AT THE POINT
Location: This confluence point is located in western Queensland, on the property ‘Merrigal'. The closest settlement is Yaraka, approximately 15 km to the north-east. While the confluence itself is unmarked, a GPS was used to find the exact location (accurate to within a few metres). Access to near the point is via property tracks. The site was visited in the mid morning by a party of RGSQ members travelling in 4WD vehicles from Brisbane in November 2009. The point lies within Barcoo Shire.
The Landscape: Elevation at the degree confluence is 203 m, and the view shows a flat surrounding landscape. Surface material is a sandy/clay loam with some gibber coverage, and vegetation is reasonably dense mulga and low scrub. There were no animals sighted near the confluence, and the property ‘Merrigal' has been de-stocked. Significant human features nearby include infrastructure of the property, such as fences, roads, and the homestead next to Mills Creek.
The confluence is subject to inundation from the closest watercourse, Mills Creek after which the degree square is named, approximately 1 km to the south-west. The geology at the confluence is Winton Formation sediments such as Albian age sandstone, mudstone and siltstone (100 million years), while the course of nearby creeks is undifferentiated Quaternary alluvium (less than 1.6 million years).
Point information and photos: Paul Feeney with additions by Jo Grant, 2009
WITHIN THE DEGREE SQUARE
The Country: The landscape of the square is dominated by the floodplain of the Barcoo River and the hills of the Grey Range to the east. Elevations range from around 400 m ASL in the Gowan Range to around 100 m ASL where the Barcoo exits the square.
Much of the square is composed of sandstone and other sedimentary rocks of the Winton Formation that dates from Albian times (100 million years). This formation is often weathered into a landscape of mesas and scree slopes. In the south-east corner of the square the Winton Formation gives way to the Glendower Formation sandstone of Late Palaeocene age (around 55 million years).
Mesas and rubble scree slopes in the Winton Formation (Paul Feeney, 2009)
Vegetation across the square is similar to that at the point with grasslands and stands of mulga dominating. Riparian communities along the watercourses are dominated by Coolibah and River Red Gum.
Land use is dominated by sheep and cattle grazing with scattered small-scale mining (much of which has been abandoned).
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The Climate: The climate of the area is classified as hot grassland with a winter drought. The Bureau of Meteorology climate station at the Isisford Post Office provides representative statistics. The variability of the rainfall and temperatures may be seen in the table.
Isisford Post Office (036026) 1885-2010 (elevation 203 m ASL)
The highest temperature ever recorded in Longreach was 47.0° in January 1973 while the lowest temperature -2.0° in August 1974. Rainfall also varies greatly. The highest total of 1309.1 mm was recorded in 1950 and the lowest total of 125.3 mm in 1938.
Extremes of Nature: The cyclone database maintained by the Bureau of Meteorology shows seven active or former cyclones have tracked within 200 km of the confluence point since 1906. Of these, two passed within 50 km of the point: an unnamed cyclone in January 1913; and TC Althea in December 1971. All of these storms brought heavy rain falls that produced flooding in both local and regional catchments.
Cyclone tracks within 200 km of point 1906 to 2006 (Bureau of Meteorology web site)
The area receives between 20 and 25 thunder days on average each year. The more severe thunderstorms can produce destructive winds, intense rainfall that may cause localised flash flooding, and lightning strikes may spark bushfires if there is sufficient fuel for it to spread.
Records of large floods in the Barcoo and other streams in the area extend back as far as the late 19th century, with the most significant episodes of flooding occurring in 1893, 1906, 1949, 1955, 1963, 1974, 1990 and 2000. In most instances floods in this area bring more benefits than damage as they tend to replenish soil moisture. They are generally slow moving and forecasts permit the movement of stock and other property to flood-free areas. Floods can, however, cut roads and isolate properties for lengthy periods.
Sunrise after the storms
Drought and heatwave remain the most frequent and severe natural hazards. Isisford averages 99 days a year (50 years of records) with temperatures of 35oC or more and 20 days a year with temperatures of 40oC or greater. Heatwaves kill more people in Australia than all other natural hazards combined.
The National Earthquake Database maintained by Geoscience Australia contains no event epicentres within the degree square.
The Indigenous Story: Most of the land within the degree square is the traditional country of the Kuungkari people.
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European Exploration and Settlement: The first European to pass through this area was Edmund Kennedy in 1847 and again in 1848. Graziers with their flocks of sheep moved into the area in the 1860s.
In 1910 the State Government authorised the building of 1282 miles (2060 km) of railway in western Queensland to support the pastoral industry. Only a quarter of the line was built and Yaraka became ‘the end of the line'. Settlements like Yaraka and Emmet grew as railway camps and prospered for a time. At its peak from 1917 to around 1930 Yaraka had a population of 100 but today has joined the ranks of Queensland's ‘vanishing towns'.
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The total population of the degree square at the 2011 national Census was 215. The apparent fluctuation in population is due to changes in census boundaries rather than an actual ‘boom’ between 1996 and 2011.
Land use across the square is predominantly grazing of either cattle or sheep.
There are 1120 km of public roads within the square and many other kilometres of private roads on properties. The railway line as far as Yaraka remains serviceable. Many properties also have their own airstrips for light aircraft.
Local road near the confluence point (Paul Feeney, 2009)
There are sections of the Welford National Park in the west of the square and a small section of the Hell Hole Gorge National Park in the south of the square. The square covers parts of three local government areas - Quilpie Shire in the south and south-east, Longreach Regional Council in the north-east and Barcoo Shire through the centre and west.
Edited by: Hayley Freemantle
Compiler: Ken Granger, 2010
References: various web sites including EPA, local governments, tourist industry and Bureau of Meteorology.
Queensland Museum, 2003: Discovery guide to outback Queensland, Queensland Museum, Brisbane.