Lake Bonney is a large coastal lake about 10 km south of Millicent in the South East of South Australia. Like most of the region, it has been extensively altered since European settlement, particularly by the effects of drainage schemes and various agricultural land use impacts.
Why are we interested in Lake Bonney?
Lake Bonney has been damaged by the discharge of large amounts of nutrients and contaminants from pulp and paper mills for over 70 years, and smaller volumes have also entered the lake from the Millicent wastewater treatment plant for over 45 years. This has prompted a range of responses from both the industries involved and government, particularly over the past two decades, to try and improve the quality and reduce the volume of wastewater that is discharged to the lake. These actions were carried out with the aim of improving the environmental condition of the lake. The recent closure of the Tantanoola Mill in 2012, for example, has significantly reduced the amount of coloured substances and nutrients discharged into the English Gap Drain and ultimately into the eastern side of Lake Bonney.
The lake is no longer the foaming, red coloured waterbody that it was in the 1980s, when it was locally considered too polluted for the public to visit. Over the past few years, the lake has become much clearer and today most of its yellow-brown colour is caused by large blooms of small algae called phytoplankton.
The lake is still brackish, alkaline, well oxygenated and it remains highly enriched with nutrients such as nitrogen and phosphorus. It is in the biology of the lake, however, where major improvements to the plants and animals inhabiting the lake have been noted over the period from about 2005 to the present. Several types of native fish breed in the lake, some in large numbers, and include threatened species such as Southern Pygmy Perch and Dwarf Galaxias that typically occur in well-vegetated habitats around the edges of the lake. Aquatic plants grow a few hundred metres into the lake and include a wide range of submerged and fringing species.
Large numbers of waterbirds regularly use the lake as a feeding and breeding site, tortoises and yabbies are often recorded in low numbers throughout the lake, and an increasingly diverse range of aquatic macroinvertebrates (eg waterbugs, beetles and crabs) inhabit the lake compared with what was recorded during the 1970s to 1990s.
Despite these improvements, the nutrients in the lake remain too high and they pose an ongoing risk that a significant bloom of blue-green algae (or cyanobacteria) could form and result in major losses of many of the fish, plants and invertebrates that occur in Lake Bonney. Consequently, future management will be directed towards trying to reduce the addition of new nutrients from the paper mill, wastewater treatment plant and also from cattle and sheep that graze along many of the drains in the lake's catchment and along the northern shoreline.
What has already been done to improve water quality in Lake Bonney?
In November 1996 the Lake Bonney Management Committee published the Lake Bonney Management Plan 1996–2000 to provide guidelines for the future management of the lake, which will allow the continued recovery of the lake, protection of the natural values and the establishment of an amenity for use by the wider community’.
In 2003 the EPA, Office of Economic Development and Kimberly–Clark Australia funded a three-year project to assess the condition of Lake Bonney and identify actions that could be taken to improve the health of the lake. Between 2004 and 2006, the results were discussed with representatives of the local community and interest groups and the consistent view expressed after completion of this project was that the Lake should be restored to a healthy ecosystem mainly through avoiding or significantly reducing the inflow of nutrients from all sources in the future.
The study, which concluded in 2007, identified the high nutrient load from the mills presented a high risk for the ecology of Lake Bonney as the receiving environment for the wastewater. Negotiations are underway in terms of the licences that will be required for the mills in 2014.
In recent years Kimberly–Clark Australia have made the following changes in how they operate which has improved water quality in the lake:
- ceased using bleaching process in paper manufacturing
- reduced water use resulting in smaller volumes of wastewater
- closed the pulp mill which significantly improved water quality.
Reports now show that the water quality of the lake has improved, and this provides the ideal time to discuss setting a future vision for everyone with an interest in Lake Bonney to help achieve the desired community agreed environmental values over the next few decades.
The EPA has been working closely with Kimberly–Clark Australia to identify options to avoid or minimise the release of wastewater into the lake’s catchment and undertaken a range of further monitoring studies of the lake.
Setting environmental values
The EPA considers that the condition of the lake has improved sufficiently in recent years to seek the community's views about the sorts of environmental values that the lake should be able to support in the future. Community consultation occurred during 2012 via public meetings, targeted meetings with a range of interest groups, and an invitation to provide feedback using a web-based feedback sheet. A consultation report was released in March 2013 that summarises the environmental values identified by the community. The EPA is currently developing water quality guidelines and reviewing the existing monitoring and assessment of the lake. We expect to get back to the community towards the end of 2013.
- LakeBonney, South East, South Australia – Past, Present and Possible Future
- Dioxins and dioxin-like organic contaminants (dioxins, furans and polychlorinated biphenyls) in Lake Bonney, South East
- LakeBonney Management Plan 1996–2000
- Establishing environmental values and water quality objectives
- Report of the consultation and the community's aspirational environmental values, March 2013