The River Shannon (Irish: Abha na Sionainne / a tSionainn / a tSionna ) is the longest river in Ireland on 360.5 kilometers (224 miles).  It empties the Shannon River Basin has an area of 16,865 km 2 (6,512 ml 2 ),  one-fifth of the area of Ireland.
Shannon parts west of Ireland (principally the province of Connacht) from the east and south (Leinster and most of Munster). County Clare, which is west of the Shannon, but part of the province of Munster, is the major exception. The river represents a major physical barrier between East and West, with fewer than thirty-points between Limerick city in the south and the village Dowrai north.
The river is named for Sionna , a Celtic goddess. 
Shannon has been an important waterway since antiquity, having been identified by the Greek-Egyptian geographer Ptolemy. The river flows generally south from the Shannon Pot in Cava Before turning west and empties into the Atlantic Ocean, 102.1 kilometers (63.4 miles) long Shannon Estuary.  Limerick city stands at the point where river water meets the sea water of mynningen.Shannon is tidal east Limerick as far as the base of the pond Ardnacrusha. 
By tradition, Shannon said the rise in the Shannon Pot, a small pool on the slopes of Mountain Cuilcagh in Cavan, where the young river appears as a small trout stream. Research has defined a 12.8 km 2 immediate pot catchment covers the slopes of Cuilcagh. This area includes Garvah Lough, County Cavan, 2.2 km to the northeast, drained of Pollnaowen . [N 1] Further sinks source pot includes Pollboy and through Shannon Cave, Pollahune in Cavan and Poll Customs Yard and Tullynakeeragh in County Fermanagh, Northern Ireland. The highest point in the catchment is a feather in Tiltinbane on the western end of Cuilcagh mountain ridge. 
From Shannon Pot, subsumes the river a number of tributaries before filling Lough Allen in the lead.  The river runs through or between 11 of Ireland’s counties, subsuming tributary rivers Boyle, Inny, Suck, Mulkear and Brosna, among others, before reaching the Shannon Estuary at Limerick.
Many different values are given for the length of the Shannon. A traditional value is 390 km (240 mi).  An official Irish source gives a total length of 360.5 km (224.0 mi) (= 258.1 km fresh + 102.1 kilometers tides). [4 ] most Irish guides offer now 344 km (214 mi).    some academic sources provide 280 km (170 mi),  but most will refuse to give a speech. The reason is that there is no particular end to a river that flows into an estuary. The 344 km length refers to the distance between the Shannon Pot and a line between Kerry Head and Loop Head, the furthest reaches of the ground. (It also assumes the delivery road via Ardnacrusha.  ) The 280 km distant finish which joins the Shannon estuary mouth of the River Fergus near Shannon Airport. Longer distances occurred prior to the use of modern instruments.
At a total length of 360.5 kilometers (224 miles), it means that it is the longest river in Ireland.  The Shannon is the longest river in the wider British Isles was apparently known in the 12th century, although a map of time showed that river that flows into the south of Ireland. 
The River Shannon is a traditional freshwater river for about 45% of its total length. Excluding the 63.5 mil tidal estuary from its total length of 224 miles, if one also excludes lakes (L. Derg 24 miles, 18 miles L. Ree, L. Allen 7 miles plus L. Boderg, L. Bofin, L. Forbes, L. Corry) from Shannon freshwater flow of 160.5 miles, Shannon, as a freshwater river, is only about 100 miles long.
There are some tributaries within the Shannon River Basin has been spilling which is longer in length (from source to mouth) than Shannon Pot source such as Owenmore river in Cavan  and the Boyle river with its source in Mayo. 
In addition to being Ireland’s longest river, Shannon is also superior, Ireland’s largest river flow. It has a long-term average flow rate of 208.1 m 3 / s (at Limerick city). This is double the flow of Ireland’s second largest river, the River Corrib (104.8 m 3 / s).  If the emissions of all rivers and streams in the Shannon Estuary (including rivers Feale 34.6 m 3 / s, Maigue 15 6 m 3 / s, Fergus 25.7 m 3 / s, and Deel 7.4 m 3 / s)   added to discharge at Limerick, the total discharge of the river Shannon in his mouth on Loop Head reaches 300m 3 / s. In fact, the Shannon a great river by the time it leaves the Lough Ree with an average flow rate (at Athlone weir) of 98m 3 / s,  which is larger than any of the other Irish river’s total flow (apart from the river Corrib in Galway).
