Shannon floods at Limerick – the role of Ardnacrusha

How the power station affects the river

As tempers rise to match the River Shannon floods, much anger is focused on the Ardnacrusha hydroelectric power station and its associated dams, reservoirs and channels. Although many readers will already have a detailed knowledge of its design and layout, for those who don’t I thought it might be useful to provide a quick summary of the scheme and offer a few rough calculations of my own.

Aardnacrusha power station

When the Shannon Scheme began operation in 1929, it was the largest hydroelectric station in the world, but perhaps more significantly for the government of the day, it was a huge statement of intent for a newly-independent country and a great gamble, since it cost more than one fifth of the State’s entire annual budget to construct. What’s more, with an initial generating capacity of 35 megawatts, later increased to 85 megawatts with the addition of a newer and more efficient fourth turbine, according to the project’s detractors Ireland would never need so much power. There were even some who condemned the project on the grounds that it amounted to Communism, much as the same people would later attack the Mother and Child Scheme, but that was Ireland for you.

Shannon scheme Power house
Power house

Ninety years later, Ardnacrusha contributes about 2% of the total ESB output– enough for a town the size of Ennis.

It didn’t come without a social cost either, as I outlined in this post. They were hard days, different times and attitudes to workers were at best callous.

Aradnacrusha works canteen


Thomas McLaughlin, the man behind the scheme, was 29 years old when his project began. A man with little interest in non-academic pursuits, he had achieved a PhD in engineering and a collection of influential friends from his college days who would become instrumental in persuading the government to invest in the scheme.

McLaughlin wasn’t the first to propose using the lower Shannon for power generation. As early as 1844, Robert Kane was pointing out the opportunity for hydro power  presented by the drop in water level between Killaloe and Limerick. Potential energy, quite literally. But it wasn’t until John Chaloner-Smith’s research on river flows was published in 1921 that the hard research became available to design a workable scheme.

McLaughlin’s plan, developed with Siemens, required a dam at Parteen Villa (not to be confused with Parteen), just south of Lough Derg, to impound the lake and turn it into a reservoir.

Shannon scheme

From the dam, a 12-km canal, the head-race, diverts most of the Shannon’s water to the power station at Ardnacrusha where it falls nearly 30 metres  through pipes 6 metres in diameter, the penstocks, to drive the turbines.  The water leaving the power station runs along the tail-race, a 2-kilometre channel blasted out of solid rock until, at Corbally, it rejoins the old River Shannon which was reduced to a trickle by the diversion.

Shannon scheme


parteen weir
Parteen Weir

Before moving on, I have to acknowledge that the scheme is a magnificent engineering achievement by any standards and even today, almost a century later is still deeply impressive. Nothing like it had ever been seen  in Ireland before.

Siemens plant arriving at Limerick docks for Shannon scheme
Unloading at Limerick docks

Revealingly, the main contractor, Siemens-Schuckert, came from a country that was being crushed under punitive war reparations imposed by the Treaty of Versailles, and yet that was the reason why Germany was so active in developing hydro-electricity.: France had control of all the German coal-fields  Ireland’s infrastructure was so primitive that all the construction equipment had to be shipped from Germany because none existed here.

Everyone will have an opinion on the reasons why Ireland was so primitive compared to England, Wales and Scotland, but it’s hard to escape the conclusion that the London government prior to 1922 had little interest in promoting industrialisation in Ireland, apart from Dublin, Belfast and perhaps Cork.

According to Siemens, they imported the following:

6 Large multiple bucket dredgers on rails each about 220 tons
3 Large bank building machines on rails each about 240 tons
27 Smaller dredgers and shovel excavators on rails and caterpillars
130 Steam locomotives
8 Electric locomotives
31 Portable air compressors
13 Portable concrete mixers
8 Tower cranes
3 Cableways, each 310 m long
1,770 Railway wagons
20 Road trucks
31 Barges, trugs, launches and pontoons
Temporary power station, Ardnacrusha
Temporary power station

In order to construct the power station, it was first necessary for Siemens to build a power station with nine diesel generators producing nearly 3 megawatts. They also built a large engineering shop,  a smithy, a joiner’s department in addition to a tool-making shop and a welding shop.

