Restoration of Fisheries Habitat
on the Ballinglen River
Aughrim, Co. Wicklow
Since 2020, the East Wicklow Rivers Trust (EWRT), Wicklow County Council (WCC), Inland Fisheries Ireland (IFI), and Local Authority Waters Programme (LAWPRO) have been working together in partnership to improve habitat and biodiversity for migratory fish in rivers and streams in Co. Wicklow – the ‘Wicklow Fish Barrier Mitigation Programme’. The project has also been supported by local riparian landowners and National Parks and Wildlife Service.
In 2012 Inland Fisheries Ireland completed a survey of barriers to fish migration on rivers in County Wicklow. The scale of the problem was highlighted in the Avoca Catchment which showed that approximately 50% of the entire catchment is potentially impaired (fish migration partially or fully blocked) by man-made structures. One of these is at Ballinglen Bridge on the Ballinglen River, which is located between Aughrim and Tinahely Villages.
The Ballinglen River is a tributary of the Derry Water River, which joins the Ow River to become the Aughrim River and the barrier at Ballinglen Bridge was identified as a priority for action.
The Ballinglen Bridge is a beautiful three-arched stone bridge built circa 1790. It is constructed of local shale with lime mortar and cut stone granite voussoirs. The floor bed underneath each archway of the bridge is laid with cut granite stones which are perfectly laid and grouted.
Map of Avoca catchment showing unimpeded channels in blue and impeded (due to manmade structures) in red. From the Wicklow Bridges Project Fish Passage Report by Inland Fisheries Ireland
Unfortunately however this man made structure creates a barrier to fish migration for fish species such as the Atlantic Salmon (Salmo salar), Sea Lamprey (Petromyzon marinus), River Lamprey (Lampetra fluviatilis) and the Brook Lamprey (Lampetra planeri), all of these are given strict protection under Annex II of the EU Habitats Directive, as well as the European Eel (Anguilla anguilla), which is also a species in trouble. All of these species (with the exception of Brook Lamprey) are diadromous - i.e. they travel between the sea and freshwater habitats where they spawn and a new generation begins life all over again.
When migrating over large distances in rivers they inevitably encounter barriers to free movement which, as in the case of the Ballinglen Bridge prevents them from reaching their spawning grounds in the pristine habitat upstream.
Ballinglen Bridge (pre works)
The Ballinglen Project
Recognising the built heritage of the bridge, WCC carried out all necessary heritage and archaeology studies /reports and the East Wicklow Rivers Trust received funding from the IFI Salmon & Sea Trout Rehabilitation, Conservation & Protection Fund 2021 for the project and engaged RIVUS Ecological Engineering to complete an Ecological Impact Assessment Report, an Appropriate Assessment Screening Report and to design the fish pass and lamprey/eel pass.
The Ballinglen project involves the construction of a fish pass in the Derry Water River below Ballinglen Bridge. This is a full channel width cascaded rock ramp design fish pass.
At present, a hydraulic drop of 1.20m exists at Qmean of 1.05m3/s. The length of the proposed fish pass is 46m and average width is 8m. The gradient/slope of the fish pass is 1V:33H. The fish pass will consist of 8 weir stone cross sections which will be spaced at c.5m intervals. A low-flow channel will be incorporated into each weir stone cross section and an anti-scour toe will be constructed at the end of the ramp.
In 2024 the project was given the green light to proceed and was funded under the IFI Salmon & Sea Trout Rehabilitation, Conservation & Protection Fund 2023. IFI staff completed a pre-construction fish survey and water quality monitoring has been ongoing by WCC staff. Following a competitive tender process, RIVUS Ecological Engineering were appointed to construct the rock ramp and these works are now substantially complete and we look forward to welcoming our special river inhabitants back to the Ballinglen Valley.
This project is but one small step in the restoration of river habitat for a suite of protected species and assists Ireland in meeting our commitments under the EU Water Framework and Habitats Directives.
It is also a great example of collaboration between NGOs, private enterprise and state agencies in delivering the type of projects envisaged for rivers under the EU Nature Restoration Law.
EU Water Framework Directive (WFD)
For a watercourse or waterbody to reach or maintain ‘Good’ or ‘High’ Status under the EU Water Framework two things must be addressed – both ecological quality which includes a range of biological elements, including fish community composition and age structure, and of physical elements, including significant morphological alterations (such as the construction of in-river barriers) to waterbodies which affect the hydro-morphology of the river.
In Ireland barriers to fish migration have been identified as one of the principal issues placing channels “at risk” in terms of failing to achieve good or high status as required under WFD.
