Topography & Climate

The tenement area (EPC 987) is located in the Desert Uplands bioregion, an area of about 70,300 km2, which lies in central northern Queensland. The term ‘desert’ is usually associated with areas of little or no vegetation.  However the Desert Uplands bioregion is thickly vegetated and the term has perhaps been used because there is an abundance of spinifex (Triodia spp.) which is a grass commonly associated with the more arid regions of Australia.

 

The bioregion straddles the Great Dividing Range between Blackall and Pentland and is dominated by sandstone ranges and sand plains (Figure Below). Barcaldine and Aramac are the major population centres and Prairie, Torrens Creek, Pentland and Jericho are smaller centres within the region.

 

The climate is semi-arid with variable summer-dominant rainfalls. The bioregion is too far north to receive reliable winter rain and too far south to receive monsoonal wet periods typical of northern Australia. In general, there is a decline in rainfall from east to west, correlating with two broad categories of vegetation types: Brigalow dominant scrubs in the east; and Gidgee Blackwood and open grasslands in the far west.

 

The mean annual rainfall ranges from approximately 400 mm to 800 mm. The mean daily summer temperature for Barcaldine ranges from 23° C to 35.8° C. The mean winter temperatures for Barcaldine ranges from 7.7° C to 22.5° C.

 

Desert Uplands landforms are the remnants of ancient, deeply weathered plateaus made up of plains gradually sloping to alluvial frontages with occasional steeper areas fronting the lower ranges and escarpments. It is this lower eastern area that is the focus for shallower coal exploration under Tertiary age sediments.

 

The Great Dividing Range forms a low watershed in most of the bioregion (Figure Below). The main waterways draining the Desert Uplands are the Belyando, Cape, Campaspe, Barcoo and Alice Rivers and the Aramac and Torrens Creeks. Two significant internal drainage basins in the centre of the region form the catchments of Lake Galilee and Lake Buchanan. These brackish lakes only fill in above average wet seasons. Drainage in the EPC 987 area is associated with Belyando Creek tributaries.

 

The bioregion lies on the eastern margin of the Great Artesian Basin and parts of it are important intake areas for the aquifer of the basin. The bioregion partly lies within the Galilee and Eromanga Basins. These basins consist of Mesozoic to Tertiary (less than 251 million years ago) sediments including major coal and gas deposits.

 

The bioregion consists of predominantly sandy, infertile and poorly-structured soils. Most of the sandy soils are red in colour but sandy yellow soils are widespread in the north. These soils are very well drained, which decreases water availability for plants during long, dry periods.

 

 

Figure  Topography & Drainage near EPC 987

 

 

 

Texture contrast soils with sandy surfaces are common on the lower slopes and in depressions.

 

Uniform clay soils occur, to an extent, in association with old lakebed deposits and as extensions of the western plains into the Desert Uplands bioregion. These clay soils expand when wet and crack when dry.  While soils are reasonably fertile, vegetation growth is limited by rainfall. The soils in general are very low in essential mineral and trace elements, particularly phosphorus. Despite these limitations, the soils support a diverse range of native plant species.

 

Where slopes occur within the bioregion, the sandy top soils are prone to sheet erosion caused by water.  Hardpans restrict the movement of water and the growth of plant roots increasing the potential risk of erosion occurring. With respect to exploration operations, following periods of significant rain, access is restricted due to isolated areas retaining moisture for long periods  which limits the movement of vehicles and equipment.

 

Europeans first settled in the area in the 1860s and 1870s spreading from established holdings in more fertile land further east and west. These early settlements were predominantly part of closer settlement initiatives and proved too small to be viable. The climatic conditions of the area, along with commodity price pressures, production costs and invasions by pest species made it difficult for these early Europeans to sustain a profitable enterprise from the land. This appears to be an ongoing story for the Desert Uplands.

 

Today, the majority of land tenure is leasehold (about 80%) with the remainder comprising freehold, reserves and other tenures in small parcels of land.

 

Cattle grazing on native pastures is the main land use in the surrounding area. However pasture development with buffalo grass (Cenchrus ciliaris) following clearing for more intensive cattle production has been undertaken, predominantly  on the better soils carrying Acacia forests. In more recent times more clearing of eucalypt woodlands on the infertile soils has been occurring. Some sheep grazing for wool production is currently undertaken in the western areas of the region.