Only when everything was in place could the project begin.

By law, the ESB is contractually obliged to guarantee a flow of only 10 cubic metres per second along the old course of the river, which is just one-fortieth of the volume it abstracts for the power station, and this has led to many different problems, both hydrological and environmental. With such drastically reduced flows, there has been a great amount of encroachment by alluvial forest, with alder, ash and willow clogging the river and causing major blockage when it floods. On top of that, the scheme killed what was once a world-famous salmon fishery and an eel-fishing industry.

Now, a few figures.

The average annual flow of the Shannon is a little over 200 cumecs (cubic metres per second), so the ESB wouldn’t always get its full 400 cumec flow, nor would it wish to. But in a flood it could take that much while leaving the old river bed untouched. If the flow goes above 410 cumec then the next step is to store the flood in Lough Derg, using the Parteen Weir, and releasing the extra water gradually down the old channel. All well and good until we get flows of 800 cumec and more as we have today. That means 400 cumec down the head-race and the other 400 going somewhere else, but the question is where?

It’s often suggested that the ESB could have created storage by lowering the lake in advance of the storm, and that’s true, but no matter by how much the lake is lowered, eventually it will fill up and after that, any excess flow is going straight over the weir and down the old Shannon channel, because it has nowhere else to go. Therefore, the only hope is that they can create enough capacity to store the excess water until the rain subsides and the water stops concentrating in the river. It’s a relatively slow river, and we don’t see it peaking until several days after the rain has stopped.

The lake’s surface area is 130 million square metres. Its average volume is 887 million cubic metres and its average depth is 7.6 metres. This allows us to make a crude estimate of how much storage can be created by reducing the water level during periods when there is no flooding.

The current flow into the lake is 840 cumec. How much storage do you reckon we’ll need?

A half-metre drop would give enough storage to contain a day and a half of flood, after which the water would need to be released down the old Shannon. But will the flood only last a day and a half?

A metre would give three days storage.

1.5 metres would give protection against a flood lasting four and a half days. That’s a five-foot drop, in the old money. Is that acceptable to the people and businesses who rely on Lough Derg? What if the flood lasts five days? A week? Two weeks?

Furthermore, you don’t just lower the level of a water body like Lough Derg overnight. It takes weeks and you’d be doing it in contemplation of an event like Storm Desmond, which does not provide weeks of warning.

What are the other factors?

With the exponential growth in paved, impervious areas around the country — roads, car-parks, driveways, roofs and all the rest of it — rainfall no longer has so much time to percolate through the soil and gradually make its way to the watercourses.  With uncontrolled development, widely seen as A Good Thing, rainfall now concentrates in a flash, running straight down the gulleys, into the drains, out to the streams and into the rivers. Before you know it, you have a flood.

There’s the neglect of watercourses, as I mentioned. We could be clearing intrusive alluvial forest and replacing it with forestation on land.

Let’s not even mention climate change, but we all know it’s there and we all know it will lead to more of this.

The important thing to bear in mind is that there’s only a given, fixed amount of storage and you can make it as big as you want, but eventually a storm will come along that will fill it up and then the water will go where the water wants to go. Or to put it another way, the ESB can only delay the flood. It can’t prevent it.

Let’s remember something else. Shannon floods are nothing new. The river below Corbally has the same flow now as it did before the power station was built, though perhaps made worse by the factors I just mentioned. Whatever about upstream at Castleconnell, Montpelier or Plassey, Ardnacrusha is not to blame for flooding in Limerick City. In 1850, a fearful flood filled up all the basements of the houses and covered the quays in some places to a depth of three and four feet.  It even threatened to tear the parapets off Mr Nimmo’s fine bridge across the Shannon, which had been replaced at great cost following a similar catastrophe some years earlier.

