| River Derwent | |
|---|---|
 Sunrise over the River Derwent | |
  Location of theriver mouth inTasmania | |
| Native name | timtumili minanya (Mouheneenner language) |
| Location | |
| Country | Australia |
| State | Tasmania |
| Cities | Derwent Bridge,New Norfolk,Hobart |
| Physical characteristics | |
| Source | Lake St Clair |
| • location | Central Highlands |
| Source confluence |
|
| • location | Cradle Mountain-Lake St Clair National Park |
| • coordinates | 42°7′12″S146°12′37″E / 42.12000°S 146.21028°E /-42.12000; 146.21028 |
| • elevation | 738 m (2,421 ft) |
| Mouth | Storm Bay |
• location | Hobart |
• coordinates | 43°3′3″S147°22′38″E / 43.05083°S 147.37722°E /-43.05083; 147.37722 |
• elevation | 0 m (0 ft) |
| Length | 239 km (149 mi) |
| Basin size | 9,832 km2 (3,796 sq mi) |
| Discharge | |
| • location | Storm Bay |
| • average | 90 m3/s (3,200 cu ft/s) |
| • minimum | 50 m3/s (1,800 cu ft/s) |
| • maximum | 140 m3/s (4,900 cu ft/s) |
| Basin features | |
| Tributaries | |
| • left | Nive River,Dee River,River Ouse,Clyde River,Jordan River |
| • right | Repulse River, Tyenna River,Styx River,Plenty River,Lachlan River |
| Naturallakes | Saint Clair Lagoon;Lake St Clair |
| [1][2] | |
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TheRiver Derwent, also known astimtumili minanya inpalawa kani,[3] is a significant river andtidalestuary inTasmania, Australia. It begins its journey as afreshwater river in theCentral Highlands atLake St Clair, descending over 700 metres (2,300 ft) across a distance of more than 200 kilometres (120 mi). At the settlement ofNew Norfolk in theDerwent Valley its waters becomebrackish, flowing throughHobart, the capital city of Tasmania, itsseawater estuary eventually empties intoStorm Bay and theTasman Sea.
Historically, the banks of the Derwent were covered by forests and frequented byAboriginal Tasmanians. With the arrival of European settlers, the area saw agricultural development and the construction of dams for hydro-electricity generation during the 20th century.
Today, the Derwent's catchment area is characterised byagriculture,forestry, andhydropower generation. It serves as a vital source of water for irrigation and urban supply, notably providing a significant portion of Hobart's water needs.[4] The river is also crucial for recreation, supporting activities such as boating, fishing, and leisure along its banks. Additionally, it facilitates marine transportation and various industrial activities, playing a central role in Tasmania's economy and lifestyle.[2]
The upper part of the river was named after theRiver Derwent, Cumbria by British CommodoreJohn Hayes who explored it in 1793. The name isBrythonic Celtic for "valley thick with oaks".[5][6]
Matthew Flinders placed the name "Derwent River" on all of the river.[7]
The name "River Derwent" was officially endorsed on 20 May 1959.[8]
The River Derwent valley was inhabited by theMuwinina people for at least 8,000 years before British settlement.[9] Evidence of their occupation is found in many middens along the banks of the river.[citation needed] The first European to chart the river wasBruni d'Entrecasteaux, who named it theRivière du Nord in 1793.[10] Later that same year,John Hayes explored the river and named it after theRiver Derwent, which runs past his birthplace ofBridekirk,Cumberland.[11]
When first explored by Europeans, the lower parts of the valley were clad in thickshe-oak forests, remnants of which remain in various parts of the lower foreshore.[12]
There was a thriving whaling industry until the 1840s when the industry rapidly declined due to over-exploitation.[13]
Formed by the confluence of the Narcissus and Cuvier rivers withinLake St Clair, the Derwent flows generally southeast over a distance of 187 kilometres (116 mi) toNew Norfolk and the estuary portion extends a further 52 kilometres (32 mi) out to the Tasman Sea. Flows average in range from 50 to 140 cubic metres per second (1,800 to 4,900 cu ft/s) and the mean annual flow is 90 cubic metres per second (3,200 cu ft/s).[12]
The largeestuary forms thePort of the City ofHobart – the deepest shelteredharbour in theSouthern Hemisphere.[14] Some past guests of the port includeHMS Beagle in February 1836, carryingCharles Darwin; theUSS Enterprise;USS John C. Stennis andUSS Missouri. The largest vessel to ever travel the Derwent is the 113,000-tonne (111,000-long-ton), 61-metre (200 ft) high, ocean linerDiamond Princess, which made her first visit in January 2006.[15]
At points in its lower reaches the river is nearly 3 kilometres (1.9 mi) wide, and as such is the widest river in Tasmania.[citation needed]
The Derwent estuary contains dozens of white sandy beaches, many of which are staples of local activity within Hobart suburbs and includeBellerive Beach,Blackmans Bay Beach,Howrah Beach,Nutgrove Beach,Lords Beach,Long Beach,Taroona Beach,Hinsby Beach,Kingston Beach and Windermere Beach.
