Overview of groundwater quality in the South East

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Archived water quality assessments

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

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
Nitrate	NA	Poor	NA	NA
Nitrite	NA	Good	NA	NA
Oxidised Nitrogen	Poor	NA	NA	NA
Total Nitrogen	Poor	NA	Good	NA
Total Phosphorus	Good	NA	Moderate	NA
Metals	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. >> More

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.

This page was last modified 24-07-2007