The Shannon Callows areas of the lowlands along the river, is classified as a special area of conservation.
Settlements along the river (go up the river) include Kilrush, Tarbert, Shannon village and dowra.
History and Folklore
The river began flowing along its present course after the end of the last ice age.
According to Irish mythology, the river was named after a woman named Sionann (older spelling: Sínann or Sínand), grandson of Lir. She went tillConnla Well to find wisdom, although warned not to approach it. In some sources she who Fionn mac Cumhaill, caught and ate salmon of wisdom who swam there, will be the wisest creature on earth. But well then burst, drowning Sionann and carry her out to sea.  A similar story is told by Boann and the River Boyne. It is believed that Sionann was the goddess of floden.Patricia Monaghan notes that “the drowning of a goddess in a river is common in Irish mythology and typically represents the dissolution of her divine power in the water, which then gives life to the earth.” 
Shannon said to host a river monster named Cata, first appears in the medieval book Lismore. In this manuscript, we hear that the tendon, the patron saint of County Clare, defeated the monster on Inis Cathaigh.  Cata described as a huge monster with a horse’s mane, shining eyes, thick feet, nails, iron and a whale tail. [25 ]
Vikings settled in the region in the 10th century and used the river to raid the rich monasteries deep inland. In 937 Limerick Vikings clashed with Dublin on Lough Ree and were defeated.
In the 17th century, Shannon was of great strategic importance for military operations in Ireland, because it formed a natural boundary between the east and west of the country. The Irish League of Wars of 1641-1653, the Irish retreated behind the Shannon in 1650, and held out for another two years against the English Parliamentarian forces. In the production of a rural population, or planting after his conquest of Ireland Oliver Cromwell is said said the remaining Irish landowners would go to “Hell or Connaught”, referring to their choice of forced migration to the west of the River Shannon, or death, thus freeing the eastern holdings for incoming English settlers.
In Williamite war in Ireland (1689-1691), the Jacobites also pulled behind Shannon after their defeat at the Battle of the Boyne in 1690. Athlone and Limerick, cities commanding bridges over the river, saw bloody sieges. (See sieges of Limerick and the Siege of Athlone).
As late as 1916, the leaders of the Easter Rising planned to have their forces in the West “hold the line in Shannon.” But in case the rebels were not well enough armed or equipped to attempt such an ambitious policy.
Shannon river is closely related to Ireland, social, cultural, military, economic and political history.
Although Shannon has always been important for navigation in Ireland, there is a reduction of only 18 m (60 ft) in the first 250 km (140 miles).Consequently, it has always been shallow with 0.5m (2 feet) deep at various locations. The first serious attempt to improve things came in 1755 when the Commissioners of Inland Navigation ordered Thomas Omer, a new, possibly Dutch immigrants from England, to begin the work.  He treated the four sites between Lough Derg and Lough Ree where natural navigation was prevented by installing side channels and either pound lock or flash locks. He then proceeded north of Lough Ree and made a number of similar improvements, mainly by creating the first Jamestown Canal that cuts out a loop of the River between Jamestown and Drumsna and side channels in Roosky and Lanesborough.
The lower Shannon between Kill and Limerick was a different story. Here the river falls 30 m (100 ft) at just 20 km (12 mi). William Ockenden, also from England, was placed in charge of this in 1757 and spent £ 12,000 during the next four years without fully completing the task. 1771 parliament handed responsibility to Limerick Navigation Company with a contribution of £ 6,000 to add to their subscriptions of £ 10,000. A lateral channel five miles long with six locks began but the company needed more to complete it. In 1791, William Chapman was sent in to provide advice and discovered a sorry state. All locks were built to different dimensions and he spent the next three years to rebuild most of them. Navigation finally opened in 1799, when over 1,000 tons of corn came down to Limerick, as well as shale and peat. But even then, there were no tow vägari river sections and there were still schools during the summer months, no port facilities at Limerick and boats limited to 15-20 tons of cargo, often less.
