Introduction
Groundwater in the state's South East is an important source
of water for agriculture and industry and is the major source
of the regions drinking water. >>
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There are two aquifers throughout most of the South East - an
upper unconfined aquifer and a lower confined aquifer. The EPA
mostly monitors water quality in the unconfined aquifer. This
aquifer is most widely used and is at most risk of being affected
by pollution from past and present agricultural and industrial
sources because the water table can be within 5 meters of the
surface.
Groundwater contamination of the unconfined aquifer is the result
of either point source contamination (e.g. spills from copper-chrome-arsenate
wood preservation industries) or diffuse source contamination.
Point source contamination of the aquifer has occurred due to
the historic disposal of wastes into the unconfined aquifer from
industries such as dairies, timber mills, gasworks, cheese factories,
abattoirs and septic disposal.
Inappropriate pesticide use has resulted in ground-water contamination,
to the extent that organochlorine and triazine pesticides have
been detected in ground water in parts of the region, including
as part of the EPA ambient program.
Diffuse source contamination of the unconfined aquifer has occurred
due to agricultural activity and forestry. Diffuse nitrate pollution
has had the largest effect on the aquifer with increasing nitrate
levels being observed in the groundwater in the Blue
Lake Capture Zone and the Coonawarra
area. Pesticides have also
been detected in the lower South East. The issue of diffuse source
contamination is being addressed by better land management practices.
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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This assessment represents groundwater across the whole of the
South East. Water quality assessments can also be found for specific
regions, including Coonawarra, Padthaway,
Millicent, Keith
and the Blue Lake Capture Zone.
Groundwater samples are collected annually from 70 bores across
the South East region. The indicators that are measured in the
unconfined aquifer in the South East are nutrients (nitrogen and
phosphorus), heavy metals, arsenic 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
|
|
|
NA
|
Poor
|
NA
|
NA
|
|
|
NA
|
Good
|
NA
|
NA
|
|
|
Poor
|
NA
|
NA
|
NA
|
|
|
Poor
|
NA
|
Good
|
NA
|
|
|
Good
|
NA
|
Moderate
|
NA
|
|
|
Good
|
Moderate
|
Moderate
|
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.
Note also that, although some of the groundwater in the South
East does flow into Blue Lake (Mt Gambier), which is an important
drinking water supply, the nitrate and nitrite concentrations
in Blue Lake itself are at safe levels for drinking water quality,
including young infants.
Elevated salinity in groundwater across the South East also means
that drinking water quality is poor. 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 moderate because of elevated
metal concentrations, although this is mostly due to iron, which
discolours water.
Metals are considered moderate for irrigation purposes due to
elevated iron which can clog irrigation pipes. Total phosphorus
is considered moderate for irrigation because it may lead to clogging
irrigation pipes through biological fouling.
Pesticides in groundwater
Groundwater samples are collected annually from 47 bores 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. >>
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If pesticides are detected in an aquifer, the environmental values
of the aquifer are compromised. Therefore, the detection of any
pesticides in groundwater is significant and warrants further
assessment and or management response.
The results of groundwater pesticide monitoring in the South
East
|
Year
|
1998
|
1999
|
2000
|
2001
|
2002
|
2003
|
2004
|
2005
|
|
Have pesticides been detected?
|
Yes
|
Yes
|
Yes
|
Yes
|
Yes
|
NS
|
Yes
|
No
|
NS = Not sampled
No pesticides were detected in any of the South East groundwater
monitoring bores during 2005. In previous years, pesticides were
found, although several of these were for a single pesticide detected
at the same bore over several years indicating possible localised
misuse. Pesticide sampling will continue to see whether this trend
continues.
>> Archived results
Download graphs
Download raw water quality data
What is being done to improve groundwater
quality in the South East
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 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.
This page was last modified 24-07-2007
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