Tag Archives: water level

Shannon lake levels

According to the Shannon Catchment-based Flood Risk Assessment and Management (CFRAM) Study Technical Assessment: River Shannon Level Operation Review [PDF: Office of Public Works v2_0 July 2012]

ESB collects and maintains records of rainfall, river and lake levels and flow data. Even though ESB has no responsibility to supply flood warnings under their regulations, it issues twice weekly lake level forecasts to all the relevant stakeholders since 2010.

Those stakeholders include Waterways Ireland.

As the levels of the lakes are of great interest to boat-owners and others, it would be really nice if either the ESB or Waterways Ireland were to publish those forecasts. WI wouldn’t need any elaborate new system: they could send them around as marine notices, and the cost would be minimal.

But perhaps the forecasts are already published somewhere? If, Gentle Reader, you know where they are, do please leave a Comment [preferably with a link] below.

Limerick water levels 14 December 2015

The Abbey River

Abbey Bridge 20151214 01_resize

Abbey Bridge

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Baal’s Bridge

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Mathew Bridge

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Current heading for Mathew Bridge

The Shannon in Limerick

Shannon in Limerick 20151214 02_resize

The weir

Plassey

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Lots of pumps running and equipment trundling about the place

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Trouble at t’mill

Plassey Millstream 20151214 01_resize

T’millstream

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Cots on the bank

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The Black Bridge getting another hammering

Annacotty

I have been told that the Mulkear River rose very rapidly on Saturday night and that, at one time, it was feared that the (older) bridge would be swept away. I gather that folk working in other areas were called to Annacotty to deal with the emergency.

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The old bridge at Annacotty (downstream face)

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A tree in the water above the bridge

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There’s a weir in there somewhere

The Mill Bar in Annacotty was closed today after being flooded.

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The Mill Bar

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This, from a small garden beside the bridge, suggests that the Mulkear may have carried and deposited a lot of silt

The Park Canal

I gather that the Mulkear’s waters, added to those of the Shannon itself, raised the level of the Park Canal (the bottom section of the Limerick Navigation). A problem with opening the lock gates, to release the water, meant that a few houses in Corbally were flooded. A Sinn Féin councillor, whose party colleague has been responsible [with her southern counterpart] for slashing Waterways Ireland’s budget in recent years, is quoted as saying

I am in no doubt it was primarily caused by the ineptitude of Waterways Ireland.

Alas, the news story does not tell us the source of the councillor’s certainty.

The article also says that

[…] the force of this water meant it was not possible to open the lock gates by hand.

That is, I think, misleading: neither set of gates has gate beams, so they are not opened by hand.

park canal mist 03_resize

The upper gates in 2004, shortly after installation. Note the absence of gate beams. Note also the two sluices or paddles on each gate

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Control pedestal and gear

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The upper gates open today

I see no sign of the paddles or sluices. Perhaps the level is so high that they’re underwater. I must try to check next time I’m at the canal harbour.

Canal lower lock floods 20091128 1_resize

The upper gates in the floods of 2009

In the floods of 2009 the upper gates were held slightly open and all four sluices were discharging water. That would have lowered the level in the canal; it would also, I think, have made it easier to open the gates fully.

I am guessing, but I imagine that on Saturday night some sort of hydraulic machine was brought in this way …

Park Canal 20151214 21_resize

Two bollards have been moved from the gateway and stacked beside it

… and used to push or pull open the near-side upper gate. There seems to be some slight damage to the stone and iron work.

Park Canal 20151214 10_resize

Slight damage

One other possibility that struck me is that silt from the Mulkear might have built up behind the gates, making them difficult to open, but I have no evidence on the matter.

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The lower gates

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From the outside looking in

 

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.

Shannon water levels 8 December 2015

North to south (more or less)

Floods 20151208 Shannonbridge 01_resize

Shannonbridge upstream

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Shannonbridge downstream

Floods 20151208 Shannon Harbour 04_resize

Shannon Harbour: 36th lock

Floods 20151208 Shannon Harbour 06_resize

Shannon Harbour: below the 36th

Floods 20151208 Shannon Harbour 16_resize

Shannon Harbour: road to Banagher closed

Floods 20151208 Banagher 03_resize

Banagher: the harbour above the bridge

Floods 20151208 Banagher 05_resize

Banagher: the harbour’s sole inhabitant

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Banagher: work goes on

Floods 20151208 Portumna bridge 01_resize

Portumna Bridge: Hawthorn moving

Floods 20151208 Portumna bridge 03_resize

Portumna Bridge

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Below Portumna Bridge

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Above Portumna Bridge

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Portumna Bridge: Waterways Ireland yard

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Mountshannon

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Mountshannon: the main quay

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Scarriff: the river in flood

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Scarriff: the river flowing on to the road to the harbour

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Scarriff: sandbags blocking the road …

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… to the Waterways Ireland Shannon HQ. Anyone in the building must have waded there

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Tuamgraney

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Killaloe: the flash lock

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Killaloe bridge from downstream

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O’Briensbridge

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Water level with the quay at O’Briensbridge

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Flooded fields at O’Briensbridge

O’Briensbridge is on the original course of the Shannon, downstream of Parteen Villa Weir, which controls how much water goes via the original course and how much goes to the hydroelectric power station at Ardnacrusha.