With the approaching opening of the Grand Canal, the Grand Canal Company received permission from the directors-general and asked John Brownrigg to do a survey that found that a large part of Omer work had deteriorated badly, so they started repairs. After protracted negotiations on the costs and conditions, it was the work of 1810, so that the boats pull 5’9 “could pass from Athlone to Kill. Improvements at the lower levels were also made, which ends with in 1814.
When Djurgarden ended in 1817, there was pressure to improve navigation of Lough Ree. The Jamestown canal was repaired, ports are being built and John Killaly designed a canal at the side of the river from Battle to Lough Allen opened 1820th
In the late 1820s, increased trade dramatically with the arrival of the paddle-wheel steamers on the river through passengers and cargo. By 1831 14.600 passengers and 36,000 tons of cargo transported. This put new pressure on navigation and a commission was set up, resulting in the Shannon Navigation Act of 1835 concerning the appointment of five commissioners to improve navigation and drainage that took possession of the entire navigation. During the next 15 years, many improvements have been made, but in 1849 a railway was opened from Dublin to Limerick and the number of passengers declined drastically. Freightliner, which had risen to over 100,000 tons per year, has also been halved.
But the work of the Commission carried out failed to solve the problems of flooding and there was disastrous flooding in the early 1860s. Given the flat nature of most of the river bank, this was not easily addressed and nothing much was done until the twentieth century.
One of the first projects in the Irish Free State in the 1920s was the Shannon hydroelectric scheme established Ardnacrusha power station on the lower Shannon above Limerick. The old Guy Limerick canal with five locks were constructed and the head race of Lough Derg are also served for navigation.A double lock was released at the dam.
In the 1950s, began to fall traffic and low fixed bridges would have replaced opening bridges, but for the actions of inland waterways Association of Ireland who persuaded Tánaiste to encourage passenger launches, held bridges high enough for navigation. Since that time trade has increased steadily, to become a great success.
There are also many canals that connects with the River Shannon. The Royal Canal and Canal connects Shannon to Dublin and the Irish Sea. It is linked to the river Erne ochLough Erne Shannon-Erne waterway. Ballinasloe is connected to Shannon via the River Suck and the canal, while Boyle is connected via Boyle canal, river Boyle and Lough Key .There is also the Ardnacrusha channel connected to Ardnacrusha dam south of Lough Derg.Near Limerick, a short channel connecting Plassey with the Abbey River, allowing ships to bypass Curraghower Falls, a major obstacle to navigation.Lecarrow village in County Roscommon is connected to Lough Ree through Lecarrow channel. Jamestown Canal and Albert Lock forms a link between the Shannon River, from south of Jamestown, Lough Nanoge south of Drumsna.
Despite the 360.5 km (224.0 mi) long, rising only 76 m (256 ft) above sea level, so the river is easily navigable, with only a few locks along its length.There are envattenvärmeanläggning at Ardnacrusha belongs to ESB.
Shipping in Shannon estuary has developed a lot in the 1980s, with over IR £ 2 billion (€ 2.5 billion) investment. A tanker terminal at Foynes and an oil jetty vidShannon Airport was built. In 1982, a large-scale aluminum recovery plant was built at Aughinish. 60,000 tons of cargo ships carrying crude now bauxite from West African mines to the plant, where it is refined into alumina. This is then exported to Canada where it is further refined to aluminum. 1985 inaugurated a 915 MW coal-fired electricity plant in Money Point, fed by regular visits by 150,000 tonne bulk carriers.
Shannon eel management software
A trap and transport system in force Shannon as part of an eel management software following the discovery of a reduction in the eel population. This system ensures safe passage for young eels from Lough Derg and the Shannon Estuary.  
Although Shannon estuary fishing industry is now over, at one time employed hundreds of men along its length. At Limerick, fishermen based on Clancy Strand used Gandelowatt catch salmon.  In the 1920s, the construction of a dam at Ardnacrusha seriously affected the salmon farming and that, and the introduction of quotas, had in the 1950s caused the salmon to an end.  but go recreational fishing is still on. Further down the Shannon estuary at Kilrush the Currach used to catch herring and operating networks for salmon.
- Shannon River Basin
- Shannon Airport
- Shannon Town
- Cromwellian conquest of Ireland
- Shannon Callows
- Rivers of Ireland
- List of Loughs in Ireland
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