Ewens Ponds

Ewens Ponds is a notable natural landmark in South Australia, comprising a series of three interconnected limestone sinkholes renowned for their pristine freshwater and exceptional underwater visibility. Located in the locality of Eight Mile Creek, roughly 25 kilometers south of Mount Gambier, these ponds have become a significant site for recreational diving and a crucial habitat for rare aquatic species.

Discovery and History

The ponds were first documented by Thomas Ewens, an early European settler, whose dog's pursuit of a kangaroo led to the discovery of the unique water bodies. Initially known as Thomas Ewens Spring Ponds, the area was later recognized for its ecological importance. Despite surrounding land being cleared for agriculture and dairy farming, and a drainage system being implemented, Ewens Ponds were eventually protected.

Geography and Geology

Geologically, Ewens Ponds are basin-shaped dolines formed through the dissolution of soluble limestone, a characteristic feature of karst topography. Each pond reaches a depth of approximately nine meters and is linked by shallow watercourses known as 'races'. The water is exceptionally clear, allowing sunlight to penetrate deeply and support extensive aquatic plant growth, creating what is described as a giant 'underwater garden'. The clarity of the water can exceed eighty meters in some areas.

Biodiversity

A key aspect of Ewens Ponds' significance is its role as a sanctuary for aquatic life. It is one of only three known locations for the endangered golden pygmy perch (Nannoperca variegata). The ponds also support populations of various fish species, including short-finned eels, river blackfish, pouched lampreys, mullet, and common galaxias, alongside invertebrates such as flatworms, freshwater crayfish, mussels, and caddis fly larvae.

Recreational Use and Conservation

Ewens Ponds have been managed as part of the Ewens Ponds Conservation Park since 1976. The high underwater visibility and unique aquatic environment make them a popular destination for scuba divers and snorkelers. However, strict regulations are in place to protect the delicate ecosystem, prohibiting the removal of any plant or animal species and discouraging disturbance of the silt layer. Divers typically enter at the first pond and drift through the interconnected races to the third pond, exiting via a ladder. The water temperature remains consistently around 15°C (60°F).