Bio-retention basin
Description
Systems such as the wetland, rainwater tanks, wicking beds and bio-retention basin are used to show home gardeners, planners and developers how to protect natural waterways using plants and how to re-use or reduce water usage. Plants reduce flood risk and soil erosion and can help to remove contaminants including heavy metals, sediments and high nutrients (nitrogen, phosphorus, etc.).
Water sensitive design principles can improve habitat quality and add landscape and aesthetic value. Base plants must evenly filter water flow without blocking it and should form dense root mats that stabilise the bed, so a channel does not form. Additionally, the plants must tolerate long periods of waterlogging and extended dry periods over summer.
Background
The wholesale nursery uses sprinklers for irrigation. Until 2020, excess water pooled in parts of the nursery, causing algae to grow, attracting bees in summer and causing a slip hazard for staff and volunteers. Through grant funding as part of the Australian Government’s Future Drought Fund, the Wholesale Nursery drainage was upgraded.
As part of the grant funding, a bio-retention basin and retention tank were constructed at the lower end of the nursery to capture and enable recycling of all run-offs in 2021. During peak flows the retention tank fills up and allows the bio-retention basin to retain water.
A swale directs any excess water from the nursery to the basin. In 2023/24, local sedges and rushes were planted in the swale and low-lying parts of the basin to absorb and filter excess nursery water. Grasses, groundcovers and shrubs have been added to the higher parts of the banks for aesthetics and to create habitat for native animals.
Conservation, Education and Research
• Raise awareness with visitors and provide educational opportunities for students.
• Protect natural systems including streams and wetlands by improving water use and quality of surface and groundwater run-off on site.
• Provide ecological benefits for terrestrial and aquatic biodiversity.
• Evaluate the effectiveness of plants for form, function, longevity, and aesthetic appeal in stormwater treatment systems.