The Yarragadee Aquifer is a significant freshwater

aquifer An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

located in the south west of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

and predominantly beneath the

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 geol ...

west of the

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. The escarpment extends generally north of Bindoon, to ...

. It has a north–south range from about

Geraldton Geraldton (Wajarri language, Wajarri: ''Jambinu'', Wilunyu language, Wilunyu: ''Jambinbirri'') is a coastal city in the Mid West (Western Australia), Mid West region of Western Australia, north of the state capital, Perth. As of the , Geraldt ...

to the south coast, but with a split in the formation south of

Perth Perth () is the list of Australian capital cities, capital city of Western Australia. It is the list of cities in Australia by population, fourth-most-populous city in Australia, with a population of over 2.3 million within Greater Perth . The ...

, Western Australia. 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 The Gnangara Mound is an area north of Perth, Western Australia where a large mound of sandy soil reaches an elevation of about . It stores about of fresh water, about one hundred times Perth's current annual water usage. It is currently the si ...

and

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, Western Australia, Perth (the other being the Gnangara Mound, north o ...

. These aquifers are separated by impervious layers with no groundwater, called

aquitard An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

s. 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 The litre ( Commonwealth spelling) or liter (American spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metres (m3). A cubic ...

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 The Blackwood River is a major river and catchment in the South West (Western Australia), South West of Western Australia. Course The river begins at the junction of Arthur River (Western Australia), Arthur River and Balgarup River near Que ...

. 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 The Perth Basin is a thick, elongated 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 The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

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. The Dalkeith Hot Pool was formed by water from the Yarragadee Aquifer.

References

* * * * * * * {{Aquifers Aquifers in Australia Swan Coastal Plain