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Directory of Important Wetlands

Directory of Important Wetlands in Australia - Information sheet

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Onkaparinga Estuary - SA033

Level of importance: National - Directory
Location: 35 degrees 00' S, 138 degrees 49' E; Fleurieu Peninsula, situated 35 km south of Adelaide between the townships of Noarlunga and Port Noarlunga on the eastern side of Gulf St Vincent. This listing includes the Onkaparinga Estuary and 5 lagoons adjacent to the main channel: Onkaparinga 2 - 35 degrees 9' 31" S, 138 degrees 28' 48" E; Onkaparinga 3 - 35 degrees 10' 35" S, 138 degrees 29' 49" E; Onkaparinga 4 - 35 degrees 10' 12" S, 138 degrees 29' 50" E; Onkaparinga 5 - 35 degrees 9' 20" S, 138 degrees 29' 39" E and Onkaparinga 6 (two lagoons) - 35 degrees 9' 15" S, 138 degrees 29' 31" E and 35 degrees 9' 16" S, 138 degrees 29' 21" E.
Biogeographic region: Flinders Lofty Block
Shire: Onkaparinga
Area: 70 ha.
Elevation: 0-15 m ASL.
Other listed wetlands in same aggregation: None.
Wetland type: A1, A2, A8, A7, A6
Criteria for inclusion: 1, 3, 6,
Site description:
The Onkaparinga estuary extends 10.5 km inland from its mouth along the coast at Port Noarlunga, to a deep pool or oxbow lagoon adjacent to Noarlunga township (Onkaparinga 3). The area is comprised of three major habitat types: the upper tidal reaches of the river; the lagoon/floodplain habitat in the lower reaches of the estuary; and the remnant sand dunes near the river mouth. The floodplain of the estuary is characterised by samphires and areas of sandy marine and estuarine mud flats which are in part colonised by seagrass.
Physical features:
Landform: Wide meandering river channel, broad flat floodplain, seagrass meadows, samphire marshes and coastal sand dunes. Climate: Mainly receives a winter rainfall with most rain falling from April- October, total 600 mm.
Hydrological features:
Water supply: The estuary is tidal as far as the township of Noarlunga. During the summer months the estuary receives minimal freshwater flow and deposits of sand inshore close the mouth of the river, creating a lagoon in the lower portion of the estuary. Water pH: Ranges from 9.2-7.8, Jan.-Sept. 1986 (Paul Manning & Associates 1986; Edyvane in press a).
Onkaparinga 2: 15/10/01 - pH (8.25); Conductivity (11.60); Turbidity (82); Dissolved oxygen (12.3); Water temperature (23 degrees C) (Seaman 2002d).
Ecological features:
Ecological role: The estuary is a spawning area for Black Bream (Acanthopagrus butcheri), and a nursery area for Yellow-eye Mullet (Aldrichetta forsteri). Provides areas of shallow water, such as the samphires and mudbanks which are important feeding grounds for many waders, swans and pelicans. Plant structural formations: Samphire low shrubland with associated chenopods and sedges; heath and low open shrubland on coastal dunes.
Significance:
The Onkaparinga estuary comprises an environment which is not common elsewhere in Australia. The Onkaparinga River is the second largest permanent river in South Australia, and its estuary is the third largest in extent after the Murray/Coorong and Port Adelaide River estuary systems. The halophytic community within the area is the only example of this community type south of Adelaide along the eastern shores of Gulf St Vincent.
Notable flora:
Threatened species: Twenty-two species occur within Onkaparinga Recreation Reserve with conservation significance; these include: Angianthus preissianus (salt angianthus) Rare Southern Lofty, Apium annuum (annual celery) Rare Southern Lofty, Austrofestuca littoralis (coast fescue) Rare Southern Lofty, Carex bichenoviana (notched sedge) Uncommon Southern Lofty, Crassula helmsii (swamp crassula) Rare Southern Lofty, Diplachne parviflora (small-flower beetle-grass) Rare SA, Gahnia filum (smooth cutting-grass) Rare Southern Lofty, Gnaphalium indutum (tiny cudweed) Rare Southern Lofty, Haloragis aspera (rough raspwort) Rare Southern Lofty, Lavatera plebeia (Australian hollyhock) Uncommon Southern Lofty, Lotus australis (austral trefoil) Uncommon Southern Lofty, Maireana decalvans (black cotton-bush) Endangered Southern Lofty, SA, Maireana enchylaenoides (wingless fissure-plant) Uncommon Southern Lofty, Melaleuca halmaturorum (swamp paper-bark) Vulnerable Southern Lofty, Myoporum parvifolium (creeping boobialla) Vulnerable Southern Lofty, Rare SA, Samolus repens (creeping brookweed) Uncommon Southern Lofty, Schoenoplectus pungens (spiky club-rush) Uncommon Southern Lofty, Schoenus nitens (shiny bog-rush) Rare Southern Lofty, Selliera