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4 Αυγούστου 2010

Olympic legacy and clean water

Aπο το περιοδικό: World Rowing Magazine
Located in Penrith, north of Sydney, SIRC is built on a former sand and gravel quarry. The
developers of Penrith Lakes had to work within the quarry environment and create a suitable
ecosystem to achieve the goals of making a public sport and recreation space. The ongoing
goal is to ensure that the water quality in the main lakes reaches the “primary contact water”
standards at least 95 per cent of the time, which is the acceptable level for people to swim in.
As the water supply for the regatta lakes comes from urban runoff and storm water which is
potentially turbid and high in pathogens, four detention basins (treatment areas) were built.
These basins act to purify the water before it is released into the regatta lakes. This purification
is achieved through the use of native aquatic plants chosen for their ability to absorb nitrates
and phosphates while the clay sediment in the basins acts to absorb metals.

The purifi ed water can then go into the regatta lakes where 25,000 aquatic plants have been planted
along with the introduction of 65,000 Australian bass (fi sh) as part of the creation of a working ecosystem. “We only use species indigenous to the area,” says Kevin Flynn, SIRC venue manager.
As the water in the lake is static, two underwater aeration fans have been built as well as an aeration line that runs the full length of the warm-up and competition lake. These fans are used to help plant growth and prevent stratification of the water. But despite these measures some challenges in water quality, like algal bloom, still occur.
Algal bloom, which can cause the water to become toxic, inhibits the use of the lakes for sports which require contact with the water, like swimming. The bloom can be caused by stratification, where water temperature differs through the layers. In February this year algal bloom occurred, says Flynn, after a particularly high rainfall. Watersports had to be cancelled until the bacteria concentrations fell to acceptable levels for primary contact water.
The high rainfall also meant that untreated water went directly into the regatta lakesSIRC works with Penrith Lakes Development Corporation (PLDC), in water management. Matthew Zollinger is the manager for Land and Water at Penrith Lakes. “We are trying to shift our water quality basins into more of a macrophyte
(aquatic plant) dominated system instead of an algae dominated system which will help to reduce the occurrence of algae blooms. We are looking at plants that can tolerate a large variance in water levels and are investigating using a floating raft system.” Zollinger says reactive algae treatment is also being considered
like algal herbicides. Zollinger adds that there is currently work to increase storage capacity upstream to reduce the occurrences when water has to be released directly into the regatta lakes. An ongoing study of freshwater mussels is being monitored as these indigenous mussels have the ability to filter water. Flynn says so far there have been some good results.” They play a significant role in filtering water, removing phytoplankton, fine organic matter, bacteria and metal ions,” says Flynn. “The filtration rate is believed to be
in the order of 20 mussels filtering 20 litres of water in 24 hours.”
Keeping the water clean is an ongoing exercise and is key to the success of the site. SIRC receives
around 50,000 visitors per month and hosts trials for the Australian National Rowing Team and various regattas. So far the success has been high.

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