Are Ireland’s large hydroelectric schemes sustainable?

Ireland’s hydroelectric power stations are widely considered to be a sustainable source of ‘green’ energy. But is this really true? As we approach the centenary anniversary of the opening of Ireland’s first hydroelectricity power scheme, it is time to re-evaluate the benefits and environmental impacts of these schemes. Ireland’s large hydroelectric schemes are located on the Rivers Shannon, Erne, Lee and Liffey and are operated by the Electricity Supply Board (ESB). A total of 19.8% of the island of Ireland lies upstream of the ESB’s large hydroelectric stations and these schemes have a significant influence on this vast catchment area. It has been estimated that 47.5% of the freshwater habitat available to the European eel in Ireland is located above hydropower dams and these schemes have a profound impact on the recruitment and escapement of this ‘critically endangered’ species in these catchments. Other migratory species are also affected, for example the Annex II listed Atlantic salmon; an estimated 35.5% of otherwise naturally accessible salmon habitats in Ireland lie upstream of ESB hydroelectric schemes and no salmon population upstream of these dams is reaching its conservation limit. These schemes are discussed individually below.

The Shannon scheme

The Shannon scheme was constructed in the 1920’s. Parteen Regulating Weir diverts water down a 12.5 km head-race canal to the 86 MW Ardnacrusha Hydroelectric Station. The discharge from Ardnacrusha is returned to the river channel via a 2.5 km tailrace canal, just upstream of Limerick City.

The Old River Shannon is the 17 km depleted stretch of the River Shannon from Parteen Regulating Weir to the junction with the tailrace. Although the mean annual discharge in the River Shannon at Killaloe is 186 m3 sec-1 (cumecs). The “old” river receives a compensation flow of only 10 cumecs. This approximates the natural Dry Weather Flow for this waterbody. This discharge rate is far too low and, with the exception of occasional winter flood spills, there is generally no variation in flows on this channel. By any measure this waterbody cannot meet Good Ecological Status with this level of abstraction and regulation. This stretch of river was, prior to the Shannon scheme, one of the most renowned Atlantic salmon fisheries in the world. The roar of the famous ‘falls of Doonass’ is gone (with the exception of a short reappearance during the floods of November 2009). The old River Shannon is included in the Lower River Shannon Special Area of Conservation (SAC), but is in a state of serious ecological decline. The ESB’s misguided attempts to physically remodel the river to cater for the reduced flows have been another major impact on this waterbody.

There are virtually no salmon in the vast catchment area of the River Shannon (10,400 km2 , or around 90% of the catchment) above the Shannon hydroelectric scheme. The River Shannon has an annual conservation escapement target though the Shannon scheme of 45,000 adult salmon. However, currently the numbers of salmon passing upstream through the Shannon dams are measured in hundreds – and these are supported entirely by expensive artificial restocking. The absence of a sustainable run of salmon on the River Shannon and its tributaries is a major loss of recreational opportunities and tourism revenue for the residents of the Shannon catchment.

Ardnacrusha hydroelectric station on the Lower River Shannon.
Ardnacrusha hydroelectric station on the Lower River Shannon.

The Shannon hydroelectric scheme also has a major impact on the European eel, on a catchment with an estimated 425 km2 of rich eel rearing habitat. Access for juvenile eels is blocked, and eel trap and transport programmes are inadequate.  In 2014 it was exposed that the ESB was not operating traps on the River Shannon at the peak of the elver run period. The majority of silver eels migrating down the river have to pass though the turbines at Ardnacrusha. The Shannon eel fishery is closed, and hundreds of traditional eel fishermen have been put off the river and its lakes. Sea lamprey populations have also been affected and less than 30 sea lampreys pass through the Shannon scheme each year, and these are probably accidental movements.

The River Lee Hydroelectric scheme

The construction of the River Lee hydro-electric power scheme commenced in 1953 and both Carrigadrohid (8 MW) and Inniscarra (14 MW) generating stations were commissioned in 1957. The scheme involved the creation of two reservoirs (5 and 9.3 km2 ) upstream of both generating stations. The tidal limit of the River Lee is about 14.5 km downstream of Inniscarra.

