Skip to content

Gwydir Reservoirs: The safe management of high-risk reservoirs

Event organised by ICE

16 September 2021

This event has now ended

You can catch-up on details or any broadcast and downloads here.


When four legacy-mining dams in Snowdonia were found in urgent need of repair, Natural Resources Wales (NRW) had a legal duty to make them safe or suffer enforcement action. Reservoir failure posed a risk to life or serious injury for people downstream, with criminal, civil and reputational consequences for NRW.

The Gwydir Reservoirs’ scale and location required an innovative approach; employing restorative, environmentally sensitive engineering to upgrade 150-year-old embankments offering flood attenuation whilst constructing new spillways to control flows and reduce risk to life downstream.

NRW anticipated challenges working across remote sites, in one of the highest and wettest areas in Wales, with difficult ground conditions and undocumented mine workings. NRW couldn’t predict a main contractor financial collapse and later Covid19 pandemic, which left NRW facing an unprecedented battle to meet strict regulator deadlines.

The presenters will share their experience on the multi-site project, reflecting on the legislative requirements, the works carried out on the water-retaining structures and how NRW achieved high quality and safety standards during construction whilst temporarily placing the reservoirs at the greatest risk of failure. It shall conclude on how such lessons have fed into NRW’s wider reservoir portfolio and the ongoing work to maintain excellence and combat the challenges in the 21st century.

This event is co-badged with the Chartered Institution of Water and Environmental Management (CIWEM) and with the British Dam Society (BDS).

Organised with



Membership organisation to thousands of members and organisations in over 89 countries with a dedication to improving water and environmental management.

The British Dam Society

The British Dam Society

The BDS provides technical subjects relating to the planning, design, construction, maintenance, operation, safety, social and environmental aspects of dams and reservoirs.


Andrew Basford

Andrew Basford

Natural Resources Wales/Cyfoeth Naturiol Cymru

civil engineering project manager

Read more

Andrew Basford

Andrew is a civil engineering project manager working for Natural Resources Wales.

Andrew is an incorporated engineer with over 12 years’ experience in the water engineering industry. Responsible for the delivery of the Llyn Tegid project, Andrew leads the ongoing engagement with stakeholders and is focused on certification of the works by qualified civil engineer, Dr Andy Hughes appointed under the Reservoirs Act. Andrew has worked on reservoir engineering projects since 2017. 

For more information please contact:

Felicity White