Groundwater quality in Willunga Plains

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Introduction

The Willunga Plains area is 30km south of Adelaide, between the Sellicks Hill Ranges and Gulf St Vincent. Groundwater in the region is used extensively for irrigation of vineyards and orchards in the McLaren Vale-Willunga area as well as for domestic needs. The region is a prescribed wells area (since 1999) to ensure sustainable use of the groundwater systems. >> More

There are four distinct aquifers in the region, with groundwater sourced from three of these. The EPA monitors water quality in all four aquifers. All aquifers are at risk of being contaminated by past and present agricultural sources. Since 1999, reclaimed water from Christies Beach wastewater treatment plant has been used for irrigation to reduce the demands on groundwater.

The main problem with groundwater quality in the Willunga Plains region is elevated nitrogen levels (mainly oxidised nitrogen).

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 eight bores in the Willunga Plains area. The indicators that are measured 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
Oxidised Nitrogen	Moderate	Good	NA	NA
Total Nitrogen	Moderate	NA	Good	NA
Total Phosphorus	Good	NA	Good	NA
Metals	Good	Poor	Poor	Good
Salinity	NA	Poor	NA	Good

Notes NA = Not applicable

For freshwater ecosystems, the groundwater is of moderate quality due to its nitrogen level, which is probably due to inappropriate agricultural practices. The groundwater is classified as poor for drinking water due to high iron and salinity levels. This is largely due to excess irrigation water leaching salts through the soil. For irrigation purposes, the groundwater is poor due to its high iron level. This can lead to problems with irrigation equipment. The groundwater quality in the Willunga Plains is considered good for livestock.

The recent Willunga groundwater quality appears to be consistent with previous results (see graphs below), although this will need to be monitored longer-term to confirm a trend.

Pesticides in groundwater

Groundwater samples are analysed for a number of pesticides that may leach into it 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 affected. Therefore, the detection of any pesticide in groundwater is considered to be a significant problem and warrants further assessment and or management.

The results of groundwater pesticide monitoring in the Willunga Plains

Year	1998	1999	2000	2001	2002	2003	2004	2005
Have pesticides been detected?	No	No	Yes	No	No	NS	NS	No

NS = not sampled

The fungicide Chlorothalonil was detected at one well in May 2000. This fungicide is used on plants and crops and is highly toxic to aquatic organisms. No other pesticides have been detected.

>> Archived results

Download graphs

• Oxidised nitrogen in the Willunga Plains groundwater region
  
• Total nitrogen in the Willunga Plains groundwater region
  
• Total phosphorus in the Willunga Plains groundwater region
  
• Salinity in the Willunga Plains groundwater region
  
• Copper in the Willunga Plains groundwater region
  
• Lead in the Willunga Plains groundwater region
  
• Zinc in the Willunga Plains groundwater region
  
• Iron in the Willunga Plains groundwater region
  
• Soluble aluminium in the Willunga Plains groundwater region
  

Download raw water quality data

• All chemistry data for the Willunga Plains groundwater region
• All pesticide data for the Willunga Plains groundwater region

What is being done to improve groundwater quality in the Willunga Plains

The EPA is responding to problems with groundwater in the Willunga Plains by requiring licensees who could pollute groundwater to monitor water quality. For example, see the Guidelines for Wineries and Distilleries (563KB PDF).

The Adelaide & Mount Lofty Ranges NRM Board has produced a Draft Water Allocation Plan for the McLaren Vale Prescribed Wells Area following a review of the existing plan to ensure the sustainable use of the groundwater systems.

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 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 23-09-2008