Tag Archives: weir

Tarmonbarry 1851

To the Editor of the [Dublin] Evening Mail

Sir

In your impression of the 3d instant, under the head of “The Famine Advances and the English Press”, I find a reference to the (so called) improvement of the Shannon; that of the sum of £313009 advanced by government, £230325 has been repaid. In this case you say (and most truly say) “the jobbing was most flagrant, and the reckless waste of the public money unparalleled”.

So far you are correct, but you are, no doubt, labouring under a very common mistake when you say the works have very recently been completed, such not being the case. Some handsome bridges, with swivel arches, and spacious locks — one in this neighbourhood too small to admit an ordinary river steamer. Nor was the level properly taken, there not being sufficient water to carry tonnage drawing more than 5 feet 6 inches, during the greater part of the summer.

Now, I should wish to know, through your well informed medium, to what cause is to be attributed the present state of the weir, or lock dam, adjoining Tarmonbarry, a span of nearly 500 feet. Owing to the improper manner in which the same has been executed, upwards of 60 feet have given way, and when examined by the engineer of the board, the entire is found in such a state as will involve the rebuilding.

In justice to this gentlemen, I am bound to say he was not the engineer under whom it was constructed, nor do I think, until very lately, he had anything to do with the Shannon Commission, every work in which he has been engaged, being acknowledged to be well executed.

I am not aware whether you are in possession of this fact, that in order to make the Shannon improvements available or remunerative, it has been considered necessary to construct a canal to “Lough Erne”, adjoining Belturbet, and thence to communicate with Belfast, by “the Ulster canal”. You will, I am sure, agree with me in the old adage, that “this would be going round the world to look for a short cut”; but the cut I allude to is not so short, as it involves, I am informed, thirty miles of new canal, and several large and expensive locks.

But, Sir, I must inform you, that the tolls of the river Shannon, from Carrick-on-Shannon to Limerick city, are barely sufficient to pay the lock-keepers’ salaries. The Shannon Commission I would henceforth style “the Shannon job”.

I remain, Sir, though a bad dancer, one who must

Pay the Piper

[Dublin] Evening Mail 17 November 1851

From the British Newspaper Archive

What’s a cumec, Daddy?

I don’t know, but here’s a picture of 415 of them flowing through Castleconnell. [Update 13 December: that may be only 405 cumec.]

Castleconnell 20151212 10_resize

415 cumecs on 12 December 2015

Actually, a cumec is one cubic metre of water per second, which is roughly one ton per second, which is a lot of water. And 415 cumec is the amount that, according to the blatts, the ESB is currently letting down the original course of the Shannon from Parteen Villa Weir; the minimum flow in that channel, as seen in summer, is 10 cumec.

Castleconnell 12 December 2015

Castleconnell 20151212 02_resize

Younger trees getting their feet wet

Castleconnell 20151212 11_resize

Who’d have guessed?

Castleconnell 20151212 14_resize

Below the bridge

Castleconnell 20151212 21_resize

Above the bridge

Castleconnell 20151212 34_resize

Stormont

Castleconnell 20151212 37_resize

Pump

Castleconnell 20151212 40_resize

Sandbags

Castleconnell 20151212 42_resize

Sandbag Central

Castleconnell 20151212 43_resize

Sandbags filled here for distribution

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Army engineers

Castleconnell 20151212 50_resize

More equipment arriving

Clonlara 11 December 2015

Headrace Clonlara 20151211 01_resize

Ardnacrusha headrace, said to take 400 cumec

PEC Errina Bridge 20151211 04_resize

Errina bridge on the Plassey-Errina Canal

PEC Errina Bridge 20151211 01_resize

The stop planks seem to be quite effective …

PEC Clonlara upstream 20151211 01_resize

… as there is little water getting down the canal to Clonlara bridge

Park Canal 9 December 2015

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Depth gauge at Park Lock

Park Canal 20151209 03_resize

Lock chamber

Park Canal 20151209 04_resize

Full canal upstream

 

Why the Shannon floods

From the search terms used, it seems that many people are visiting this site with questions about Parteen Villa Weir, water levels, Shannon floods and so on. They are not this site’s primary focus, but some non-technical information might be of interest.