Construction of the River Lee hydroelectric scheme required the logging and subsequent flooding of approximately 60%  of the great alluvial forest of the Gearagh. This was the largest alluvial forest in Europe west of the River Rhine, and indeed the remnants of this great forest still have this status. The flooding of the Gearagh also resulted in the release of massive volumes of greenhouse gasses and the de-oxygenation of the River Lee due to the presence of large quantities of decomposing vegetation in the reservoirs during the filling of these reservoirs. Atlantic salmon stocks collapsed on the River Lee within a few years of building the scheme. Less well known are the impacts on other species such as Freshwater Pearl Mussels, eels and lampreys but are thought to be significant. Salmon stocks on the River Lee are supported by artificial restocking with smolts downstream of Inniscarra dam. In 2008 the South-Western Regional Fisheries board (now Inland Fisheries Ireland) gave themselves a, lets face it, ridiculous 50-year target for restoring salmon to the catchment.  The River Lee hydroelectric scheme has recently been featured in a film documentary highlighting the damage of the scheme to salmon and the Gearagh alluvial forest, and there is increasing awareness about the environmental (and social) impact of this scheme. In this documentary it is is noted that if water levels were reduced modestly by the ESB in Carrigadrohid reservoir much of the Gearagh alluvial forest would regenerate. It is also noted that the capacity of Carrigadrohid power station is only 8 MW.

Inniscarra dam on the River Lee.
Inniscarra dam on the River Lee.

The River Erne Hydroelectric scheme

On the River Erne two generating stations were constructed during the late 1940’s: Cathaleen’s Fall generating station at Ballyshannon (45 MW), Co Donegal and Cliff near the border with Northern Ireland (20 MW). The hydro-electric scheme involved major drainage works in the mid-catchment area, including the excavation of 600,000 m³ of earth and rock at Belleek. Assaroe Lake (2.3 km2) was created between the hydro-electric generating stations.

The development of hydroelectric stations on the Erne has had similar detrimental impact on migratory fish populations on the Erne. This impact is even more acute on the Erne as the lower station discharges just 1.5 km upstream from the Erne estuary.

In 2014 over 300,000 ‘critically endangered’ juvenile eels died below the lower power station when the ESB again clearly failed to operate an effective eel trap and transport programme.  Everyone knew that a huge run was coming. The Erne catchment could, like the Shannon and Lee, be supporting huge runs of Atlantic salmon and associated fisheries. The expansive lakes of the Erne are optimal eel habitats but eels cannot access these areas naturally, and the traditional eel fisheries are closed. The majority of silver eels – the spawning stock of a critically endangered species  – have to pass though two hydro-power stations here.

At least 336,000 juvenile eels died at Cathaleen’s Fall dam on the River Erne in Ballyshannon during April 2014.
At least 336,000 juvenile eels died at Cathaleen’s Fall dam on the River Erne in Ballyshannon during April 2014.

River Liffey hydroelectric scheme

On the River Liffey three hydro-electric generating stations were constructed during the 1930’s and 1940’s; Pollaphouca, Golden Falls and Leixlip.  These stations have a combined capacity of 38 MW. Poulaphoucha is the largest with two 15 MW generators, and there is one 4 MW generator each at Golden Falls and Leixlip.  The River Liffey scheme has again a number of serious environmental effects. Regulation of the river has lead to significant bank erosion, particularly in the 56km stretch of river between Golden falls and Lexlip. Prior to the construction of these schemes salmon were confined to the catchment area below Golden Falls, however trout could recruit downstream without having to pass though turbines and the upper catchment was also used by eels. The dam at Lexlip is a major migration barrier for salmonids, eels and lampreys and provides less power that a couple of modern wind turbines.

Concluding remarks

It is not clear why it considered acceptable in Ireland to have so few salmon passing our hydroelectric power schemes. The combined catchment area upstream of Ireland’s large hydroelectric generating stations is 16,382 km2, or 19.8% of the island of Ireland. Even before coming to the ecological costs of this it is clear that having no salmon in this vast area is a major loss of recreational opportunities and tourism revenue. Neglecting eel recruitment and closing the eel fishery has put hundreds of sustainable traditional eel fishermen out of business, while threatening the future of this species.

It is not that the ESB are doing nothing to address these issues, it is that they are not doing anything effective. For a company that provides international engineering consultancy advice and exceptional response times to problems when power lines come down, why can’t they get elver traps on the River Shannon up and running in time for the elver runs?  Well clearly they could if they wanted to. There seems to be a policy of being seen to be doing something, but achieving nothing except ensuring that hydroelectric generation continues without any interference. There is endless scientific research which seems to purposely set out out to complicate relatively simple issues (what was the PIT tag reader experiment in the Suck catchment for exactly? a PR stunt!). IFI are complicit, or worse incompetent. The obvious fish passage problems and water management issues are always avoided, the elephant in the room. There are elaborate trap and transport programmes for eels, but when investigated these are not being operated.  Both the ESB and IFI prioritise research on silver eels but neglect recruitment – therefore securing the demise of this species above Ireland’s hydroelectric schemes.  At a recent eel conference in Northern Ireland speakers from both IFI and ESB avoided the issue of recruitment, which  – lets face it – is the most important one. The latest report from the “independent scientific” committee on eels has attempted a cover-up. At the end of the day the ESB power stations operate the same as they did when they were built and there have been no compromises in relation to water management. We have no virtually salmon in these rivers, and the eel fisheries are long gone.

