Stormwater harvesting could help recharge aquifers
Released 01 Dec 2008
There are a number of options for better managing stormwater - according to a report commissioned by the Department of Water.
The study focused on main drains in the coastal area, the Swan-Canning catchment and the Peel region.
The report assessed how much stormwater is currently discharged to the rivers and ocean via the existing drainage system, and looked at better management options.
The Department of Water's Director of Water Resource Management, John Ruprecht said Perth's metropolitan region had about 830 kilometres of main drains and 3000 kilometres of local drains.
"The report estimates that there is an annual discharge of about 120 gigalitres of water from these drains," he said.
"Of this, two-thirds flows from the Swan–Canning main drains, 20.6 gigalitres from the Peel drains and 18 gigalitres from the coastal (Carine, Herdsman and Subiaco) drains.
"This stormwater volume is equal to twice the full storage capacity of the Mundaring Weir or 2.5 times the annual production from Perth's desalination plant.
"One way of better managing this stormwater could be by modifying main drainage channels and maximising the recharge of aquifers by using water sensitive urban design principles.
"Converting these drains to living streams could also enhance the quality of the stormwater."
Mr Ruprecht said the current Cottesloe Peninsula Groundwater Restoration Project was a positive example of water sensitive urban design principles being used to harvest stormwater. In this case, stormwater outlets have been replaced with new soakage pits that trap and filter stormwater to replenish the aquifer.
In Salisbury, South Australia, a modified drainage network has been used to treat slow flows and store stormwater before supplying it to industry.
"While the department supports the concept of stormwater harvesting, the impact on the environmental flow requirements of river systems would need to be considered," Mr Ruprecht said.
"The report suggests that prior to harvesting, further ecological studies of wetland and waterway systems within drain catchments should occur."
Contact: Dianne Dixon
Phone: (08) 6364 6983 / 0419 910 847