None of this is intended to get the ESB off the hook, but it seems to me that if we’re to have a rational debate on the issue of flooding, at the very least we should be basing it on some sort of rational facts and figures, and we should be looking at all the factors involved. Of course, I do realise that the figures I have here are very crude, but in the absence of a complete hydrological model, I’m afraid they’re the best I can do for now.

shannon scheme
Excavating the head-race

shannon scheme

shannon scheme
Intake sluice house
shannon scheme
Constructing volutes to produce a tangential flow
shannon scheme
Parteen weir under construction

shannon scheme

shannon scheme
Head-race embankment
shannon scheme
Parteen weir



Old River Shannon

Irish Waterways History



Clare county library

National inventory of architectural heritage

History Ireland





46 thoughts on “Shannon floods at Limerick – the role of Ardnacrusha

  1. lets not forget the rivers downstream of Parteen Villa. As in the last few days they have added greatly to the water on the Shannon. It only takes about 12 hours for these rivers to add a metre or more to an already full Shannon as happened over the weekend

  2. Great detail – thanks.

    I wonder would it be possible to build some kind of “exit” from the Shannon towards the Atlantic (further north) with the required incline and dimensions to reduce the water levels appropriately. This immense flow of water could be used to generate more electricity before it hits the ocean.

    It would be a huge project – but surely spending a couple of Billion on a project like this (given current state of exchequer returns) would make sense…..

    A great project for an international ECO competition……

  3. How about holding back water in the upper catchments, creating buffer zones by streams, reconnecting rivers with flood plains and planting trees to retain water and stopping dredging.

  4. Take a look at land use around the river and its tributaries, particularly the Suck. Bog and forestry converted to pasture for grazing over decades and longer have removed natural reservoirs upstream and with nothing to soak up the water and slow release it you are left with all the upstream water with nowhere to go except downstream, fast. OPW rural drainage exacerbates the problem. Here’s my views on it:

  5. I like the analysis but you said by lowering the level of lough derg by 0.5M you could contain up to 1.5 days of flood. I think that means you could hold 500 cumecs for 1.5 days, If you were letting water off at maybe 350 cumecs in the Shannon you would only be building up at about 150 cumecs and you might get 5 days before you need to increase the flow in the river by.

  6. That’s correct, but when they were releasing 375 cumec there were still problems downstream of the weir.

    I must add another cell to my spreadsheet, but as I said, the figures are crude anyway. It’s all for the sake of promoting discussion.

  7. The Shannon basin is a flood plain – it’s like pouring water onto a dinner plate – it spreads out – ie it floods – because it’s a ‘flood plain’ it’s supposed to flood – – problem is this natural sponge has been stripped away by bord na mona – the river has been clogged up with peaty shit – the remaining marshes have been ‘reclaimed’ by subsidy junkies (aka farmers) – oh and the wildlife have been decimated – red grouse corncrake salmon – gone! And now we all blame climate change ….

  8. Could a tunnel be built eg from the North of Lough Derg straight towards the coast, perhaps exiting at the base of the cliffs of Moher (to provide adequate incline). This could be used to drop the levels of the Shannon further north.

    I think I heard on Primtime last night the Shannon only drops 15M through its whole lenght. If a tunnel were to come out under the sea then it would probably have considerably more incline and so would take away a lot of water.

    Today huge tunnels are being built under cities all over the world. For example the new Crossrail tunnel in London is 42km long. At a rough guess, a tunnel a little longer than this would reach from Loug Derg to Galway Bay. Of course it would cost a lot but much less than the London tunnels which are designed to carry passenger trains.

    I wonder if any engineers have considered it ?

  9. A tunnel 40 miles long from Lough Derg to the Cliffs of Moher.

    The world’s biggest water slide.

    That has to be a winner.

  10. some day last week on the radio, a guest speaker was saying that 380cubic metres a sec was being released through the dam into the river. without the dam the figure would have been 780 cubic metres per sec. when asked could the proposed pipeline to dublin help in reducing the water levels, he informed the listeners that the proposed pipeline could only take 4 cubic metres per second,when the flow into lough derg was 810 cubic metres per second.

