TheRiver Shannon (Irish:an tSionainn, Abhainn na Sionainne or archaican tSionna[1]) is the major river on the island ofIreland, and at 360 km (224 miles) in length,[2] is the longestriver in theBritish Isles.[3][4] It drains theShannon River Basin, which has an area of 16,900 km2 (6,525 sq mi),[5] – approximately one fifth of the area of Ireland.
By tradition the Shannon is said to rise in theShannon Pot, a small pool in the townland ofDerrylahan on the slopes ofCuilcagh Mountain inCounty Cavan,Republic of Ireland, from where the young river appears as a small trout stream. Surveys have defined a 12.8 km2 (4.9 sq mi) immediate pot catchment area covering the slopes of Cuilcagh. This area includes Garvah Lough, Cavan, 2.2 km (1.4 mi) to the northeast, drained byPollnaowen.[n 1] Further sinks that source the pot include Pollboy and, throughShannon Cave, Pollahune in Cavan and Polltullyard and Tullynakeeragh inCounty Fermanagh,Northern Ireland. The highest point in the catchment is a spring at Tiltinbane on the western end of the Cuilcagh mountain ridge.[8]
From the Shannon Pot, the river subsumes a number of tributaries before replenishingLough Allen at its head.[9] The river runs through or between 11 of Ireland'scounties, subsuming the tributary riversBoyle,Inny,Suck,Mulkear andBrosna, among others, before reaching the Shannon Estuary atLimerick.
TheShannon Pot, the traditional source of the river
Many different values have been given for the length of the Shannon. A traditional value is 390 km (240 mi).[10] An official Irish source gives a total length of 360.5 km (224.0 mi) (being 258.1 km [160.4 mi] fresh and 102.1 km [63.4 mi] tidal).[6] Some Irish guides now give 344 km (214 mi).[11][12][13] Some academic sources give 280 km (170 mi),[14] although most will refuse to give a number. The reason is that there is no particular end to a river that empties into an estuary. The 344 km length relates to the distance between Shannon Pot and a line betweenKerry Head andLoop Head, the furthest reaches of the land. (It also assumes the current shipping route via Ardnacrusha, which takes 7 km (4.3 mi) off the distance.) The 280 km distance finishes where the Shannon estuary joins the estuary of theRiver Fergus, close toShannon Airport. Longer claimed lengths emerged before the use of modern surveying instruments.
At a total length of 360.5 km (224 miles), it is the longest river in Ireland.[13] That the Shannon is the longest river in the British Isles was evidently known in the 12th century, although a map of the time showed this river as flowing out of the south of Ireland.[3]
There are some tributaries within theShannon River Basin which have headwaters that are further in length (from source to mouth) than theShannon Pot source's length of 360.5 km (224 miles), such as theOwenmore River, total length 372 km (231 mi) in County Cavan[15] and theBoyle River, total length 392.1 km (243.6 mi) with its source inCounty Mayo.[16]
Upper Shannon catchment (with Shannon source, Owenmore River and Boyle River Basin)
The River Shannon is a traditional freshwater river for about 45% of its total length. Excluding the 102 km (63+1⁄2 mi) tidal estuary from its total length of 360 km (224 mi), if one also excludes the lakes (L. Derg 39 km (24 mi),L. Ree 29 km (18 mi),L. Allen 11 km (7 mi)[17] plusL. Boderg,L. Bofin,L. Forbes,L. Corry) from the Shannon's freshwater flow of258 km (160+1⁄2 mi), the Shannon, as a freshwater river, is only about 161 km (100 mi) long.
