Annacotty

A barrier is anything that might prevent a fish from passing, migrating or may slow it down on the way up or down a river. Barriers alter river habitats, affecting the physical character and water content. Physical barriers can be natural or man-made features and can include weirs, bridges, waterfalls, culverts, fords, dams, sluices and ramps. Inland Fisheries Ireland has been building a national inventory of barriers under the National Barriers Programme since 2017. An online dashboard by IFI has identified over 5,250 barriers at locations across Ireland.  

The ultimate goal of this pilot project is to improve fish passage at Annacotty Weir on the River Mulkear, helping migration of fish both up and downstream. This project is also a pilot that involves a team of multi-disciplinary panel of internal and external experts. The approach will inform similar future mitigation projects undertaken as part of a national mitigation programme.

A weir is a river barrier aimed at regulating flow conditions, altering water levels, intercepting sediment or reducing the channel slope of a watercourse. Water often flows freely over their top except in low flow conditions. Weirs come in many shapes and sizes but often have a height of less than 5 meters. 

Annacotty Weir was used in the past to divert water to the Mill as a source of power generation but the current weir is a serious barrier to lamprey, salmon and trout.

To progress the project an Interagency Group for Annacotty Fish Passage Project has been set-up, which includes representatives from Inland Fisheries Ireland, the Department of the Environment, Climate and Communications, the Department of Housing, Local Government and Heritage, Limerick City and County Council, the Office of Public Works (OPW), the National Parks and Wildlife Service (NPWS), the Local Authority Waters Programme (LAWPRO) and the ESB.

This new division at IFI aims to improve river hydromorphology and connectivity in Irish catchments by strategically targeting priority barriers to fish passage and structures degrading river form, flow and function.  This will be done through a targeted programme on the implementation of mitigation. 

Government funding of €110 million for this programme has been made available to remove, mitigate and where possible lessen the ecological impact of river barriers on migrating and resident fish species.

Approximately 7,000 of the 73,000 potential barriers identified nationally will require removal or mitigation. Over the first phase of the programme (2014 -2017) it is expected that 257 barriers will be progressed. 

Annacotty Weir has been identified as a significant barrier to the free movement of fish. Barriers to migration can block or delay migrating fish populations and may lead to increased mortality through diseases and predation. Delays in smolt migration may also affect their survival when they enter the sea. 

Annacotty Weir is a high impact barrier to the migration of adult salmon and sea trout and a complete barrier to the migration of sea and river lamprey. To these anadromous species, human-made barriers are considered one of the most pressing threats to existing populations.

Barrier mitigation is the modification or removal of instream manmade structures to help migrating fish, insects and animals. The goal of barrier mitigation is to return the river to a more natural condition.

Across the European Union (EU), fragmentation of river habitats by barriers is one of five main causes of biodiversity loss. Barriers modify the river habitat or hydromorphology which considers the physical character and water content of water bodies. Hydromorphological modification is one of the primary reasons why rivers fail to achieve ‘good ecological status’ based on standards of the EU Water Framework Directive (WFD). 

River continuity is a key aspect of good ecological status. Removal or adaptation of barriers is part of the measures necessary to fulfil the legal obligations under the WFD. River continuity is necessary also to achieve the objectives of other EU legislation, the Habitats Directive protects the Atlantic salmon, river and sea lamprey which need to migrate between the sea and freshwater. The European eel, protected by the Eel Regulation, also needs river continuity to survive. 

The removal of weirs and dams is considered best practice as it restores the natural flows and conditions of rivers, as well as the benefits they provide. Removal opens fish migration routes and releases trapped sediment and nutrients that maintain habitat health. Therefore, it is important to prioritise removal over fish pass provision where possible. Fish passes should be a last resort as they do not adequately address the problems of habitat connectivity/ degradation and may not adequately provide passage for all fish species. 

Weirs fragment and disrupt the connectivity of the natural river processes. They can prevent sediment movement, water flow and habitat formation for a wide range of flora and fauna such as salmon, lamprey, freshwater pearl mussel and macro invertebrates. Below is a graphic highlighting the various problems fish species have with a structure like Annacotty weir.

Annacotty Weir has been altered on several occasions in the past. In the earliest Cassini maps of Ireland, there are only ‘waterfalls’ marked at Annacotty. A weir in a different configuration is present in the early 1900s maps. The orientation of the weir was altered by the OPW in the mid-1990s to the present arrangement and a Denil fish pass was constructed. 

Mulkear LIFE (2009-2014), an EU Commission-funded project, focused on salmon, sea lamprey and otter in the Mulkear catchment. As part of this project, sea lamprey passage was improved at Annacotty weir through the addition of a plastic egg cup- like climbing substrate (lamprey tiles) attached to the weir face. 

