TheNepean River[needs IPA] (Darug:Yandhai[1]), is amajor perennial river, located in the south-west and west ofSydney,New South Wales, Australia. The Nepean River, and, continuing by its downstream name, theHawkesbury River, almost encircles the metropolitan region of Sydney.
The headwaters of the Nepean River rise nearRobertson, about 100 kilometres (62 mi) south of Sydney and about 15 kilometres (9.3 mi) from theTasman Sea. The river flows north in an unpopulated water catchment area intoNepean Reservoir, which suppliespotable water for Sydney. North of the dam, the river forms the western edge of Sydney, flowing past the town ofCamden and the city ofPenrith, south of which flowing through theNepean Gorge. NearWallacia it is joined by thedammedWarragamba River; and north of Penrith, nearYarramundi, at itsconfluence with theGrose River, the Nepean becomes the Hawkesbury River.
The river supplies water to Sydney's five million people as well as supplying agricultural production. This, combined with increased pressures from land use change for urban development, means the river has been suffering significant stress.[citation needed]
There are eleven weirs located on the Nepean River that significantly regulate its natural flow. The river has been segmented into a series of weir lakes rather than a freely flowing river and is also impacted by dams in the Upper Nepean catchment.[3]
The Wallacia Weir was initially built as a wooden weir for theJohn Blaxlandflour mill at Grove Farm. The first Australian fishsteps were built when the current concrete weir was built at the beginning of the Nepean Gorge, an anticendant entrenched meander caused by the slow uplift during theBlue Mountainsorogeny carved down through the fifty-million-year-oldHawkesbury sandstone.
In the 1950s, the building of theWarragamba Dam across the steep gorge of theWarragamba River, the Nepean's major tributary, intercepted the flow of the great bulk of its waters and diverted them to meet the needs of the growing Sydney metropolitan area, reducing the river to a shadow of its former self.[4]
These dams and weirs have had a potent effect, blocking migratory native fish likeAustralian bass (also locally commonly known as perch) from much of their former habitat, and reducing floods and freshets needed for spawning. Nevertheless, the Hawkesbury/Nepean remains an important and popular wild bass fishery.
The luscious banks of the Nepean River provide a natural haven for local flora and fauna and a quiet location for local residents to relax. AtEmu Plains, the western bank of the river provides a location for outdoor theatre productions on warm summer nights. The eastern bank at Penrith providesbarbecue facilities and children's play equipment, as well as a wide pathway running for several kilometres for strolls along the riverbank. The eastern bank is also the home of the Nepean Rowing Club.
Wallacia Mandi, aMandaeansmandi (temple) inWallacia, is located on the west bank of the Nepean River. Water from the Nepean River is pumped into baptismal pools at the mandi forritual purification.[5][6][7]
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Aboriginal people used the river regularly, and their fish traps could be seen atYarramundi before sand and gravel mining redirected the river.Charles Darwin also wrote of people atEmu Ford, commenting on their skill with spears, whileWatkin Tench of theRoyal Marines also noted their use of spears, lines and nets to capture fish. The people of the Nepean region also regularly traded with people of the western plains via a route that Bell followed when he laid down an alternate route over the mountains, now calledBells Line of Road.
Near Penrith, since 1971 numerous Aboriginal stone tools were found in Cranebrook Terraces gravel sediments deposited by the Nepean River 40,000 to 50,000 years ago, according to repeated, revised and corroboratedradiocarbon andthermoluminescence dating. At first when these results were new they were controversial. More recently in 1987 and 2003 dating of the same sediments strata has revised and corroborated these dates.[8][9] A great many more artefacts made by people have been found in the region dating back to within the last 5,000 years. Karskens et al. have made an attempt to recover, integrate and map archaeological data of the area from both published and unpublished reports.[10][11]
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When theBritish colony was established at Sydney in 1788, the Governor, Captain Arthur Phillip, charted the coast 50 km north to the mouth of the Hawkesbury and around 32 km upstream till they were stopped by a waterfall, most likely at Hawkesbury Heights.[12] Phillip named the river after Lord Hawkesbury, later titledCharles Jenkinson, 1st Earl of Liverpool, President of the Privy Council Standing Committee on Trade.
Meanwhile, LieutenantWatkin Tench set off to walk inland, west of Sydney. About 60 kilometres (37 mi) inland, at the foot of theBlue Mountains, he discovered a large river which he named Nepean afterEvan Nepean, the Under Secretary of State at the Home Office and a close personal friend of Arthur Phillip.[13] It took about three years to realise that the Nepean flowed into the Hawkesbury.