Normally, the original course gets the first 10 cubic metres per second (10 cumec, they say) of water and Ardnacrusha gets the next 400, 100 for each of its four turbines. In floods, any excess is sent down the original course, through O’Briensbridge, Castleconnell and Plassey. One newspaper today said that, on Monday 7 December 2015, 315 cumec had been sent down the original course and, on Tuesday 8 December, 375 cumec.

The water levels are still below the peak achieved in November 2009, but there is more to come: as the Shannon drains a very large amount of Ireland, and as it is falls very little in its upper reaches, it takes a long time for the runoff to reach Killaloe and Parteen Villa. It may be that the ESB, which controls Ardnacrusha and Parteen Villa, is now running down the level of Lough Derg to make room for the water that has yet to arrive from the upper 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

ESB and the Shannon

I wrote here that I had written to the ESB, on 27 May 2015, to ask about navigation on the Shannon from Castleconnell downstream. One month later, I have not yet received a reply.

I did hear this weekend that ESB had contacted certain boat-owners to inform them that they were not to moor to the ESB embankments between Portumna and Meelick. As a riparian landowner, ESB is no doubt within its rights, but it would be interesting to know how much of the bed of the Shannon it claims to own in that area.

I have still not been able to find out, from the ESB, the clearance under its high-voltage lines crossing the Shannon (and other navigations). I gather that the ESB works on the principle that, if it provides no information, it can’t be blamed if owners of masted vessels electrocute themselves, whereas if it did provide information it might be sued. Strange that a public sector body should have such a blasé attitude to the prospect of the electrocution of the citizenry.

Perhaps if I asked questions under the Access to Information on the Environment Regulations 2007/2011 I might get replies.

 

Hard sums on Lough Derg

According to the Clare Champion, a Clare county councillor called Pat Hayes, who is a member of Fianna Fáil [an excitable lot, Fianna Fáil], is boycotting something or other for some reason that is not clear to me [and, to be honest, is probably entirely unimportant]. Mr Hayes thinks that water from Lough Derg should be sent to the Atlantic, where it is wasted, rather than to Dublin, where it might be used, and the newspaper cites the River Shannon Protection Alliance as estimating that

… up to 350 million litres of water could be taken from Lough Derg by 2030.

The River Shannon Protection Alliance itself doesn’t agree with those figures. It says:

The central principal and immediate purpose of the organisation is to prevent the proposal of Dublin City Council to abstract in excess of 350 million litres of water on a daily basis from Lough Ree on the river Shannon, and to oppose any action that may be harmful to the well being of the river Shannon system. Since then, the abstraction options have been considered and the current recommended proposal is to abstract upwards 500 million litres of water from Lough Derg and store it in a depleted bog hole to be developed by Bord na Móna at Garryhinch bog, (near Portarlington) where the water will then be treated and pumped on to Dublin.

Eek. That’s a bignum: a lot of litres. Let’s all panic.

On the other hand, 500 000 000 litres is 500 000 cubic metres. Each of Ardnacrusha’s four turbines uses 100 cubic metres per second. So the amount of water to be sent to Dublin every day is less than Ardnacrusha uses in 21 minutes.

If the Alliance wants to save the Shannon, shouldn’t it be trying to get Ardnacrusha closed down first?

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.

Interesting information about the Ulster Canal …

… as distinct from ministerial reelection photo opportunities.

By the way, some folk get confused about the location of the Ulster Canal; this map may help:

Saunderson's Sheugh -v- the Ulster Canal (OSI ~1840)

Saunderson’s Sheugh -v- the Ulster Canal (OSI ~1840)

Anyway, for folk who are interested in weightier matters than ministers talking through portions of their anatomies that they can’t distinguish from their elbows, here is some speculation about opening bridges on the Ulster Canal.

That’s the Ulster Canal Ulster Canal, not the Saunderson’s Sheugh “Ulster Canal”, by the way.

My OSI logo and permit number for website

 

Sinn Féin, the boaters’ party

Phil Flanagan [SF, Fermanagh and South Tyrone]:

AQW 42148/11-15 To ask the Minister of Culture, Arts and Leisure what consideration has been given to establish a forum to discuss policy around the management of Lough Erne.

AQW 42149/11-15 To ask the Minister of Culture, Arts and Leisure how Waterways Ireland work with Rivers Agency to ensure that, during times of changing waters levels as decided by Rivers Agency, Lough Erne remains navigable for cruisers.

I thought the ESB had something to do with that last one.