Temporary works require agreement with all stakeholders. As this site is within a Special Area of Conservation this can be a difficult task as all relevant legislation needed to be followed. 

Temporary solutions should also be quick to install, robust, low maintenance and should represent good value for money. A temporary solution should facilitate the migration of all fish species of interest, and it should be able to operate continuously and effectively during the construction phase of the permanent structure. The temporary solution should to cover the lengthy timescale that barrier mitigation processes can take.

Low river flows below the 95th percentile are required to put in place works to proceed. Unfortunately, due to the heavy rain in Summer 2024 works could not proceed under health and safety requirements with proposed temporary measure of refurbishment of the Denil fish pass and to restore the lamprey tile matts on the weir face. 

A Denil Fish Pass was constructed as it was the standard at the time. Current standards require consideration of all species and their differing swimming abilities.

Lamprey Tiles were installed during the Mulkear LIFE project, these have degraded over time and need continuous maintenance. It should be noted that the lamprey tiles only improve passage for sea lamprey and not river lamprey.

The work was carried out under the OPW’s Ballymackeogh certified drainage scheme. The weir unfortunately was in a state of neglect and needed to be refurbished.

In the first instances, all the options will be assessed by the consultants in terms of the environmental and engineering design implications. 

Depending on stakeholder feedback and the results of outstanding environmental and site investigation data, a preferred option will be put forward by the multi-disciplinary panel of experts. An option report will document the process with a multi criteria decision matrix scoring elements of each option. The option with the highest score will become the preferred option. 

A planning application will be submitted for the preferred option and the competent authority will make a decision on it. 

A matrix is to be used to score elements of each option. Elements taken into account include the passage of all fish species, technical issues, flood risk, amenity value, impact on habitats and nature, visual aesthetic, heritage and archaeology.

An online feedback form for the public consultation is available to contribute to the process. A stakeholder feedback report with recommendations will be used to inform the decision. 

There are currently eight options available. These are: 

• Option A – Partial Removal of the Weir
• Option B – Complete Removal of the Weir
• Option C – Refurbishment of Existing Fish Ladder
• Option D – Lowering of the Existing Weir in conjunction with other fish passes
• Option E – Installation of Rock Ramp Fish Pass Downstream of the Weir
• Option F – Installation of Rock Ramp Fish Pass Upstream of the Weir
• Option G – Bypass Channel
• Option H – Retain Existing

Inland Fisheries Ireland secured funding under the Salmon and Sea Trout Rehabilitation, Conservation and Protection Fund for the Annacotty Fish passage project. This is being used to deliver the technical, engineering, stakeholder engagement and planning elements of the Annacotty Weir project.

Recently government funding of €110 million has been approved for a programme to remove, mitigate and where possible lessen the ecological impact of river barriers on migrating and resident fish species. This is critically important for Atlantic salmon, European eels and lamprey. Over the life of the programme, it is expected that 257 barriers will be mitigated. This funding will focus on mitigating structures in rivers, including bridge aprons, culverts, sluices, and weirs which can interfere with natural river processes including fish movements and migration. 

Tender documents for this project were published on the eTender website on the 20th of January 2023, with a consultant being awarded the project on the 25th of April 2023. Since this essential surveys and reports have been completed including an Underwater Archaeology Report, A Fresh Water Pearl Mussel Survey, Topographical Survey, Appropriate Assessment Screening Report, Hydrology Report, Hydraulic Report, Architectural Heritage Assessment, Archaeological Impact Assessment, ect.

Eight options have now been developed with this information which IFI are now seeking stakeholders feedback on to inform the process.

A new division since May 2024 has also been established with IFI to specifically progress barrier removal. This is known as the national barrier mitigation division and resourcing of the division is ongoing for dedicated staff to work on projects such as Annacotty.

The EU Biodiversity Strategy 2030 aims to make 25,000 km of rivers free flowing by 2030. In line with this strategy Ireland’s 4th National Biodiversity Action Plan 2023–2030 has a target that requires the restoration of 300 km of rivers to a free-flowing state. 

The EU Nature Restoration Law is a new regulation by the European Commission to restore at least 20% of the EU’s land and sea areas by 2030 and repair all ecosystems in need of restoration by 2050.

The EU Water Framework Directive (2000/60/EC) requires all Member States to protect and improve water quality in all waters so that good ecological status is achieved by 2027. Ireland’s 3rd River Bain Management Plan is called the Water Action Plan 2024. It specifically mentions Annacotty Weir as a pilot project in the programme for mitigation.

