quality is also considered poor because of elevated metal
concentrations. This is mostly due to iron, which can discolour
water.
Metals are considered poor for irrigation purposes due to elevated
iron which can clog irrigation pipes. Total phosphorus is considered
poor for irrigation because it may lead to clogging irrigation
pipes through biological fouling.
Pesticides in groundwater
Groundwater samples are collected annually and analysed for a
variety of pesticides that may be leached into the unconfined
aquifer as a result of past or present agricultural practices.
Pesticides analysed in groundwater samples include several herbicides,
fungicides and insecticides. >>
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If pesticides are detected in an aquifer system, the environmental
values of the aquifer are reduced. 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 Millicent
area
|
Year
|
1998
|
1999
|
2000
|
2001
|
2002
|
2003
|
2004
|
2005
|
|
Have pesticides been detected?
|
No
|
No
|
No
|
No
|
No
|
NS
|
No
|
No
|
NS = Not sampled
>> Archived results
Download graphs
Download raw water quality data
What is being done to improve groundwater
quality
The EPA is responding to the groundwater issues in the South
East in several ways. The EPA operates a regional office in Mt
Gambier. One of the roles of this office is to manage and regulate
potential pollution of the groundwater. Along with monitoring
programs targeting regional groundwater and Blue Lake, other work
includes:
- groundwater monitoring programs for licensees with potential
to pollute groundwater
- a risk assessment of groundwater contamination due to historical
and current copper-chrome-arsenate timber treatment plants
- a risk assessment of pollution threats to Blue Lake as a joint
Government and CSIRO research project
- development of a Code of practice for regional stormwater
disposal
The EPA works with regional management boards, community and
industry to increase awareness of groundwater quality problems
and develop management strategies. There are close links between
groundwater quantity, quality and supply in the South East. The
EPA is also working with the Department
of Water, Land and Biodiversity Conservation to understand
the flow patterns around and into the Blue Lake. This work will
feed into a risk assessment of the lake. >>
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This page was last modified 24-07-2007
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