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1.1 Context statement for the Clarence-Moreton bioregion

Executive summary

​Rainforest waterfall in Border Ranges National Park, NSW, 2008 Credit: Liese Coulter, CSIRO

The context statement brings together what was known about the geography, geology, hydrology and ecology of the Clarence-Moreton bioregion as at May 2014.

Geography

The Clarence-Moreton bioregion spans an area of about 24,292 square kilometres from the Lockyer Valley near Brisbane in the north, down to around 50 km south of Grafton, New South Wales. The population of the Clarence-Moreton bioregion is around 500,000 people and includes areas of the Indigenous nations, Bundjalung and Yuggera.

Geology

The Clarence-Moreton bioregion sits atop the geological Clarence-Moreton Basin. The basin covers approximately 38,000 square kilometres on-shore in south-eastern Queensland and north-eastern New South Wales. The geological basement underlying the Clarence-Moreton Basin consists of older rock sequences known as the New England Orogen. The New England Orogen formed between 505 and 210 million years ago and extends from Newcastle in New South Wales to Bowen in Queensland.

The Walloon Coal Measures is the major coal-bearing geological formation of the Clarence-Moreton Basin; it outcrops over large areas in Queensland, and mostly occurs at depths of 450 to 650 metres below the surface in the central part of the Clarence-Moreton bioregion in New South Wales. The Walloon Coal Measures formed around 165 million years ago during the Middle Jurassic period.

The Walloon Coal Measures are covered by the Lamington and Main Range volcanic rocks, which are locally up to 900 metres thick and were erupted from volcanoes and fissures that occurred between 66 million and 2.58 million years ago, during the Paleogene and Neogene geologic periods.

Surface water and groundwater

The New South Wales area of the Clarence-Moreton bioregion includes the Clarence, Richmond, Tweed and Brunswick river basins. In south-east Queensland the bioregion covers the mid and upper parts of the Logan-Albert river basin, Bremer river basin, Lockyer Valley, and parts of the mid-Brisbane river basin.

Rainfall in the river basins ranges from an annual mean of 922 millimetres for the Brisbane river basin to 1879 millimetres for the Brunswick river basin. The Clarence river basin has the largest annual runoff of all of the river basins in the bioregion. The largest water storage of the bioregion is the South East Queensland Water Grid which connects many of the river basins and population centres of south-east Queensland through more than 535 kilometres of pipeline.

The groundwater-bearing sequences in the Clarence-Moreton bioregion include shallow aquifers along river courses and floodplains and deeper formations composed of sedimentary or volcanic rocks. There are numerous alluvial aquifers in the Clarence-Moreton bioregion. Some are economically important, for example, the Lockyer Valley alluvial aquifer, which is used for irrigation and is closely managed.

Ecology

The Clarence-Moreton bioregion covers large parts of the Great Dividing Range of south-east Queensland and north-east NSW, where the steeper slopes consist of subtropical rainforest and wet sclerophyll forests. Most of these areas are protected by national parks and forest reserves. The landscape transitions through to dry sclerophyll forests and woodlands leading into the lowland areas. The lowlands and the floodplains and estuaries of the coastal regions are used extensively for agriculture and urban development.

The large floodplains in the lowlands of the Clarence river basin are of particular importance as they support many wetlands, swamps and tidal delta flats. These areas are of special conservation interest as they are home to many local and migratory bird species with at least 11 listed in international migratory bird agreements. The Clarence-Moreton bioregion is home to 432 threatened species listed under Queensland, New South Wales and Commonwealth legislation.

Last updated:
23 March 2016
Thumbnail images of the Clarence-Moreton bioregion
PRODUCT FINALISATION DATE
28 May 2014