Paddock’s Wetlands, Salisbury City, South Australia
<< Return to introduction
The Paddock’s Wetlands is a good example of an integrated
wetland and stormwater management system combined with public open
space that has stood the test of time. This was benchmark project
not only for wetlands development but for aquifer storage in Australia. The
wetland is also unusual as it was ephemeral, as most constructed
wetlands have permanent water bodies.
Salisbury City is located 25 kilometres north of Adelaide, in Australia’s
driest state. The city experiences a mediterannean climate
with cool wet winters and warm hot summers. Annual rainfall
for the region ranges between 400mm near the coast to 516mm along
the Para Escarpment.
Urbanisation of Salisbury developed rapidly post WW2, resulting
in an unattractive landscape. Much of the original low woodland
vegetation had been cleared with remnants surviving on hills and
gullies.
The original 46 hectare site was degraded farmland adversely affected
by stormwater from the nearby Para Hills residential area. During
Winter stormwater discharged into the paddocks causing local flooding. The
Paddocks is underlain by a shallow water table (less than 500mm below
the ground) which caused extensive areas of bare salt scalds.
Residential development had been proposed for the site, known as
the Para Hills Paddocks. The community objected to the proposal
and the 46 hectare site was marked for open space and recreation
use. During the public consultation process, the community
expressed their desire for a range of features, these included, playing
fields and courts as well as water bodies and natural bushland.
Barrie Ormsby, the Principal Landscape Architect for Salisbury Council,
designed the scheme and was responsible for construction supervision
and ongoing management of the site. In the early 1970’s
projects of this type were scarce in Australia. For Ormsby
it was a ‘learning process’ where he sought inspiration
from natural landscapes and systems (pers comm.).
Construction began in 1975, with an extensive tree planting program
starting two years later. Built infrastructure identified during
community consultation was completed in 1977. During the life
of the project the wetlands have been extended a number of times
and now cover over 6 hectares.
Above ground drainage was integrated with the landscape design. Stormwater
was contained by a series of natural creeks, ponds, wetlands, detention
basins and mounds. These measures cost the same as a traditional
engineered system, however have a much higher value in terms of creating
recreation opportunities and natural habitats within the urban fabric.
The wetlands are ephemeral, drying out during times of low rainfall. This
is a natural condition for semi-arid and arid areas. The majority
of the wetlands are shallow, with water levels less than one metre
and usually dry out during the Summer months. Many wetland
plants are adapted to these cycles and are able to germinate as the
water recedes. Ephemeral wetlands are often more biologically
productive than permanent ones.
Aquifer storage
In 1994, in an attempt to rectify
the cities huge irrigation costs, the first experimental Aquifer
Recharge Bore was tested. During
the high rainfall Winter period excess stormwater entering the wetlands
is injected and stored in the aquifer. Aquifers are a layer
of rock or sand which can hold water and in the case of the Paddocks
is 164 below ground. Water is pumped out for irrigation of
the turf and sports areas of the Paddocks during the dry summer months.
This trial conducted by the Salisbury City Council and Mines and
Energy, South Australia was successful.
Thirty years on, the Paddocks Wetlands
is an established mosaic of aquatic and terrestrial habitats. It is home to a variety
of nectar and insect feeding birds, native fish, frogs, yabbies and
aquatic invertebrates. Water from the wetlands supports River
Red Gums and Swamp Oaks. The passage of stormwater is slowed
through the system and pollutants are removed providing quality water
for downstream ecosystems.
The Paddocks is one of 36 wetlands within the City of Salisbury,
with the City recognized as a world leader in wetlands technology.
Prepared by Edwina Richardson (AAILA)
2006
<< Return to introduction
REFERENCES
City of Salisbury (no date) “Stormwater Management” brochure
City of Salisbury (no date) “The Paddocks Wetlands” brochure
Ormsby, B (2005) pers comm
