Controlling blue-green algae in the lake has been most successful when releasing flows down the river – high flow rates, for a short duration, mix up and cool down the water – as well as benefiting the whole river system. Highbury Windsor Gardens Lochiel Park Catchment Monitoring Infrastructure Vale Park Felixstow management • Every 15 minutes, temperature, dissolved REMOVING LARGE ITEMS OF RUBBISH St Peters Flinders Park Adelaide oxygen and salinity, and weather conditions Adelaide • Gross pollutant traps on all stormwater Lockleys Hills • Removed over 3.5 tonnes Adelaide are measured from 3 permanent water of Carp directly entering the lake quality monitoring stations in the lake • Gross pollutant traps throughout • Erosion prevention and Gulf St • Twice weekly water quality monitoring the catchment, including on First, Vincent riverbank planting at 7 locations over summer Second, Third, Fourth and Fifth creeks • Woody weed removal + capturing over 5000 tonnes in the last • Weekly water quality monitoring along replanting with native two years the river – including the sea at the outlet plants along linear park • Floating boom on the river in St Peters • Twice yearly fish monitoring along the • Over 15,000 native aquatic river and around the lake MINIMISING NUTRIENTS IN THE LAKE plants placed in the lake • Duck feeding station in the lake closed • Regular dredging of the lake, • Aquatic plants added to take up nutrients 3 with over 3000m removed • Floating wetlands (aquatic plants grown on a floating platform) in 2017 being trialled near Torrens Weir • Fencing-off stock from • Phoslock (a chemical that gets rid of phosphorus) trialled in 2006 rural areas Hydrogen peroxide trials STORMWATER HARVESTING AND REUSE • Major clean up after 2016 • First Creek wetland and stormwater reuse scheme created storms deposited litter, • Hydrogen peroxide was trialled as it was organic matter and sediment known to kill blue-green algae, but not • Linde Reserve biofilter and stormwater reuse scheme created affect other aquatic species • Felixstow Reserve wetland and stormwater reuse scheme created • 2017 and 2018: trials near the zoo • 2016: trial near the weir IMPROVING WATER QUALITY • Aerators, to add oxygen to the water, trialled • 2014 and 2015: trials in the laboratory and in small ponds • 2008 and 2012 trials of transportable biofilter to clean up the water • Flows trialled at different flowrates from 3–5 days, mix up, cool and exchange the water These Torrens Lake activities were developed with the support of the Green Adelaide Board, the Department for Environment and Water, City of Adelaide, the Environment Protection Authority and SA Water. Managing Adelaide’s central jewel over a hot, dry summer Torrens Lake update: summer 2020–21 The River Torrens and Torrens Lake form one of Adelaide’s most recognisable landscape features. Together they make important social, economic and environmental contributions to the city and the wider metropolitan area. Each year over summer, water stops flowing into If needed, flows will again be released over the lake and so it heats up, becoming susceptible summer, timed to counter rising algae levels to blue-green algae blooms. and minimise beach impacts. Over the past decade, a wide range of initiatives Most flows start on a Friday afternoon from have been trialled in the lake and the broader the reservoir, potentially reaching the beach River Torrens catchment to reduce the frequency at Henley South late Sunday evening. and intensity of these blooms, which can discolour water, form scum, and produce unpleasant odours. The flows continue for up to five days, and the At a high intensity they can also release toxins outlet channel is excavated at the beach before that can harm humans and wildlife. each flow to ensure the water heads directly to the sea. These trials have shown that there is no single solution to reducing blue-green algae growth Regular monitoring has shown that the sea is safe over summer, and that any long-term, sustainable to swim in, although advice remains to not swim plan will involve many options and the collaboration in discoloured water. of many stakeholders. As well as maintaining an open lake over the So far, regular flows of fresh water into Torrens coming summer, work continues to explore Lake have been most successful at controlling complementary, long-term, sustainable options. blue-green algae growth, and keeping the lake open since February 2013. High flows released from Kangaroo Creek reservoir mix up and cool down the water in the lake, successfully disrupting the growth of algae. How much water is released depends on summer weather conditions at the time, such as how hot it is, and the frequency and volume of recent rainfall..