The first large-scale deployment of a floating wetland in the ACT is a key component of works to improve the water quality in Lake Tuggeranong.
Monitoring of the gross pollutant trap (GPT) in Village Creek just downstream of Athlon Drive has shown that in between storms the GTP releases more nutrients than enter it! In the summer heat, leaves, grass and other organic matter 'stew' in the gross pollutant trap, releasing nutrients that pollute the embayment just below it. This embayment leads directly to Lake Tuggeranong. The government is concerned that blue-green algal blooms might begin in the warm, nutrient-rich waters of the embayment and then spread to the lake.
The GPT is being modified to better drain following storms, and low-flows will now bypass the trap and flow directly to the embayment so that the trap is not constantly wetted.
The floating wetland covers an area of 500m2 and is made of recycled plastic bottles and styrene, and covered with coir mat. It is non-toxic to fish and other biota.
Local native water plants have been placed in special wells in the wetland platform. Over the next year they will expand across the platform and extend their roots down into the underlying water column. The floating wetland will then compete with algae for nutrients and light, to stop the embayment from 'seeding' algal blooms that spread to the lake.
The floating wetland has been deployed away from the water's edge for public safety. There are nets covering the platform to prevent birds from uprooting the plants while they are young. The nets will be removed once the plants are well established.
The floating wetland is a two-year trial during which the performance and maintenance costs of the wetland will be monitored. If the floating wetland is found to be effective it will be maintained within the embayment. Otherwise it will be redeployed in a stormwater pond elsewhere in the ACT.
