Water quality in karstlands at Mole Creek, Tasmania

Samples from 28 sites at Mole Creek were analysed for a range of water quality indicators. Low or negligible bacterial counts were obtained for sites with mainly forested catchments; cleared catchments gave more variable and generally higher results. Higher turbidity and nitrate levels were recorded in cleared catchments, suggesting increased erosion and nutrient loading of streams. A comparison of water quality parameters at streamsinks and related springs shows that the karst aquifer is not an efficient water purifier. Rapid capture of surface run off via solutional openings, coupled with the pipe-like efficiency with which karst conduits transfer the water, constrains the potential for the karst aquifer to ameliorate water pollution problems. This connection between surface and underground environments is a key consideration for sustainable land management in karstlands. We conclude that karst aquifers have more in common with surface streams than non-karstic ground-water systems, in terms of their water purification properties. Water from two bores was found to be relatively free of microbiological pollution, despite being located in disturbed catchments. This suggests that ground-water sourced from bores is less affected by activities at the surface, although further work is required to confirm this

Notes on the geology and geomorphology of De Witt Island, southwest Tasmania

De Witt Island, off the south coast of Tasmania, is composed of a folded succession of turbiditic silstone, sandstone and conglemerate, at least 450 m thick. It is probably a correlate of the Mid to Upper Cambrian Ironbound Group. Folds are upright, open to tight and at least two generations are indicated. The broad-scale geomorphology of the island is controlled by the direction of storm waves which have eroded nearly vertical cliffs up to 340 m high on the south shore. Many sea caves are found at the base of the cliffs, particularly on the west and south coasts. Cliff retreat has progressively captured the headwaters of the island's two perennial streams. Fluvial processes, controlled by both lithology and structure, but also showing possible influence from interglacial and glacial stages, have shaped the interior of the island for a long period. Aeolian processes have deposited sand sheets in the island's central basin. Some well-developed pseudokarst systems, including sinkholes, caves, underground drainage and airflows, are related to large rotational slumps on the island's south coast