The Cooper subregion lies across the SA–Queensland border (including a small area of NSW at Cameron Corner), occupying approximately 130,000 km2 (Figure 4). The subregion is generally flat, with dunes in the south-west. The topography ranges from –10 to 473 mAHD and is characterised by the braided channels of Cooper Creek and the Barcoo River, with very few lakes and salt lakes. More information on the surface water features of the subregion is provided in Section 1.1.5 .
The Cooper subregion is located in the Lake Eyre drainage catchment. Most (approximately 118,500 km2) of the Cooper subregion sits within the Cooper Creek – Bulloo river basin although a small part (approximately 11,500 km2) in the north-west of the subregion sits within the Diamantina–Georgina river basin.
A physiographic region is defined as a discrete morphological unit with internal coherence of its landform characteristics (Jennings and Mabbut, 1977). Physiographic regions are defined and mapped by landform characteristics that reflect uniform landform evolution, underlying geology and contained regolith materials (Pain et al., 2011). Early, largely descriptive, state-based treatments of Australian physiography that included Victoria (Hills, 1940) and WA (Jutson, 1914) progressed to continental-scale physiographic mapping by Jennings and Mabbut (1977) using improved topographic maps and other data. Physiographic mapping is descriptive and provides a regional-scale classification of landforms and related physical geography as they reflect underlying geological and climate controls. The most recent national-scale physiographic mapping by Pain et al. (2011) extends the mapping of Jennings and Mabbut (1977) by utilising the Shuttle Radar Topography Mission (SRTM) digital elevation model and other new data such as national and state soil and land survey data in a GIS mapping system. The classification has three divisions at the broadest level, 23 provinces distinguishing major physiographic changes, and 220 regions forming the basic subdivision of internally consistent landform morphology and inferred origin (Pain et al., 2011).
Five main physiographic regions cover the Cooper subregion (Figure 5). From south-west to north-east, these are the Strzelecki Desert Plains, Innamincka Plains, Sturt Desert Plains, Cooper Plain, and the Eromanga Lowlands. A sixth region (Winton-Blackall Downs, 20201) is mapped in the north-easternmost corner of the subregion, while a seventh (Grey Range, 20221) is present over a very small portion of the south-east of the subregion. Region descriptions from Pain et al. (2011) for these physiographic regions are provided in Table 3.
Table 3 Physiographic region descriptions for the Cooper subregion
Data: Pain et al. (2011)
Data: CSIRO (Dataset 5)
Region identification numbers are as used by Pain et al. (2011)
Figure 6 shows the Cooper subregion soils derived from the Australian Soil Classification (Isbell, 2002). This hierarchical classification features the B horizon characteristics and provides an assessment of the agricultural potential of the soil.
The Cooper Plain has Vertosols which are clay-rich soils characterised by shrink-swell properties that produce both strong cracking when dry and gilgai microrelief at the surface and slickensides and lenticular aggregates at depth. Gilgai microrelief is an irregular, generally polygonal pattern of alternating mounds and depressions, at variable scales, produced by physical subsoil movements in alternate shrink-swell cycles due to wetting and drying. Soil properties and profiles of gilgai mounds and depressions can vary. Vertosols have high agricultural potential with high fertility, variable structure depending on wetting state, and good water-holding capacity (Isbell, 2002). Vertosols are also characteristic of the Innamincka Plains.
The Eromanga Lowlands has a mix of Vertosols, Sodosols, Tenosols, and Kandosols. Sodosols show strong texture contrast with a highly sodic B horizon and pH greater than 5.5. They generally form on highly to moderately siliceous parent material and generally have low agricultural potential, low to moderate fertility, poor structure, low permeability, high erodibility and soil salinity. Sodosols are also characteristic of the Sturt Desert Plains. Tenosols are a diverse range of weakly developed sandy soils with an A horizon and are generally formed on highly siliceous parent materials. They tend to have low agricultural potential, low fertility, poor structure and low water-holding capacity. Kandosols are non-calcareous soils that lack a strong texture contrast and are developed on highly siliceous to intermediate parent material. They have low to moderate agricultural potential with moderate fertility and water-holding capacity (Isbell, 2002).
The Strzlecki Desert Plains are characterised by Rudosols and Kandosols. Rudosols are young soils with minimal pedogenic organisation and can vary widely in terms of texture, structure and depth. The Innamincka Plains also contains Rudosols.
220.127.116.11.3 Land cover
Figure 7 shows the dynamic land cover distribution across the Cooper subregion derived from Geoscience Australia remote sensing mapping which uses a time series analysis of 34 structural vegetation classes ranging from cultivated and managed land covers (crops and pastures) to natural land covers (forests and grasslands) (Lymburner et al., 2011).
The subregion is characterised by sparse shrubs, sparse hummock grass and scattered grassland; distributions of which do not seem much related to soils or physiographic regions. The most striking land cover feature is the distribution of tussock grasses which closely matches the Vertosols of the Cooper Plain.
Data: Geoscience Australia (Dataset 9)
Product Finalisation date
- 1.1.1 Bioregion
- 1.1.2 Geography
- 1.1.3 Geology
- 1.1.4 Hydrogeology and groundwater quality
- 1.1.5 Surface water hydrology and water quality
- 1.1.6 Surface water – groundwater interactions
- 1.1.7 Ecology
- Contributors to the Technical Programme
- About this technical product