  11. What about the impact of Parteen Weir on flooding upstream? Did construction of this weir increase the level in Lough Derg? If so that would obviously increase flood risk upstream.

  12. I had not seen John’s post above before I posted mine but basically I think our idea is the same.

    By the way Bock – I’m saying 42km not 42 miles (still long, but shorter).

    Maybe its a mad idea – but this problem needs a mad idea to solve it.

    Also, it could generate electricity.

    Also – as you say, it could be the biggest water slide of all time. We could ask Mick Wallace, Clare Daly, Bertie Ahern, Bono, and Marty Morrissey to be the first down the shoot…..After that could follow: Enda Kenny, Gerry Adams, Mary Lou… and a few others such as Pierce Morgan, Michael Flatley. Rosanna Davidson, Miriam O’Callaghan and a few more…..

  13. We won’t fall out over a detail of measurement when we’re discussing a tunnel through the Burren and diverting the Shannon away from Limerick City.

    By the way, you won’t get any advantage bringing your tunnel out under the sea. It will just fill up with sea-water. The fall in level won’t generate much more electricity than the existing power station since most of the hydraulic head is between Limerick and Killaloe.

    Wait. Why am I even debating this? I must be going soft.

  14. Hello All.
    It seems to me that a combination of dredging and the cutting back of the growth along the old watercourse, may well allow a greater volume to reach the sea in less time. A time of extraordinary high tides however; coupled with extraordinary rainfall on already sodden ground, would I presume, still cause the “back-up” one might expect. I was wondering about the possibilities of relieving some of the headwaters to mitigate the effects downstream.
    I confess to know nothing of this kind of engineering, other than something is required now.
    The frequency of extreme weather events seem to be on the increase, and my
    heart goes out to those affected by flooding.
    I believe it urgent for government to task appropriate engineers to formulate long term solutions, -if that be possible.

  15. That Monbiot article echoes points made in post # above. They both highlight the futility of trying to solve problems downstream that are caused upstream.

  16. Why do the esb leave water off on a full Spring tide, like filling a glass that’s full already, like what happened last year. The Shannon is tidal now up to Plassey ! Also if they got rid of the bung or dam in the park canal it would drain straight through to the abbey river.

  17. According to the World Bank, 2% of Ireland’s total electricity produced in 2010 came from hydroelectric sources. These figures show that we produced 557,000 MegaWatt Hours from hydroelectric in 2010.

    It is very difficult to ascertain just how much of this was produced by Ardnacrusha on its own. According the the ESB, if all our hydroelectric schemes were working at maximum capacity they would produce 512 MegaWatts every hour. In reality this far exceed actual generating performance due to the fluctuating nature of the water supply. Turlough Hill can produce 292 MW per hour of this but only for six hours per day. Indeed, Turlough Hill is a 25% net consumer of electricity.

    Ardnacrusha can produce 85 MW every hour which is only 17% of our hydro generating capacity. However, if we were to generously exclude Turlough Hill then, in a very crude way, we might say that, Ardnacrusha produces not more than 40% of our total hydro electricity. This amounts to 223,000 Mega Watt Hours. On that crude basis Ardnacrusha produces only 0.8% of our total electricity consumption. Enough to power a town the size of Longford.

    At €150 per MegaWatt hour, Ardnacrusha electricity accounts for approx €34 million of the annual turnover of the ESB.

    What is the annual cost of flooding to the communities along the Shannon? Does it exceed €34 million? Could we drain the Shannon for €34 million?

    I assume that Winter is the high season for generating at Ardnacrusha. But this is also the season when the ESB water-hoarding policy gererates the maximum pain for the Shannon community.

    We need to think about how to reduce ESB generation activities at Ardnacrusha during the Winter months. We certainly need to curtail the control which the ESB exerts on the communities along the Shannon.

    Should we close turbulent Ardnacrusha once and for all?

  18. Seamus, there is about 450 cumec flowing down the old channel right now. If the power station were decommissioned an additional 400 cumec would be sent into the flooded areas. How would that relieve the problem?

