Improving Fish Migration in the Lower River Shannon Catchment

The development of the Shannon Hydro-Electric Scheme at Ardnacrusha and its diversion weir in Parteen in the 1920s were important events in the creation of an independent Irish state at that time. The project was developed as a public private partnership between the Irish Free State and Siemens-Schuck­er­twerke, and several hundred German and thousands of Irish workers completed the ambitious project in under four years. Its scale and importance made it a centrepiece for Ireland’s independent national development at the time and even today it is a significant component of the country’s electricity generating capacity.

However, the development came with an envi­ron­men­tal cost. Up to the 1920s salmon ran the Shannon, Ireland’s largest river, in huge numbers, but imple­men­ta­tion of the Ardnacrusha Scheme had an immediate effect on fish migration. Initial belief that returning adult salmon would continue to use the old river channel and access the middle and upper Shannon via Parteen Weir fish pass proved wrong. It became evident that the discharge through the hydropower station attracted fish up the tailrace where there was no passage facility to the headwater at the time so for this reason, a fish lift was retrofitted in 1959. However, neither fishway meets modern best practice and do not facilitate multi-fish species passage as required by the Water Framework Directive.

CDM Smith was commissioned by Ireland’s Department of Housing, Planning and Local Government to provide expert advisory services to a Steering Group set up to improve fish migration at Parteen and Ardnacrusha in the Lower River Shannon Catchment. The Steering Group comprises public bodies and other organisations with a role in the catchment. This important project fulfilled a key objective contained in the River Basin Management Plan 2018 – 2021 for Ireland, which implements the EU Water Framework Directive. 

CDM Smith’s work for the Steering Group was led by one of Europe’s leading experts in the field, Marq Redeker, and supported by technical staff from our offices in Ireland and Germany. Marq Redeker and his team worked with the Steering Group to identify and review potential measures for the enhancement of ecological corridors and provision of free passage to migratory fish species at Ardnacrusha/Parteen and ultimately set out a series of recommended measures, including conceptual designs, for the improvement of fish migration in the Lower River Shannon Catchment.