Apart from being Ireland's longest river, the Shannon is also, by far, Ireland's largest river byflow. It has a long-term average flow rate of 208.1 m3/s (7,350 cu ft/s) (atLimerick). This is double the flow rate of Ireland's second highest-volume river, the shortRiver Corrib (104.8 m3/s [3,700 cu ft/s].[18] If the discharges from all of the rivers and streams into the Shannon Estuary (including the riversFeale 34.6 m3/s [1,220 cu ft/s],Maigue 15.6 m3/s [550 cu ft/s],Fergus 25.7 m3/s [910 cu ft/s], andDeel 7.4 m3/s [260 cu ft/s])[19][20] are added to the discharge at Limerick, the total discharge of the River Shannon at its mouth at Loop Head reaches 300 m3/s (11,000 cu ft/s). Indeed, the Shannon is a major river by the time it leavesLough Ree with an average flow rate (atAthlone weir) of 98 m3/s (3,500 cu ft/s),[21] larger than any of the other Irish rivers' total flow (apart from theRiver Corrib atGalway).
The main flow of the river is affected by somedistributaries along its course, many of which rejoin it downstream. TheAbbey River flows around the northeastern, eastern, and southern shores ofKing's Island,Limerick before rejoining the Shannon atHellsgate Island.[22][23]
The river began flowing along its present course after the end of thelast glacial period.
Ptolemy'sGeography (2nd century AD) described a river called Σηνος (Sēnos) from PIE *sai-/sei- 'to bind', the root of Englishsinew and Irishsin ‘collar’, referring to the long and sinuousestuary leading up to Limerick.[24][25]
Vikings settled in the region in the 10th century and used the river to raid the rich monasteries deep inland. In 937 the Limerick Vikings clashed with those ofDublin on Lough Ree and were defeated.
In the 17th century, the Shannon was of major strategic importance in military campaigns in Ireland, as it formed a physical boundary between the east and west of the country. In theIrish Confederate Wars of 1641–53, the Irish retreated behind the Shannon in 1650 and held out for two further years againstEnglish Parliamentarian forces. In preparing aland settlement, orplantation after hisconquest of IrelandOliver Cromwell reputedly said the remaining Irish landowners would go to "Hell or Connacht", referring to their choice offorced migration west across the river Shannon, or death, thus freeing up the eastern landholdings for the incoming English settlers.
As late as 1916, the leaders of theEaster Rising planned to have their forces in the west "hold the line of the Shannon". However, in the event, the rebels were neither well enough armed nor equipped to attempt such an ambitious policy.
Though the Shannon has always been important for navigation in Ireland, there is a fall of only 18 m (59 ft) in its first 250 km (160 mi). Consequently, it has always been shallow, with 0.5 m (1 ft 8 in) depths in various places. The first serious attempt to improve navigability came in 1755 when theCommissioners of Inland Navigation orderedThomas Omer, a new immigrant from England, possibly of Dutch origin, to commence work.[26] He worked at four places betweenLough Derg andLough Ree where natural navigation was obstructed, by installing lateral canals and eitherpound locks orflash locks. He then continued north of Lough Ree and made several similar improvements, most notably by creating the firstJamestown Canal which cut out a loop of the river betweenJamestown andDrumsna, as well as lateral canals atRoosky andLanesborough.[26]
The lower Shannon betweenKillaloe andLimerick had a topography quite different from the long upper reaches. Here the river falls by 30 m (98 ft) in only 20 km (12 mi). William Ockenden, also from England, was placed in charge of works on this stretch in 1757 and spent £12,000 over the next four years, without fully completing the task. In 1771 parliament handed over responsibility to theLimerick Navigation Company, with a grant of £6,000 to add to their subscriptions of £10,000. A lateral canal, 8 km (5 mi) long with six locks, was started but the company needed more funds to complete it. In 1791,William Chapman was brought in to advise and discovered a sorry state of affairs – all the locks had been built to different dimensions and he spent the next three years supervising the rebuilding of most of them. The navigation was finally opened in 1799, when over 1,000 long tons (1,000 tonnes) of corn came down to Limerick, as well asslates andturf. But even then, there were notow paths in the river sections and there were still shoals in the summer months, as well as a lack of harbour facilities at Limerick, and boats were limited to 15–20 long tons (15–20 tonnes) load, often less.[citation needed]
With the approaching opening of theGrand Canal, the Grand Canal Company obtained permission from theDirectors General of Inland Navigation, and askedJohn Brownrigg to do a survey which found that much of Omer's work had deteriorated badly, so they started repairs. After protracted negotiations on costs and conditions, the work was completed by 1810, so that boats drawing 1.75 m (5 ft 9 in) could pass fromAthlone toKillaloe. Improvements on the lower levels were also undertaken, being completed by 1814.[citation needed]
When theRoyal Canal was completed in 1817 there was pressure to improve the navigation above Lough Ree. The Jamestown Canal was repaired, harbours built andJohn Killaly designed a canal alongside the river fromBattlebridge toLough Allen, which was opened in 1820.[citation needed]
An Act for the improvement of the Shannon Navigation from the City of Limerick to Killaloe, by rebuilding the Bridge called Baal's Bridge, in the said City.