  19. Bock,
    the dam at Ardnacrusha would surely be more than capable of taking a much higher flow of Shannon drainage if the water was not being restricted to 400 cumecs by the 4 turbine tubes.

    The top of the dam is 100 meters wide. It would be interesting to get some engineer to calculate how much water would pass over if the power station tubes were sealed and the height of the dam was lowered to a height which would fit in with water height at say Killaloe.

    Consider this:

    1. Seal up the turbine tubes at Ardnacrusha.
    2. Reduce top of the Dam to make it a waterfall-dam to allow a greater flow.
    3. Use existing weirs, locks and waterways to keep Shannon at boating levels during Summer,
    4. Open weirs and locks gradually during Autumn to bring levels back down to safe levels.
    5. Restore boating levels in Spring.

    By making a waterfall at Ardnacrusha it might be possible to regulate the flow to rehabilitate the old Doonass falls.

    Ardnacrusha as a Power Station is not viable in modern Ireland. It is an artificial restriction of water flow which is causing terrible social problems every year.

    All of this is happening so that we can generate a paltry amount of electricity.

    Lets use Ardnacrush as a proper dam to control Shannon levels.


  20. In essence, the ESB is using Ireland’s Midlands as a giant sponge.

    The ESB gambles that it can control the level of water in the sponge so as to hoard generating water for the following Summer.

    It gambles that it will not be overtaken by high rainfalls. When the rains arrive, the turbine tubes in Ardnacrusha cannot clear flooding fast enough.

    Ardnacrusha is a museun piece which is causing terrible social problems. It is a most inefficient and troublesome way to generate a tiny amount of electricity.

    Ardnacrusha as a power station must cease operations if it is assist in developing the Midlands of Ireland. Who knows it might become a museum to the vigour and vision which put it there in the first place.

    Lets try and work with the Shannon as a great river, a tourism resource, an ecosystem and a natural resource for draining the farms and homes of the midlands.

    A waterlogged region does not need a dam, it needs a waterfall!

  21. It couldn’t really be a museum. To make your idea workable, the generating hall would have to be removed entirely.

    Have you done calculations on this?

  22. I feel an Interpretative Centre coming on!

    Yeah the plant would have to go. What I see is a waterfall which would be just high enough to maintain a decent flow in the head race with some left over to divert via Parteen Weir with the aim of attempting to regenerate some significant elements of Doonass falls and the old river.

    I haven’t done calcs as I’m not an engineer but surely we can produce a modern “improved” version of the river on the lines of what existed pre- Ardnacrusha. At least we would not have to contend with unstable stores of water upstream waiting to flood in Winter. I see a “normal” river.

    There is a natural geological dam at Killaloe which is the historical impediment to the flow from Lough Derg. That dam consists of extremely durable rock. However I believe that they made some progress in skimming the top off it when building Ardnacrusha. I have the theory that if the Shannon level were brought down to that rock that there might be an improvement upstream at Athlone at least. But thats a guess!

    I would be really interested if some fluid mechanics expert would attempt to calculate what volume of water could pass over the top of a lowered Ardnacrusha dam. I would hope that it would be a multiple of 400 cumecs.

    The beauty of all this is that we would still have a very extensive water level infrastructure in the form of weirs and locks. This would hopefully be adequate to satisfy tourism, boating etc Not sure how fishing fits in.

    Solutions being bandied about all seem predicated on the continued operation of the ESB hydroelectrical generating. I think that is the core problem.

    Ardnacrusha was fine 80 years ago. But I doubt if any engineer would propose (or be allowed to propose) such a scheme in today’s Eco Ireland.

    The political climate for my suggestion might now be at hand!

  23. The headrace would easily be able to accommodate twice the existing low. It’s a huge waterway as you know.

    But the problem for me is this. Even if you demolished the power station, the tailrace isn’t nearly as big as the headrace, and I think you’d just end up flooding Clonlara from the other side as well as the areas around Parteen and Ardnacrusha if you tried to use it to take the excess water.