radicans (shiny swamp-mat) Rare Southern Lofty, Stipa eremophila (rusty spear-grass) Uncommon Southern Lofty, Wilsonia humilis var. humilis (silky wilsonia) Uncommon Southern Lofty (Seaman 2002d). Composition: Downstream from Noarlunga, reeds fringe the channel with mats of filamentous algae Enteromorpha compressa, Spirogyra transeauana and Spirogyra sp. aff. marvillosa; the mud banks in the lower reaches of the estuary are dominated by Zostera muelleri; the river floodplain in the estuary is covered by a samphire low shrubland of Sarcocornia blackiana, S. quinqueflora and Halosarcia halocnemoides, with associated chenopods and sedges; the sandhills are covered with a coastal dune vegetation of coastal heath and low open shrubland. Most of the vegetation has been modified as a result of stock grazing and vegetation clearance for agriculture. A sparse mosaic of remnant native vegetation communities remain (Fargher Maunsell Pty. Ltd. 1982; DENR 1993).
Notable fauna:
Threatened species: Musk Duck Biziura lobata (Sr), Cape Barren Goose Cereopsis novaehollandiae (Sr), Latham's Snipe Gallinago hardwickii (Sv) and Australasian Shoveler Anas rhynchotis (Sr). Composition: c. 50 waterbird species recorded, seven listed under treaties. Species common to the area are White-faced Herons Egretta novaehollandiae, Great Egrets Ardea alba and Royal Spoonbills Platalea regia. Migration stop-over: Records of the Latham's Snipe, Sharp-tailed Sandpiper Calidris acuminata, Red-necked Stint C. ruficollis and Common Greenshank Tringa nebularia (Fargher Maunsell Pty. Ltd. 1982; Lloyd & Balla 1986; DENR 1993).
Other Fauna:
Fishes: 23 species of fish. The major fish species inhabiting the estuary are Yellow-eye Mullet, Jumping Mullet (Liza argentea) and Black Bream; Others include (Congolli Pseudaphritis urvilli), Australian Salmon (Arripis truttacea), Southern Sea Garfish (Hyporhampus melanochir), and Bridled Goby (Gobius befrenatus) (Fargher Maunsell Pty. Ltd.; Lloyd & Balla 1986; Edyvane in press a).
Social and Cultural values:
Recreation: The estuary and the dunes at the mouth of the river are popular localities and cater for a wide variety of recreational activities, the most popular being fishing, canoeing, picnicking, bush walking, bird watching and swimming.
Land tenure:
Onsite: Public including the Onkaparinga Aquatic Reserve and Onkaparinga Recreation Park. The Recreation Park is located adjacent to the estuary between Commercial Road and Main South Road at Noarlunga and includes several of the lagoons. Surrounding: Private land and Crown land - north of the Onkaparinga mouth lies Port Noarlunga Reef (240 ha) which is a part of the Onkaparinga Estuary Aquatic Reserve, the upper reaches of the Onkaparinga River are contained within Onkaparinga River National Park.
Current land use:
Onsite: Nature conservation and recreation. Surrounding: Nature conservation, agriculture, stock grazing, heavy urbanisation and water Catchment area (Mt. Bold Reservoir).
Disturbance or threat:
Past/present: Weed infestation, visitor and recreation pressure, rubbish dumping, pollution from urban run-off and agricultural activities, rapid encroachment of urbanisation, loss of samphire flats through the construction of effluent evaporation ponds and levee banks, and the construction of Mt. Bold Reservoir has probably resulted in a reduction in the incidence of major flushing flows downstream.

Potential: Proposals to build road and railway crossings over the estuary.
Conservation measures taken:
Management plan for the Onkaparinga River Reserve prepared in 1993. The re- establishment of some degraded areas along the river and its estuary has been carried out. In 1980, sections of the reserve were planted as urban forest with 45 000 native trees and shrubs by the State Planning Authority. The Friends of Onkaparinga River Reserve have propagated and planted in excess of 50 000 native seedlings. Planting of Marram Grass (Ammophila arenaria), and the erection of drift fencing and boardwalks has been undertaken as part of the dune stabilisation programme on coastal land adjacent to the reserve.
Management authority and jurisdiction:
The Onkaparinga Estuary Aquatic Reserve is managed by S.A. Department of Fisheries. The Onkaparinga Recreation Park and National Park are managed by SA DEH.
References:
See SA Reference List
Compiler & date:
J. Morelli, S.A. Department of Environment and Natural Resources, 1995. Updated, G Anderson SA Department for Environment and Heritage, 30/5/05.
Drainage:  
AWRC Division: South Australian Gulf
AWRC Region:
AWRC Basin:
Catchment:
Sub-catchment: