Ewens Ponds (South Australia)
Encyclopedia
Ewens Ponds are a series of three limestone
sinkholes on Eight Mile Creek 25 kilometres (15.5 mi) south of Mount Gambier
and 5 kilometres (3.1 mi) east of Port Macdonnell, South Australia
. The ponds are popular with scuba divers
, with underwater visibility of up to 80 metres (264 feet) and a large fish population including the endangered golden pygmy perch.
of the "Boandik" tribe, part of a larger "Bunganditj" clan. The first European identified with the area was Thomas Ewens, whose dog chased a kangaroo into one of the ponds. The land surrounding the ponds was gradually cleared for agriculture and dairy farming and a drainage system built to draw water from the ponds for land sold for soldier settlement
programs post-World War II
.
In 1978 a trout
farm was established utilising the waters flowing through Ewens Ponds. Although the ponds themselves are now part of a conservation park, the farm continues to operate. Water for the farm is drawn from the second pond, and wastewater discharged back into Eight Mile Creek downstream from the pond system.
approximately nine metres (30 feet) deep and connected to the others by shallow watercourses called "races". The beds are covered with a fine silt layer and the floor of the third pond also contains a natural shallow cave. The ponds are located in a narrow band of native bush land, surrounded by cleared terrain. The landscape is characteristic of karst topography
, shaped by the gradual dissolution of soluble limestone to form hollows and small caves, along with numerous large and relatively deep sinkholes (true cenotes).
The ponds contain extremely clear, high quality freshwater in which snorkellers and scuba divers can enjoy the wonder of swimming in a giant 'underwater garden', where the prolific plant life can easily be seen on the far side of each pond, more than 80 metres away in some areas. The clarity of the water also allows sufficient sunlight to penetrate that plant growth on the pond beds can reach up to six metres in height. The ponds are also occasionally affected by outbreaks of blue-green and other algae, though testing has found no evidence of health risks. In 2007 the South Australian Environmental Protection Agency suggested the algal blooms may be a result of continued concentrations of soluble nitrogen
in both the ponds and the adjoining Eight Mile Creek, arising from infiltration of the groundwater by fertilisers, animal waste or wastewater.
, river blackfish
, pouched lampreys, mullet
and common galaxias
. The ponds are also home to populations of flatworm
s, freshwater crayfish
and mussel
s, and the larva of the carnivorous caddis fly.
High underwater visibility, the presence of rare and interesting fish, invertebrates and plants and the ponds' unique photographic potential have made them popular with scuba divers. Of particular interest in these clear waters is the actual observation of photosynthesis - aquatic plants can be seen releasing thin trails of bubbles as they convert sunlight into oxygen. However divers are prohibited from entering caves or crevices on the pond beds and strongly discouraged from disturbing the silt layer
as the resulting turbidity
may harm plant life. Divers enter at the First Pond, drift with the current through the First Race to the Second Pond, and then continue through the Second Race to the Third Pond before exiting the water via a ladder there. However, some divers (especially snorkellers) occasionally attempt to vigorously swim upstream through the races to return to Ponds One or Two, thereby disturbing the water plants lining the races, and this practice is strongly discouraged by the diving community. The general water temperature of the ponds is around 15 °C (60 °F).
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
sinkholes on Eight Mile Creek 25 kilometres (15.5 mi) south of Mount Gambier
Mount Gambier, South Australia
Mount Gambier is the largest regional city in South Australia located approximately 450 kilometres south of the capital Adelaide and just 17 kilometres from the Victorian border....
and 5 kilometres (3.1 mi) east of Port Macdonnell, South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
. The ponds are popular with scuba divers
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
, with underwater visibility of up to 80 metres (264 feet) and a large fish population including the endangered golden pygmy perch.
History
The original inhabitants of the land were AboriginesIndigenous Australians
Indigenous Australians are the original inhabitants of the Australian continent and nearby islands. The Aboriginal Indigenous Australians migrated from the Indian continent around 75,000 to 100,000 years ago....
of the "Boandik" tribe, part of a larger "Bunganditj" clan. The first European identified with the area was Thomas Ewens, whose dog chased a kangaroo into one of the ponds. The land surrounding the ponds was gradually cleared for agriculture and dairy farming and a drainage system built to draw water from the ponds for land sold for soldier settlement
Soldier settlement (Australia)
Soldier settlement refers to the occupation and settlement of land throughout parts of Australia by returning discharged soldiers under schemes administered by the State Governments after World Wars I and II.- World War I :...
programs post-World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
.
In 1978 a trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
farm was established utilising the waters flowing through Ewens Ponds. Although the ponds themselves are now part of a conservation park, the farm continues to operate. Water for the farm is drawn from the second pond, and wastewater discharged back into Eight Mile Creek downstream from the pond system.
Geography
Each pond is a basin-shaped limestone dolineDoline
Doline can refer to:* Doline , a village in the Kanjiža municipality, Serbia.* Sinkhole, a natural depression or hole in the surface topography caused by the removal of soil or bedrock, often both, by water....
approximately nine metres (30 feet) deep and connected to the others by shallow watercourses called "races". The beds are covered with a fine silt layer and the floor of the third pond also contains a natural shallow cave. The ponds are located in a narrow band of native bush land, surrounded by cleared terrain. The landscape is characteristic of karst topography
Karst topography
Karst topography is a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite, but has also been documented for weathering resistant rocks like quartzite given the right conditions.Due to subterranean drainage, there...
, shaped by the gradual dissolution of soluble limestone to form hollows and small caves, along with numerous large and relatively deep sinkholes (true cenotes).
The ponds contain extremely clear, high quality freshwater in which snorkellers and scuba divers can enjoy the wonder of swimming in a giant 'underwater garden', where the prolific plant life can easily be seen on the far side of each pond, more than 80 metres away in some areas. The clarity of the water also allows sufficient sunlight to penetrate that plant growth on the pond beds can reach up to six metres in height. The ponds are also occasionally affected by outbreaks of blue-green and other algae, though testing has found no evidence of health risks. In 2007 the South Australian Environmental Protection Agency suggested the algal blooms may be a result of continued concentrations of soluble nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
in both the ponds and the adjoining Eight Mile Creek, arising from infiltration of the groundwater by fertilisers, animal waste or wastewater.
Fauna
The ponds are one of only three recorded locations for the golden pygmy perch (Nannoperca variegata). Other fish life includes schools of short-finned eelShort-finned eel
The short-finned eel, Anguilla australis, is one of the 15 species of eel in the family Anguillidae. It is native to the lakes, dams and coastal rivers of south-eastern Australia, New Zealand, and much of the South Pacific, including New Caledonia, Norfolk Island, Lord Howe Island, Tahiti, and...
, river blackfish
River Blackfish
The river blackfish, is an Australian native freshwater fish of the Murray-Darling river system, found from southern Queensland through to central Victoria. It is also found in some eastern and southern flowing coastal rivers...
, pouched lampreys, mullet
Mullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
and common galaxias
Common galaxias
The common galaxias or the inanga , is a species of fish from the galaxiid family that is very widespread in the southern hemisphere. It is a slim narrow fish with a forked tail and as an adult it lives in freshwater rivers and lakes. Common galaxias grows to a length of 40 to 120 mm, but can grow...
. The ponds are also home to populations of flatworm
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
s, freshwater crayfish
Crayfish
Crayfish, crawfish, or crawdads – members of the superfamilies Astacoidea and Parastacoidea – are freshwater crustaceans resembling small lobsters, to which they are related...
and mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s, and the larva of the carnivorous caddis fly.
Recreational activities
The ponds are owned by the South Australian Government's Department of Water, Land and Biodiversity Conservation and are managed as a conservation park by the Department of Environment and Heritage. Plant and animal species in the ponds are protected and may not be removed.High underwater visibility, the presence of rare and interesting fish, invertebrates and plants and the ponds' unique photographic potential have made them popular with scuba divers. Of particular interest in these clear waters is the actual observation of photosynthesis - aquatic plants can be seen releasing thin trails of bubbles as they convert sunlight into oxygen. However divers are prohibited from entering caves or crevices on the pond beds and strongly discouraged from disturbing the silt layer
Silt out
A silt out is a situation when underwater visibility is rapidly reduced to zero.It often happens from divers' swimfins disturbing silt, particularly in caves or in still fresh water....
as the resulting turbidity
Turbidity
Turbidity is the cloudiness or haziness of a fluid caused by individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality....
may harm plant life. Divers enter at the First Pond, drift with the current through the First Race to the Second Pond, and then continue through the Second Race to the Third Pond before exiting the water via a ladder there. However, some divers (especially snorkellers) occasionally attempt to vigorously swim upstream through the races to return to Ponds One or Two, thereby disturbing the water plants lining the races, and this practice is strongly discouraged by the diving community. The general water temperature of the ponds is around 15 °C (60 °F).