Yarragadee Aquifer
Encyclopedia
The Yarragadee Aquifer is a significant freshwater aquifer
located in the south west of Western Australia
and predominantly beneath the Swan Coastal Plain
west of the Darling Scarp
. It has a north-south range from about Geraldton
to the south coast, but with a split in the formation south of Perth
. The southern part is known as the South West Yarragadee Aquifer.
The aquifer is quite deep, situated hundreds of metres below ground level and with a thickness ranging up to about two kilometres.
In the Perth area, the Yarragadee Aquifer is located beneath the Leederville Aquifer, which itself is located beneath two superficial aquifers known as the Gnangara Mound
and Jandakot Mound
. These aquifers are separated by impervious layers with no groundwater called aquitards.
The Yarragadee Aquifer stores about 1000 cubic kilometres of water, compared to about 20 cubic kilometres in the Gnangara Mound. As such it is seen as a potential source of water, and the Water Corporation
of Western Australia currently extracts about 45 gigalitres
per year from the aquifer. One cubic kilometre is equivalent to 1000 GL.
Ultimately the Yaragadee Aquifer is replenished by rainfall. This recharging is usually where there are outcroppings near other aquifers like the Leederville Aquifer. There are also outcrops near the surface in the vicinity of the Blackwood River
. Current models estimate this recharge at about 280 to 340 GL per year. This groundwater can remain in the aquifer for many years; in some areas the age of the groundwater is over 30,000 years.
Geologically, the aquifer is part of what is known as the Yarragadee Formation, which is a relatively thick geological unit in the Perth Basin
. Formed during the Jurassic
Period, the Yarragadee Formation is composed primarily of non-marine fluviatile feldspathic, poorly sorted sandstones which are porous and poorly cemented, hence allowing for considerable groundwater reserves. It grades from a shale-siltstone dominated base to a cleaner sandstone in the upper portions of the formation, probably representing increased subsidence or filling of the basin during the late Jurassic.
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
located in the south west of Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
and predominantly beneath the Swan Coastal Plain
Swan Coastal Plain
The Swan Coastal Plain in Western Australia is the geographic feature which contains the Swan River as it travels west to the Indian Ocean. The coastal plain continues well beyond the boundaries of the Swan River and its tributaries, as a geological and biological zone, one of Western Australia's...
west of the Darling Scarp
Darling Scarp
The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north-south to the east of the Swan Coastal Plain and Perth, Western Australia...
. It has a north-south range from about Geraldton
Geraldton, Western Australia
Geraldton is a city and port in Western Australia located north of Perth in the Mid West region. Geraldton has an estimated population at June 2010 of 36,958...
to the south coast, but with a split in the formation south of Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
. The southern part is known as the South West Yarragadee Aquifer.
The aquifer is quite deep, situated hundreds of metres below ground level and with a thickness ranging up to about two kilometres.
In the Perth area, the Yarragadee Aquifer is located beneath the Leederville Aquifer, which itself is located beneath two superficial aquifers known as the Gnangara Mound
Gnangara Mound
The Gnangara Mound is an area north of Perth, Western Australia where a large mound of sandy soil reaches an elevation of about 60 metres. It stores about 20 cubic kilometres of fresh water, about one hundred times Perth's current annual water usage. It is currently the single most important source...
and Jandakot Mound
Jandakot Mound
The Jandakot Mound, or Jandakot Groundwater Mound, is an unconfined aquifer in south-western Western Australia. It is the smaller of the two main shallow aquifers near Perth that together supply about 40% of Perth's drinking water. Its highest point lies about 18 km south of Perth’s central...
. These aquifers are separated by impervious layers with no groundwater called aquitards.
The Yarragadee Aquifer stores about 1000 cubic kilometres of water, compared to about 20 cubic kilometres in the Gnangara Mound. As such it is seen as a potential source of water, and the Water Corporation
Water Corporation
-Overview:The Water Corporation is the principal supplier of water, wastewater and drainage services throughout the state of Western Australia...
of Western Australia currently extracts about 45 gigalitres
Litre
pic|200px|right|thumb|One litre is equivalent to this cubeEach side is 10 cm1 litre water = 1 kilogram water The litre is a metric system unit of volume equal to 1 cubic decimetre , to 1,000 cubic centimetres , and to 1/1,000 cubic metre...
per year from the aquifer. One cubic kilometre is equivalent to 1000 GL.
Ultimately the Yaragadee Aquifer is replenished by rainfall. This recharging is usually where there are outcroppings near other aquifers like the Leederville Aquifer. There are also outcrops near the surface in the vicinity of the Blackwood River
Blackwood River
The Blackwood River is a major river and catchment in the South West of Western Australia.The river begins at the junction of Arthur River and Balgarup River near Quelarup and travels in a south westerly direction through the town of Bridgetown then through Nannup until it discharges into the...
. Current models estimate this recharge at about 280 to 340 GL per year. This groundwater can remain in the aquifer for many years; in some areas the age of the groundwater is over 30,000 years.
Geologically, the aquifer is part of what is known as the Yarragadee Formation, which is a relatively thick geological unit in the Perth Basin
Perth basin
The Perth Basin is a thick sedimentary basin in Western Australia. It lies beneath the Swan Coastal Plain west of the Darling Scarp, representing the western limit of the much older Yilgarn Craton, and extends further west offshore...
. Formed during the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
Period, the Yarragadee Formation is composed primarily of non-marine fluviatile feldspathic, poorly sorted sandstones which are porous and poorly cemented, hence allowing for considerable groundwater reserves. It grades from a shale-siltstone dominated base to a cleaner sandstone in the upper portions of the formation, probably representing increased subsidence or filling of the basin during the late Jurassic.