Nepean river was also one of the pivotal sites of theHawkesbury and Nepean Wars, fought between theKingdom of Great Britain and local aboriginal clans in the late 1700s and early 1800s.[14]
During the 1820s, the Nepean district's most famous early settler, the landowner and physician SirJohn Jamison (1776–1844), erected aGeorgian mansion, calledRegentville House, on the model estate which he had established on a rise overlooking the river, not far from the present-day city ofPenrith. Jamison is considered one of early Australia's most important political and agricultural pioneers. A fire devastated the house in the 1860s.
Despite forming the effective western and south-western boundary of the metropolitan region of Sydney for its entire length, there are very few fixed crossings of the Nepean River. Going upstream, these comprise:
| Crossing name (Unofficial name) | Right bank crossing location | Left bank crossing location | Comments/use | Image |
|---|---|---|---|---|
| Yarramundi Bridge | Yarramundi | Agnes Banks | Carries theSpringwood Road | |
| Victoria Railway Bridge | Emu Plains | Penrith | Completed in 1907, the bridge carries the electrified and duplicatedMain Western railway line. |  |
| Victoria Bridge | Completed in 1867 and listed on theNSW State Heritage Register, the bridge initially carriedrail andhorse-drawn vehicles, and now theGreat Western Highway, with a daily traffic volume of approximately 24,500 vehicles in 2009.[15] |  | ||
| Yandhai Nepean Crossing | Completed in 2018, the bridge carries pedestrian and cycle traffic. | |||
| Regentville Bridge | Leonay | Regentville | M4 Motorway, and in 2011, carried an average of 55,000 vehicles per day[15] | |
| Wallacia | Carries the Silverdale Road | |||
| Brownlow Hill | Carries the Cobbitty Road | |||
| Camden | Kirkham | Carries the Macquarie Grove Road, located adjacent to theCamden Airport | ||
| Cowpasture Bridge | Elderslie | Carries road traffic on the Camden-Narellan Road | ||
| Macarthur Bridge | Spring Farm | Opened in 1973, this bridge is 1.12 kilometres (0.70 mi) long and carries theCamden Bypass. |  | |
| Menangle | Menangle Park | Carries road traffic on the Menangle Road | ||
| Menangle Railway Bridge | Built in 1864 under the direction ofJohn Whitton, this is the oldest surviving rail bridge in New South Wales; and carries theMain Southern railway line |  | ||
| Menangle | Carries road traffic on theHume Highway | |||
| Douglas Park Bridge | Douglas Park | A pair of concrete bridges that carry road traffic on theHume Highway |  | |
| Carries road traffic on the Douglas Park Drive. | ||||
| Maldon Bridge | Maldon | Completed in 1980, the concrete beam bridge carries thePicton Road. | ||
| Maldon Suspension Bridge | Completed in 1903 and listed on theNSW State Heritage Register, the woodensuspension bridge carried road traffic, and is now closed to all traffic |  | ||
| Pheasants Nest Bridge | Pheasants Nest | Carries road traffic on theHume Highway | ||
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The first flood on record - apparently a small occurrence - was in 1795. Others followed in 1799, March & October 1806[16] and 1809. In 1810, after a series of major floods on the Hawkesbury,Governor Macquarie proclaimed the ‘Macquarie Towns’ ofWindsor, Richmond,Wilberforce,Castlereagh, andPitt Town in an attempt to ensure that development was restricted to higher ground, free of flooding. The devastation caused by flooding in February 1817 promptedGovernor Macquarie to issue a notice exhorting settlers, in the strongest possible terms, to build their residences above the established flood levels.[17]
More flooding occurred in 1857 and twice in 1860, both February and May.[18]
The most devastating flood occurred in June 1867 with the Nepean River estimated to have reached 13.4 metres (44 ft) in the river, and 27.47 metres (90.1 ft)AHD. This flood carried away the approaches to the recently builtVictoria Bridge. Emu Plains, Castlereagh, and the lower parts of Penrith were all under flood, causing immense loss of property. Many houses were carried into the river by landslides. Many residents were forced to take refuge in public buildings such as the Penrith Hospital and the public schools. A major flood such as that of 1867 would cause inundation of over 16,000 dwellings and damage costing approximately A$1.4billion.[19]
There have been other notable floods since, particularly that of July 1900 and March 1914. Again there was much flooding of streets and loss of houses and property along the river.
1974 was another significantLa Niña flood event.[20]
During the2021 New South Wales floods, the Nepean River became overflowed, peaking at 10 m (32.81 ft), withWindsor Bridge submerging in its waters, leading to inundated homes and isolated animals in the surrounds.[21]
TheAustralian Mandaean community in theSydney metropolitan area regularly performsmasbuta (baptism) rituals in the Nepean River,[22] typically in and aroundWallacia Mandi.[23]
{{cite journal}}:Cite journal requires|journal= (help)Hawkesbury River region, New South Wales, Australia | |||||||||
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