  24. Bock,

    The tailrace was built to cope with 400 cumecs. Perhaps it was over-engineered and can take more. I don’t know the area but it appears from Google Maps that the tailrace has carved out a impressive channel down to the city.

    I suppose what I am really saying is that if we stop hoarding water in Loughs Allen, Ree and Derg during the Winter, the following may happen:

    The watertable on lands adjoining the river and lakes will drop and the land will absorb and release water more slowly than at present.

    In times of heavy rainfall once the water reaches the rivers it will drain through the system immediately, and faster than at present.

    There will be no build-ups of water which eventually have to be released in a catastrophic and non-gradual way.

    As i have said, I am no engineer but it strikes me that the 800 plus cumecs are the result of longterm hoarding and panic releases.

    Essentially, I am saying that, if we free up the dam at Ardnacrusha and stop hoarding, then the water will reach Parteen weir in smaller quantities which will fluctuate depending on the real-time rainfall.

    As I said before, I am hoping for a “normal” pre-Hydro river below Killaloe with most of the flow going over a lowered waterfall at Ardnacrusha. We built a magnificent head race which has the potential to be a fine river if we would only allow the water to flow naturally through it without any interventions upstream.

    The idea of Ardnacrusha sounded great at the time but would we really build such a monster today? If not, why do we continue to feed the monster?

    We badly need an engineer on board !

  25. I think a hydrologist would be better.

    The tailrace hasn’t carved out its channel. That’s how it was excavated in the construction of the scheme.

  26. Out of my depth here!

    We need a model on what what the flow pattern would be if the Winter storage of water upstream were to cease. Maybe such a model exists already?

    Dredging may be the option on the east side of the river below the tailrace.

  27. Lower the level of Lough Derg by a few metres in the winter months, and I suspect that the flooding problem between Limerick and Athlone would be largely solved. The only downside, as far as I can see, is that much less electricity would be generated at Ardnacrusha during that time.

  28. The average depth of Lough Derg is 7.6 m. If you reduced it by 20%, you’d create storage for about 11 days of rain after which the downstream flow would be as it is now.

    What depth reduction would be acceptable to people living around the lake?

  29. Why are we storing winter water in a river which is low lying and prone to serious flooding?

    The main reason seems to be so that the ESB can have water reserves for a minor power station which would never get built in today’s Ireland.

    Ardnacrusha produces only 0.8% of our aqnnual electricity. That electricity sells for €34 million annually. Can we put a price on the misery and economic damage caused by Shannon floods?

    There have been many expensive studies on this topic. Has there ever been a study on the feasibility of decommissioning Ardnacrusha?

    We are storing water to feed a historic monster.

  30. We wouldn’t be looking for storage though. What matters is that we have a buffer. We’d still be discharging it to the sea at every opportunity, so it’s not a case that if it rains for 11 consecutive days we’re in the same situation as we are now.

  31. I agree that’s a crude estimate, but it sets the thing in context. Getting rid of Ardnacrusha I think is unlikely to solve a problem that has many contributing factors.

  32. Ardnacrusha plays a very important role in mitigating flooding in this region, and further upriver too, so we definitely shouldn’t get rid of it. If it was operated solely on this basis then there’s every chance we wouldn’t have these floods, in my opinion. However, it isn’t operated solely on that basis. It is required to generate electricity, and to keep the levels of Lough Derg high in order to do so. Until we see the operation logs of Ardnacrusha we’re unlikely to be able to have a more informed discussion. How would we go about getting these? I think the ESB is exempt from FOI and I know they have previously refused to release this data.

  33. Brian Leddin,

    You’re spot on. We do not need to store winter rains. Let the water through and let the river take its course. I am aware that this must include prudent management of the river using existing infrastructure weirs, dams etc.

    (Yes, I am very keen to get an exact handle on how many MegaWatt hours of electricity is generated and delivered annually by Ardnacrusha. This seems an impossible task. I have estimated that Ardnacrusha contributes only 0.8% to our annual production. If I am wrong, I’m sure the ESB will set me right. Lets have some transparency and accountability).


