Nambung River
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The Nambung River is a river in the Wheatbelt region of
Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...
, north of
Perth Perth is the capital and largest city of the Australian state of Western Australia. It is the fourth most populous city in Australia and Oceania, with a population of 2.1 million (80% of the state) living in Greater Perth in 2020. Perth is ...
. The river drains an area between the towns of Cervantes and Badgingarra. In its lower reaches the Nambung River forms a chain of waterholes in the Nambung
Wetlands A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...
where it disappears underground into a
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...
system from the
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
.


History

The Nambung River was encountered by explorer
George Grey Sir George Grey, KCB (14 April 1812 – 19 September 1898) was a British soldier, explorer, colonial administrator and writer. He served in a succession of governing positions: Governor of South Australia, twice Governor of New Zealand, Go ...
on 16 April 1839, during his second disastrous expedition along the Western Australian coast. He named it the Smith River after Frederick Smith, a member of his party who died from exhaustion during the final days of the expedition. Smith was the 18-year-old grandson of William Smith, prominent M.P. for
Norwich Norwich () is a cathedral city and district of Norfolk, England, of which it is the county town. Norwich is by the River Wensum, about north-east of London, north of Ipswich and east of Peterborough. As the seat of the See of Norwich, with ...
, and was a first cousin to
Florence Nightingale Florence Nightingale (; 12 May 1820 – 13 August 1910) was an English Reform movement, social reformer, statistician and the founder of modern nursing. Nightingale came to prominence while serving as a manager and trainer of nurses during t ...
. It was renamed the Nambung River by government surveyor John Sherlock Brooking in 1874-75. The Nambung River's longest tributary was subsequently named Frederick Smith Creek. The river was recorded as the Namban in 1875 by Staff-Commander William Edwin Archdeacon R.N., who was in charge of the Admiralty survey of the coast of Western Australia. It was described as such in the description of the Dongara to Perth stock route in 1889. The spelling Nambung was in general use from at least 1888, the name being derived from an Aboriginal word possibly meaning ''crooked'' or ''winding''.


Geography

The Nambung River catchment area is bounded by those of the Hill River (to the north) and Mullering Brook (to the east and south). Its main tributaries are Bibby Creek, Mount Jetty Creek and Frederick Smith Creek. The total length of the Nambung River-Frederick Smith Creek system is approximately . The river terminates at the surface in limestone karst terrain 9 km south-south-east of Cervantes, from the
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
coast. The river makes a chain of waterholes before it disappears into a cave system. Water eventually seeps out along the coastline. The Pinnacles, within the Nambung National Park, lie within the southern part of the Nambung River catchment. The surrounding area is subject to the Nambung National Park Management Plan. Large areas of
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 ...
native bush land are well preserved within the lower reaches of the Nambung river system, dominantly comprising low scrub heath (less than tall).


Geohydrology

The Nambung River flows underground into a karst system bounding the eastern edge of the Nambung Wetlands, within Nambung National Park. Features associated with the wetlands include
salt lake A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per litre). ...
s, swamps, lagoons and dunal damplands. Most lagoons and lakelets in the area are isolated from the sea and from surface creek drainage, being fed by rainfall and groundwater flow from surrounding dunes and limestone. There is a complicated
hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
with examples of long lakes appearing virtually overnight and solution pipes spouting columns of water. When the backplain to the wetlands floods, waters are filtered into a karst aquifer and into the sea via underground channels. As a consequence of the percolation of surface water through the limestone substrate, the catchment boundaries of main drainage lines become undefined over the limestone topography.


Salinity and geology

The Nambung River and Wetland have variable
salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
that can be independent of surface activities.
Groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
salinity is highest at discharge boundaries formed by
salt lake A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per litre). ...
s, and in the lower catchment area of the river where there is saline groundwater discharge from 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 Mya. The J ...
''Eneabba Formation'' and '' Cattamarra Coal Measures''. The upward discharge of brackish groundwater from
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
aquifers into superficial formations causes the salinity of the groundwater in the superficial formations locally to exceed 8,000 mg/L TDS on the Nambung River flats east of Cervantes.


Karst terrain

The superficial formations and Mesozoic formations discharge large volumes of groundwater to the sea. Much of this discharge flows through karstic solution channels in the
Tamala limestone Tamala Limestone is the geological name given to the widely occurring eolianite limestone deposits on the western coastline of Western Australia, between Shark Bay in the north and nearly to Albany in the south. The rock consists of calcarenit ...
, a calcareous and siliceous formation deposited in the middle to late
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
(1,500,000-10,000 years ago). Many karst features of the ''Tamala Limestone'', the result of karst processes and include subterranean drainage through caverns and tunnels, dolines and
sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...
s, residual cone hills and circular depressions, limestone pillars and root concretions, can be linked directly to the Nambung River. Caves have evolved in relation to the movement of weakly acidic water groundwater that gradually dissolves calcium carbonate in the limestone, which can be locally redeposited within caves and cavities.


References

{{Rivers of Western Australia Rivers of the Wheatbelt region