The EU Habitats Directive (92/43/EEC) conservation objectives for the Lower River Shannon SAC, aim to increase river accessibility for migratory species such as Atlantic salmon and lamprey.

The EU Eel Regulation (1100/2007) requires EU countries to implement recovery measures for European eel populations. The Annacotty fish passage project will help to achieve this goal. 

A minimal maintenance regime is to be designed by the consultant for the preferred option. Inherently, some design options require less maintenance. If works proceed a contractor will be responsible for a defect liability period as part of the contract terms and the option of a maintenance contract will be examined.

A planning application will be submitted for the preferred option and the competent authority will make a decision on it. 

A matrix is to be used to score elements of each option. Elements taken into account include the passage of all fish species, technical issues, flood risk, amenity value, impact on habitats and nature, visual aesthetic, heritage and archaeology.

An online feedback form for the public consultation is available to contribute to the process. A stakeholder feedback report with recommendations will be used to inform the decision. 

Stakeholder feedback is now open to inform the process and will be complete in Q1 2025. The project consultant will then collect the remaining environmental surveys, site investigation data and produce the options report to identify the emerging preferred option in Q2 to Q3 2025. A planning application submission will follow and subject to receipt of a granting of permission a tendering process for the construction contract will begin. The earliest window for construction to commence is in Q3 2026 that is subject to the instream window for construction works giving a final handover & commissioning phase of Q4 2026.

The Technical Expert Group for Salmon (TEGOS) uses scientific indices like fish counter data and rod catch data to determine if there will be a harvestable surplus in the river the following year. TEGOS determined the catch and release designation of Rivers like the Mulkear.

Wild birds such as cormorants are currently a qualifying Interests for the River Shannon and River Fergus Estuaries Special Protected Area (SPA). This gives them protected status under the EU Birds Directive on the Mulkear SPA area. 

Dace is a cyprinid fish with a European-wide distribution but are not native to Ireland. It was first introduced to the Munster Blackwater in 1889 and were first reported below Annacotty Weir in the 1990s. An ESB survey recorded dace upstream of Annacotty Weir in 2001 and again at Barrington’s Bridge in 2010 and in 2013. Dace can already traverse Annacotty Weir. Any impact of weir alterations on the dace population will be assessed as part of the options report.

Almost the entire Mulkear catchment, including the River at Annacotty, is within the Lower River Shannon Special Area of Conservation (SAC). SACs protect important environments and species as listed in the EU Habitats Directive.

Investigation have been undertaken; it is theorised that a portion of lamprey attempted to breach the millrace sluice gate during high water levels and once the levels dropped the lamprey were trapped.

With mitigation of the weir, a preferential flow of attraction will be established, reducing the likelihood of similar incidents in the future. 

The Mill Building (RPS1614, NIAH Reg. No. 21900605) is a recorded protected structure and the associated Mill infrastructure is to be protected in all options. The weir is unfortunately causing a blockage to fish species in its current form. The weir has been heavily modified in the 1990’s and is no longer the same weir that was in place from the past. An Architectural Conservation Impact Assessment Report will establish the impact in detail of the proposed option.

Refurbishing of the existing weir fish passage requires significant planning and environmental legislation be followed. The time and work involved in getting this approval would be the similar to the current project work of examining all options. 

Unfortunately, a refurbished Denil fish passage will not allow all fish species upstream of it. Steps on the weir structure would be at too step a gradient to allow all fish upstream. River fragmentation will remain in this scenario which goes against the EU laws. 

Rock ramps upstream and downstream of the weir are being examined as two sperate options as part of this project. Stakeholder feedback on these options is welcomed.

Ballyclough Weir is no longer a barrier to fish passage due to is breaching in 2013. Please see the below photo. Annacotty Weir is a significant priority barrier on the Mulkear River due to its location at the downstream end of the catchment, its height and full channel barrier blockage. It significantly impedes the migration of adult salmon and sea trout and completely blocks sea and river lamprey. Freshwater barriers can block or delay migrating fish, leading to increased mortality.

A detailed calibrated hydraulic model by the project consultant is to be developed on the preferred option to ensure there is no increased flood risk. See below photo of the Annacotty Weir at a time of flood with the weir drowned out and giving no flood protection to properties downstream of it.

The Department of Housing, Local Government, and Heritage (DHLGH) is working on this project along with the NPWS, EPA, IFI, OPW, ESB, Waterways Ireland, Shannon Fisheries Partnership, Irish Water, LAWPRO, Salmon Watch Ireland and Academic involved in the steering group. See below details for further information on the project timelines.