The best place to start is with a map of the Shannon International River Basin District. As the Shannon RBD site says,

The Shannon International River Basin District is the largest in Ireland at more than 18,000 km2 in area. It covers the natural drainage basin of the Shannon river itself, stretching from the source of the River Shannon in the Cuilcagh mountains in Counties Cavan and Fermanagh to the tip of the Dingle peninsula in north Kerry. It also includes coastal parts of Kerry and Clare which drain to the sea. It flows through 18 local authority areas and is also an international RBD as a small portion of County Fermanagh in Northern Ireland drains underground to the Shannon Pot.

The district is about one fifth of the area of the island, one quarter the area of the state. Rain that falls on that area of land ends up in the Shannon (or in a few small rivers in Clare and Kerry that flow to the sea). Some goes to the Shannon estuary or its tributaries; most flows into the non-tidal Shannon, which means the river upstream of Limerick.

The nature of the Shannon

Ireland has been described as saucer-like, with a high rim and a low flat centre. It’s not entirely true, but there certainly is a very large central plain, and the Shannon flows down through the middle of that. And, because the land it flows through is flat, the river falls very little.

In 113 miles from Leitrim to Killaloe, the Shannon falls just over 30 feet; the navigation channel needs only five locks. [By way of contrast, the Thames has 45 locks over 135 miles; the Trent has 12 locks over 42 miles.] So extra rainwater allows the Shannon to spread out, covering a much wider area, and it takes time for that water to drain away downstream. But many of the rivers that flow into the Shannon have been subjected to drainage schemes, so they can get rid of their flood waters quickly … into the Shannon.

Why don’t they open [or close] the weirs?

There are some weirs on the Shannon, designed to keep a minimum depth in the river for navigation; there are also some natural obstacles that hold water back. But once the level has risen high enough, water simply flows over the top of the weir, and there is nothing useful anybody can do — apart, of course, from farmers’ representatives and politicians, who can always make use of a photo opportunity.

The bottleneck

Almost all the water that enters the non-tidal Shannon will eventually flow through Killaloe, the town at the southern end of Lough Derg [it’s on the west bank, in Co Clare; the east bank is Ballina, in Co Tipperary].

As James Robinson Kilroe wrote in 1907,

[…] we have the formidable barrier at Killaloe, naturally damming up a considerable depth of water in Lough Derg, and the river falling away southward by a series of rapids which correspond with drops in the canal, south of O’Briensbridge […], along an alternative course, possibly one used by a branch of the Shannon.

The diagrams with that article are worth a look.

In the twelve Irish (fifteen statute) miles between Killaloe and the tidewater at Limerick, the river falls about 100 feet: more than three times its fall from Leitrim to Killaloe. In the nineteenth century, the water level at Killaloe used to change by about eleven feet between summer and winter — even without storms.  The old Limerick Navigation, including the canal Kilroe mentioned, could drain only a small amount of water (which could put the navigation out of action); the rest went down the river’s original course through the Falls of Doonass.

The relief channel

Nowadays, the Falls of Doonass are a shadow of their former selves, and the water level through O’Briensbridge, Castleconnell and Plassey is much below its previous levels. I suspect that the older, larger trees along the river show the original level, with the newer, smaller trees having grown since the 1920s.

The cause was the construction of a relief drainage channel in the 1920s. This channel is controlled by a weir at Parteen Villa [not to be confused with Parteen]. Switch between the modern Street Map and the Historic views here to see what has happened.

Actually, of course, it’s not a relief drainage channel. The weir [sometimes referred to as the Hydro Dam] controls the flow of water to the original course of the Shannon [the right-hand or eastern channel, which gets the first 10 cubic metres of water per second] and the headrace for the hydroelectric power station at Ardnacrusha [the left-hand or western channel, which gets the next 400 cubic metres of water per second, 100 for each of its turbines]. The power station was built to use that 100-foot fall of the Shannon, concentrated between Killaloe and Limerick, to generate electricity.

But one effect of the construction of Ardnacrusha was to provide a channel, the power station headrace, capable of taking [at least] 400 cubic metres of water per second away from the original river channel, thus reducing the likelihood of flooding.

Cumec

Water experts talk about cumecs: a cumec is a flow of one cubic metre, or 1000 litres, of water per second. And a cubic metre of water weighs about one [metric] tonne, which is roughly the same as an imperial ton. So one cumec is one ton of water per second, which is a lot.

It was said, on 8 December 2015, that the ESB, using Parteen Villa Weir, had released 315 cumec down the original course of the Shannon on the previous day and had increased that to 375 cumec. If the Ardnacrusha headrace was getting 400 cumec, then the amount of water being discharged from Lough Derg and the upper Shannon had doubled.