    Ardnacrusha is a significant part of the infrastructure and I am not advocating that it be removed. However, as you know, it has one significant problem – its four turbine tubes can only take a max of 400 cubic meters of water per second (400 cunecs).

    In summer this is not a problem when most of the Shannon flow goes straight through these tubes.

    The problem arises during winter flows and particularly when the ESB is forced to “dump” large quantities of water which it has dammed up in Lough Derg and further upstream.

    The flow coming out of Lough Derg at present is approx 800 cumecs – double the quantity which can get through the tubes. Therefore, using Parteen Weir, the ESB is forced to divert the extra water down the old neglected course of the Shannon past Castleconnell and the (once famed) Falls of Doonass. This is the cause of the flooding in that area.

    The cause of the floods in Athlone and further upstream seem to arise from the hoarding and damming of Winter rains the big lakes.

    It strikes me that there should be a study undertaken on the feasibility of remodelling the turbine restriction at Ardnacrusha so that most of the flood can go straight through Ardnacrusha in some way. This may result in the cessation of electricity generation at Ardnacrusha but that may be right price to pay to alleviate all this suffering Winter after Winter.

    That, and the cessation of hoarding of Winter rains in the lakes would surely go some way to “draining the Shannon”.

  34. An Taisce has published an article on the flooding, according to which the solution must be multi-faceted and holistic:

    Here’s one paragraph from the article:

    “We need to slow down the speed with which water is moving into the Shannon and that will require change on a landscape/catchment basis. The drainage of our bogs and wetlands by Bord na Mona and through the arterial drainage scheme and various forestry programmes over the preceding decades have unquestionably exacerbated this winter’s floods.”

    I wonder what the intrepid defenders of bogcutters’ “rights” such as Luke Ming Flanagan would have to say about that.

  35. Ardnacrusha has one significant problem – its four turbine tubes can only take a maximum of 400 tonnes of water per second from the Shannon. We cannot close those tubes during winter.

    A means needs to be found to remodel Ardnacrusha so that more water can pass through it in times of flood.

    At present, the floods are delivering over 800 tonnes per second to Ardnacrusha. To protect the dam, the ESB has diverted the surplus flow down the old neglected course of the Shannon. This is the cause of the massive flooding downstream.

    The dam at Ardnacrusha was built with six large openings for turbine tubes but only four tubes were installed. One of the surplus openings is now partly used as a fish pass. The remaining opening is closed presumably by a sluice gate. If these idle openings were brought into use they could remove 200 tonnes of flood per second which is half the water which is flooding Clonlara, Castleconnell etc at present.

    The dam is also pierced by an enormous 100 foot deep boat lock. Does the ESB ever use this sluice to relieve flooding?

    There have been many expensive studies on Shannon flooding. Has there ever been a study on the feasibility of remodelling Ardnacrusha to solve the problems caused on the lower Shannon by the restricted flood flow through its four turbine tubes?

    The ESB are really going to have to step up to the mark and release a lot more information to citizens regarding the workings of its hydro stations. We need precise figures on how many MegaWatt Hours are delivered annually to the national grid. We need information on all engineering restrictions at Ardnacrusha and elsewhere. We need online realtime access to water level readings on the Shannon and all other waterways under ESB control. The Office of Public Works and the Environmental Protection Agency aleady provide the data anline for their rivers.

    We need a debate on re-engineering and renovating Ardnacrusha. This is essential if the residents of the lower Shannon are to enjoy a better quality of life.

  36. Just came across your posting by accident and must say that I found it excellent – and very perceptive!

    I have been working full time for several months now, on a conceptual engineering solution to Shannon Flooding, but still have a long way to go to satisfy my own expectations.
    I initially started with the tunnel idea but immediately realized the futility of that exercise.
    I believe I have economically solved the problem of flooding to Athlone and Limerick in concept.
    But the devil is in the detail……….and I will keep working away at the detail!

    As part of my own research, I looked at the Tay Catchment in Scotland. I thought the flood statistics for Ballantie (above Perth) may interest you.


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