The ESB’s fisheries management programmes can only be judged on the results obtained, and the results could clearly be much better. There are now probably more salmon passing through Paris on the industrialised River Seine than through Killaloe on the River Shannon. Paris is 175 km inland on one of the most modified and polluted rivers in Europe, and also upstream of the Poses hydroelectric scheme. Killaloe is 30km upstream from the tide on one of Europe’s cleanest large rivers. But take the Tummel Hydro-Electric Power Scheme in Scotland. Over 7,000 salmon can pass through the fish ladder at Pitlochry dam each year, even though this dam is located on a tributary of the upper Tay catchment. It would be like having a dam in the middle reaches of the River Suck (the largest Shannon tributary) and having thousands of salmon passing at that point. Or take another Scottish River – the Beauly. This river is 20% smaller in catchment size than the River Lee but has three large hydropower stations; Kilmorack, Aigas and Beannacharn. However, around 4,000 salmon pass the second dam upstream on this system each year (Aigas dam). No salmon pass upstream at Carrigadrohid dam – the second dam upstream on the River Lee. And it will be the same in 2058 if we follow IFI’s “plan” for the next 40 years. There is clearly something wrong with the way Irish hydro stations are managed, and perhaps more importantly, regulated.

Both the ESB and IFI prioritise research on silver eels and neglect recruitment securing the demise of this species above Ireland’s hydroelectric schemes

On the Shannon the ESB  – a commercial company – are the fisheries authority and are answerable to nobody.  On the other rivers there has been a failure by state regulators to take any action. We need a licencing system for hydroelectric schemes in Ireland. Hydopower in Ireland has to be licensed and regulated, and stations that do not pass a sustainability test should not have their licences renewed. But it takes an independent film maker to highlight the problem with salmon runs on the River Lee and water management on Carrigadrohid reservoir, and propose a solution that could allow the Gearagh alluvial forest to regenerate. Likewise the only talk about reviewing fish passage and compensation flows on the Lower Shannon is coming from an independent environmentalist. This same environmentalist exposed the ESB elver kill on the River Erne and the absence of operating elver traps on the River Shannon last year. Why is this type of pressure not coming from our state agencies? The best IFI could come up in relation to the River Lee was kicking the can down the road to the 2050’s. NPWS have failed to prepare management plans for any of our Natura 2000 sites. There has been no prosecution in relation to the elver kill on the River Erne.

Hydroelectric power is now recognised as being a greater source of eel mortality than fishing, yet all the restrictions in Ireland have been placed on the independent traditional eel fishermen. It is business as usual at the ESB’s hydroelectric power stations, but hundreds of traditional eel fishermen have been put off the lakes of Ireland without compensation. The rich lakes of the Shannon and Erne catchments could support a productive and sustainable eel fishery to the benefit of local communities and the European eel. It it is difficult to see how the record elver run of 2014 could possibly have been managed worse by the ESB, with a failure to get elver traps operating on the Shannon and a major elver kill on the Erne. In the UK, the Environmental Agency see addressing non-fishery sources of eel mortality – such as hydropower – as being their highest priority, while seeking to maintain a sustainable and economically viable eel fishery. In Ireland we did the opposite of this and just banned eel fishing and did almost nothing else to help the European eel. Following the designation of the Lower River Shannon SAC there has been no review of generation and water management protocols to assess whether there is a better and more sustainable way to manage this scheme. There clearly is  – the current compensation flow was set in the 1930’s.

Dam removal in Ireland – as extreme as this may sound now – will be on the cards in the coming decades. As is happening in the USA, there will be growing pressure in Ireland to remove dams that are not operated sustainably. ESB claim that their stations “operate to the highest possible environmental standards” and also claim that “all of their activities are regulated and audited on a regular basis”. However, how can this be true when there is no licencing system for hydro schemes in Ireland? Their stations may comply with local authority discharge licences for minor waste water emissions, and they probably have a few recycling bins. But this is, of course, not even starting to operate to the environmental standards that are required to run sustainable hydroelectric power schemes.

2 Thoughts

  1. I do not think they are sustainable . The irish wind energy association announced record wind generation of 2882 MW , at one point on 24/12/16. The hydro stations e g Leixlip can only develop up to 4 MW. It should be decommissioned and the river restored.

    Sent from my iPhone


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