On average, the Adelaide metropolitan area generates around 86 gigalitres of stormwater per year. Much of this is discharged to the sea, with less than 10% currently being re-used. If this seems like a great waste of water, you are right!
The NRM Board recognizes the great potential that stormwater can provide if we are to more effectively manage our available water resources. Consequently, the Board works with stakeholders, such as local government to investigate and develop opportunities for putting stormwater to good use.
However, before stormwater can be harvested and used, it must be cleaned up. As stormwater moves across surfaces such as roads, roof tops, and gardens etc it picks up a concoction of harmful pollutants such as heavy metals, chemicals, nutrients and sediments. Some of these you can see, others you can’t.
Constructed Wetlands
Wetlands are nature’s water purifier. Heavy particles, such as soil, fall to the bottom taking with them some of the chemicals. Water plants such as reeds and floating plants absorb the nutrients. Any bacteria accumulating in the wetland, is killed by the sun's ultra-violet rays.
In addition to the water quality benefits that are provided by wetlands, they can also provide aesthetic and recreation value, provide habitat for native animals and assist in flood management.
Over the years, before the benefits of wetlands were fully understood, many natural wetlands on the Adelaide Plains were drained and replaced by urban developments.
The NRM Board is now partnering with stakeholders to build constructed wetlands in key locations for the purpose of capturing and purifying storm water.
ASR – Aquifer Storage and Recovery
In some situations, constructed wetlands are developed simply to purify stormwater and / or to mitigate against flooding. In certain situations, wetlands can also play an important role in capturing stormwater such that it can be used at a later time.
While wetlands are ideal water purifiers, they do not make great reservoirs. Water accumulates in the wetland during periods of rain and evaporates out of them during the hotter drier months. Therefore in the summer, when the water is most needed, there is little water available. To overcome this, Aquifer Storage and Recovery Schemes (ASR) are used to maximize their water storage efficiency.
As the wetland becomes inundated with water, the clean water is pumped underground into a natural aquifer where it is stored. This stored water can then be pumped back up to the surface where it can then be used for purposes such as for irrigation or for industry.