River Torrens water quality improvement trial

The Torrens Lake is an important community asset and tourism icon for Adelaide, but for much of its recent history it has suffered from frequent and repeated blue-green algal blooms. These microscopic blue-green algae are naturally occurring, but can reach high concentrations (or 'bloom') in situations where warm temperatures, stagnant water and high nutrient levels combine.

In high concentrations, blue-green algae can discolour water, form scums, produce unpleasant odours, and release toxins that can be harmful to both humans and wildlife. As a result, once blue-green algae concentrations reach a particular level, the Torrens Lake is temporarily closed to the public for health reasons. Lake closure can extend over weeks or even months, and the social, economic and environmental impact is significant.

What is being done?

The River Torrens water quality improvement project was developed with the support of the Adelaide and Mount Lofty Ranges Natural Resources Management Board, the Department of Environment, Water and Natural Resources, SA Water, the Environment Protection Authority, and Adelaide City Council.

The project has tested a variety of strategies to keep blue-green algal concentrations in the lake down over summer, by providing controlled environmental flows of fresh water that dilute nutrient levels and keep the lake water well mixed.

Environmental flows

Initial trials in 2011-12 and 2012-13 of environmental flows, of around 40 ML/day, proved insufficient to counter high algal growth rates in hot weather. However, since 2013-14 less frequent but higher intensity flows have been used to dilute algal concentrations and ‘reset’ the lake. This approach had a positive outcome, with no lake closures being necessary for the past two summers – 2013-14 and 2014-15.

This summer, environmental flows will again be used in combination with a new trial to test the effectiveness of hydrogen peroxide to control the growth of blue-green algae.

Further information

Water flow data

Water data website 

General information

Restoring fish communities of the lower River Torrens 2011-15

River Torrens water quality improvement trial fact sheets:

The Goyder Institute website 

Background investigations and reports

Feasibility of dilution flows for Cyanobacteria management in the Torrens Lake report Ecological implications for freshwater fishes arising from specific hydrological changes to the lower River Torrens report 
Detention weirs for Torrens Lake for blue green algae reduction report 
Torrens Lake bypass report 
Amenity flow transmission losses; initial investigations report 
Kangaroo Creek reservoir modifications; initial investigations report
Monitoring program to support investigations of dilution flows to control Cyanobacteria in the Torrens Lake report
Torrens Taskforce summary report May 2007


The Goyder Institute, Department of Environment, Water and Natural Resources, SA Water, the Environment Protection Authority and Adelaide City Council


Natural Resources Adelaide and Mount Lofty Ranges