Floods

As far as I can see, the Shannon has always flooded. The 2009 floods affected some nineteenth century houses, which I guess would have been flooded even worse before Ardnacrusha was constructed. However, I suspect that more houses have been built on the flood plain since then. But I don’t see that there is any way to prevent Shannon floods.

Envoi

There is a good article in the Irish Times of 9 December 2015; it will no doubt disappear behind a paywall at some stage.

Here is an ESB infographic about the Shannon.

Hamilton Lock

Victoria (Meelick) and Hamilton Locks (OSI ~1900)

Victoria (Meelick) and Hamilton Locks (OSI ~1900)

Lord Dunkellin: Do you know the Victoria lock at Meelick?

Sir Richard Griffith: I do.

Victoria Lock, Meelick

Victoria Lock, Meelick

Dunkellin: Do you know what is called the Old Cut, the old canal?

Griffith: Yes.

Dunkellin: The Victoria lock is a new work, is it not?

Griffith: It is.

Dunkellin: Should you be surprised to hear that vessels do not use that frequently, but go by the old cut?

Griffith: In times of very high flood I am aware that the canal boats find it advisable and beneficial to go by the Hamilton lock, on the old cut, in preference to the other.

Dunkellin: Prima facie, one would have thought that a new work like the Victoria lock would have the effect of regulating the state of things?

Griffith: It arises from the Counsellers’ Ford, as it is called, above Meelick; it has not been sufficiently excavated, and there is a strong current, and the boats are not able to get up to it in times of high flood.

Dunkellin: Then the boats made use of the old canal instead of the new lock?

Griffith: Under those peculiar circumstances they did.

Evidence of Sir Richard Griffith to the Select Committee on the Shannon River 12 June 1865

My OSI logo and permit number for website

Interesting info from Waterways Ireland

Two interesting PDF documents available on this page:

No mention of Saunderson’s Sheugh, but I suppose dredging of the River Finn is proceeding.

Backtracking the Barrow trackway

Some time ago I put up a page about the Barrow trackway [towing-path]. For some reason, the page disappeared shortly afterwards. I have now recreated it; unless or until it disappears again, it is here.

Waterside Belturbet

Here is a small amount of information about Belturbet and some of its industrial heritage. The photos were taken on a brief visit in July 2011.

Crossing the Barrow

The trackway [towing-path] on the River Barrow changes from the east {left) bank to the west at Leighlinbridge and back again at Graiguecullen/Carlow.

It seems to me that there may have been some difficulties in getting horse-drawn boats from one side of the river to the other and I have found no evidence on how it was done, so here is some speculation instead.

The Deel navigation

The Deel linked the Co Limerick town of Askeaton to the south side of the Shannon Estuary. Here is a page about the navigation and some of its quays. Note that it is a long page with many maps and photos, although they’re all reduced in size to minimise the strain on tinterweb.

The Shannon in winter

Downriver from Shannon Harbour to Dromineer in December 2014. It began as a bright, cold morning.

Shannon Harbour to Dromineer December 2014 01_resize

Leaving Shannon Harbour after icebreaking between the locks

Shannon Harbour to Dromineer December 2014 02_resize

Flooding to the south-east

Shannon Harbour to Dromineer December 2014 03_resize

But southward, look …

Shannon Harbour to Dromineer December 2014 06_resize

The Brosna

Shannon Harbour to Dromineer December 2014 73_resize

Heading for Banagher Bridge 1

Shannon Harbour to Dromineer December 2014 75_resize

Keeping close to the pontoons

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Heading for Banagher Bridge 2

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Heading for Banagher Bridge 3

There is a YouTube video of the shooting of the bridge here. It seems to start automatically, including sound; I don’t know how to avoid that.

Shannon Harbour to Dromineer December 2014 107_resize

Looking back at Banagher

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Colours

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Invernisk

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Shannon Grove

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Current

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Scarpering heron

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Colours

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Marker and gauge

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House

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Boats at Meelick

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Meelick weir

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East bank

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Protective boom

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Sluices

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Through Meelick Lock

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One bird

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Many birds

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Reeds

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Architecture

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Munster Harbour

Shannon Harbour to Dromineer December 2014 233_resize

Delaying Eamon Egan

Shannon Harbour to Dromineer December 2014 235_resize

Gateway to civilisation

Shannon Harbour to Dromineer December 2014 237_resize

Connacht Harbour

Shannon Harbour to Dromineer December 2014 239_resize

Lough Derg: weather has changed

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Journey’s end, Dromineer