An Act to provide for the Repayment of Sums due by the County of the City of Limerick for Advances of public Money for the Improvement of the Navigation of the River Shannon.
In the latter part of the 1820s, trade increased dramatically with the arrival of paddle-wheeledsteamers on the river which carried passengers and goods. By 1831 14,600 passengers and 36,000 long tons (37,000 tonnes) of freight were being carried. This put new pressure on the navigation and a commission was set up resulting in theShannon Navigation Improvement Act 1835 (5 & 6 Will. 4. c. 67) appointing five commissioners for the improvement of navigation and drainage who took possession of the whole navigation. Over the next 15 years, many improvements were made but in 1849 a railway was opened from Dublin to Limerick and the number of passengers fell dramatically. Freight, which had risen to over 100,000 long tons (100,000 tonnes) per year, was also halved.
But the work the commissioners carried out failed to solve the problems of flooding and there were disastrous floods in the early 1860s. Given the flat nature of most of the riverbank, this was not easily addressed and nothing much was done until the 20th century.
One of the first projects of theIrish Free State in the 1920s was theShannon hydroelectric scheme which established the Ardnacrushapower station on the lower Shannon above Limerick. The old Killaloe to Limerick canal with its five locks was abandoned and the head race constructed from Lough Derg also served for navigation. A double lock was provided at the dam.
In the 1950s traffic began to fall and low fixed bridges would have replaced opening bridges but for the actions of theInland Waterways Association of Ireland which persuaded theTánaiste to encourage passenger launches, which kept the bridges high enough for navigation. Since then the leisure trade has steadily increased, becoming a great success story.
Ballinasloe is linked to the Shannon via theRiver Suck and canal, whileBoyle is connected via the Boyle canal, theriver Boyle andLough Key. There is also the Ardnacrusha canal connected with the Ardnacrusha dam south of Lough Derg. Near Limerick, a short canal connectsPlassey with theAbbey River, allowing boats to bypass the Curraghower Falls, a major obstacle to navigation.Lecarrow village inCounty Roscommon is connected to Lough Ree via the Lecarrow canal.Jamestown Canal and theAlbert Lock form a link between the River Shannon, from south ofJamestown, to Lough Nanoge to the south ofDrumsna.