Until the construction of severalhydro-electric dams between 1934 and 1968, the river was prone to flooding.[citation needed] Now there are more than twenty dams and reservoirs used for the generation of hydro-electricity on the Derwent and its tributaries, including theClyde,Dee,Jordan,Nive,Ouse,Plenty andStyx rivers. Seven lakes have been formed by damming the Derwent and the Nive rivers for hydroelectric purposes and include the Meadowbank, Cluny, Repulse, Catagunya, Wayatinah, Liapootah and King William lakes or lagoons.
The Upper Derwent is affected by agricultural run-off, particularly from land clearing and forestry. The Lower Derwent suffers from high levels oftoxic heavy metal contamination in sediments. TheTasmanian Government-backedDerwent Estuary Program has commented that the levels ofmercury,lead,zinc andcadmium in the river exceed national guidelines. In 2015 the program recommended against consuming shellfish and cautioned against consuming fish in general. Nutrient levels in the Derwent between 2010 and 2015 increased in the upper estuary (between Bridgewater and New Norfolk) where there had beenalgal blooms.[12]
A large proportion of toxic heavy metal contamination stems fromlegacy pollution caused by major industries that discharge into the river including theRisdon Zinc Works, a historic smelter establish atLutana in 1916,[16] and theBoyer Mill atBoyer which opened in 1941.[17][18][19][20]
The Derwent adjoins or flows through thePittwater–Orielton Lagoon,Interlaken Lakeside Reserve and Goulds Lagoon, allwetlands of significance protected under theRamsar Convention.[2]
In recent years,southern right whales finally started making appearance in the river during months in winter and spring when their migration takes place. Some females even started using calm waters of the river as a safe ground for giving birth to their calves and would stay over following weeks after disappearance of almost 200 years due to being wiped out by intense whaling activities. In the winter months of 2014,humpback whales and aminke whale (being the first confirmed record of this species in the river) have been recorded feeding in the River Derwent for the first time since the whaling days of the 1800s.[21]
The rarespotted handfish (Brachionichthys hirsutus), whose only habitat is in the Derwent estuary and surrounds,[22] was the first marine fish to be listed ascritically endangered in theIUCN Red List, in 1996.[23][24] The fish is threatened by theNorthern Pacific seastar's invasion into southern Australian waters. TheNorthern Pacific seastar (Asterias amurensis), now firmly established in the Derwent,[25][26] preys on not only the fish eggs,[22] but also on the sea squirts (ascidians)[25] that help to form thesubstrate that the fish spawn on.[27]
Several bridges connect the western shore (the more heavily populated side of the river) to the eastern shore of Hobart – in the greater Hobart area, these include the five laneTasman Bridge, near the CBD, just north of the port; the four laneBowen Bridge; and the four laneBridgewater Bridge. Until 1964 the Derwent was crossed by the uniqueHobart Bridge, a floating concrete structure just upstream from where the Tasman Bridge now stands.[28]
Travelling further north from the Bridgewater crossing, the next crossing point is theBlair Street Bridge atNew Norfolk, slightly north of the point where the Derwent reverts fromseawater tofresh water,Bushy Park, UpperMeadowbank Lake, Lake Repulse Road,Wayatinah, and the most northerly crossing is atDerwent Bridge, before the river reaches its source ofLake St Clair. At the Derwent Bridge crossing, the flow of the river is generally narrow enough to be stepped across.
The river is the subject of the multimedia performance "Falling Mountain" (2005 Mountain Festival), a reference to the mountain in theCradle Mountain-Lake St Clair National Park from which the river rises.
The Derwent is mentioned in the song,Mt Wellington Reverie by Australian band,Augie March.[29] Hobart is located in the foothills ofMount Wellington.
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