An illustration, titled "Sinend and Connla's Well", fromMyths and Legends; the Celtic Race (1910) byT. W. Rolleston
According toIrish mythology, the river was named after a woman (in many sources a member of theTuatha de Danaan) named Sionann (older spelling forms: Sínann or Sínand), the granddaughter ofManannán mac Lir.[27] She went toConnla's Well to find wisdom, despite having been warned not to approach it. In some sources she, likeFionn mac Cumhaill, caught and ate theSalmon of Wisdom who swam there, becoming the wisest being on Earth, in others, she merely drank from the well. At any rate, the waters of the well are said to have burst forth, drowning Sionann, and carrying her out to sea.[28] Notably, a similar tale is told ofBoann and theRiver Boyne. It is said that Sionann thus became the goddess of the river. Patricia Monaghan notes that "The drowning of a goddess in a river is common in Irish mythology and typically represents the dissolving of her divine power into the water, which then gives life to the land".[29]
A small myth about Sionann tells that the legendary hunter-warriorFionn mac Cumhaill was attacked by a number of other warriors at Ballyleague, near north Lough Ree. It is said that when Fionn was near to defeat, Sionnan rescued him, and he arrived with the Stone of Sionann, threw the stone, and the warriors were immediately killed. It further says that Fionn was afraid of the power of the stone and threw it into the river, where it remains at a lowford, and that if a woman named Be Thuinne finds it, then the world's end is near.[28]
The Shannon reputedly hosts a river monster named Cata, the first known mention being in the medievalBook of Lismore. In this manuscript, we are told thatSenán, patron saint ofCounty Clare, defeated the monster atInis Cathaigh.[30] Cata is described as a large creature with a horse's mane, gleaming eyes, thick feet, nails of iron, and a whale's tail.[31] Another story has anoilliphéist flee its home in the Shannon, upon hearing thatSaint Patrick has arrived to remove its kind from Ireland.[32]
Shipping in the Shannon estuary was developed extensively during the 1980s, with overIR£2 billion (€2.5 billion) investment. A tanker terminal atFoynes and an oil jetty atShannon Airport were built. In 1982 a large-scalealumina extraction plant was built atAughinish. 60,000-tonne cargo vessels now carry rawbauxite from West African mines to the plant, where it is refined to alumina. This is then exported to Canada where it is further refined to aluminium. 1985 saw the opening of a 915 MW coal-fired electricity plant atMoneypoint, fed by regular visits by 150,000-tonne bulk carriers.
A trap and transport scheme is in force on the Shannon as part of aneel management programme following the discovery of a reduced eel population. This scheme ensures safe passage for young eels betweenLough Derg and the Shannon estuary.[33][34]
Though the Shannon estuary fishing industry is now depleted, at one time it employed hundreds of men along its length. AtLimerick, fishermen based on Clancy's Strand used theGandelow to catchSalmon.[35] The Abbey Fishermen used a net and a boat type known as a Breacaun to fish between Limerick City and Plassey until 1929.[36] In 1929, the construction of a dam atArdnacrusha severely impacted salmon breeding and that, and the introduction of quotas, had by the 1950s caused salmon fishing to cease.[37] However, recreational fishing still goes on. Further down theShannon Estuary atKilrush theCurrach was used to catchherring as well as drift netting for salmon.
Dublin City Council published a plan in 2011 to supply up to 350 million litres of water a day from Lough Derg to Dublin city and region. In 2016 theParteen Basin to the south of lough was chosen as the proposed site of extraction. Water would be pumped to a break pressure tankKnockanacree nearCloughjordan in County Tipperary and gravity fed from there bypipeline to Dublin.[38][39][40][41]
^abFeeley, Hugh B.; Bruen, Michael; Bullock, Craig; Christie, Mike; Kelly, Fiona; Kelly-Quinn, Mary (2017).ESManage Project: Irish Freshwater Resources and Assessment of Ecosystem Services Provision. Vol. Report No. 207. EPA. pp. Section 3.1.2.ISBN978-1-84095-699-3.
^Dobrzynski, Jan (2016)."Introduction".River Severn: From Source to Sea. Amberley Publishing.ISBN9781445649054. Retrieved4 January 2023.
^"Chapter 2: Study Area"(PDF).Biology and Management of European Eel (Anguilla anguilla, L) in the Shannon Estuary, Ireland.Archived(PDF) from the original on 7 September 2014. Retrieved7 September 2014.
^Simms, J.G. (1986).War and Politics in Ireland, 1649-1730. London: Hambledon Press. p. 22.ISBN978-0907628729. Retrieved23 October 2013.The Shannon divides at Limerick; a branch, called the Abbey river, makes an island which was called the King's Island.
^"Abbey River, Ireland".Geographical Names. National Geospatial-Intelligence Agency, Bethesda, Maryland, US. 5 May 1998.Archived from the original on 29 October 2013. Retrieved23 October 2013.
^"Ireland"(PDF).romaneranames.uk. Archived fromthe original(PDF) on 2 April 2019. Retrieved3 January 2020.
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