Llyn Brân

Llyn Brân is located in Denbighshire, just outside Bylchau, on the B5401 between Denbigh and Pentrefoelas. It is a raised natural lake, impounded by a small concrete dam which was built around 1899.

The reservoir was used to supply water to the North Wales Hospital in Denbigh. But since the hospital closed in 1995 Llyn Brân is no longer needed as a drinking water reservoir. That’s why we’re restoring the lake to how it was before the dam was built. But this work will take time. We’ve done all we can, and now we’re letting mother nature do the rest.

We’ve lowered the water back to its natural level, removed the dam and created a new channel to reconnect the lake to the river.

Now the lake is at its natural level, we’re allowing the shorelines to dry out and revegetate naturally. Over time, these areas will re-naturalise and become green but in some areas we’ve helped this process along by covering the area with vegetated matting.

As it will take a few years for the shorelines to flourish, Llyn Brân may not look at it’s best at the moment, but when the area has recovered and re-established, the lake will once again blend into this remarkable landscape. We will continue to monitor the site as it returns to nature, and we hope, through our careful restoration work, that Llyn Brân will eventually become a Special Area of Conservation.

We started the work in May 2022 and finished in October 2022.

Ongoing Ecological monitoring of the lake will continue until winter 2024.

What we’ve done?

Over the summer months of 2022 we:

  • Constructed a temporary access track to the site
  • The reservoir was then lowered by approximately 2.4m, taking it back to the natural lake level. This was done using a system of syphons and pumps to remove the water
  • Removed the dam at Llyn Brân. The construction work involved complete removal of the dam structure, ecological enhancements and shoreline restoration. The work has reduced the surface area of the lake of approximately half (123,500m² to 61,500m²)
  • Demolished ancillary building and associated structure located at the north eastern area of the reservoir. All building waste was removed for disposal off-site.
  • Exposed sections of pipework was removed and disposed of off-site. Buried pipework was sealed and filled by grouting
  • New roadside fencing was installed along the south side of the A543 at the north end of the reservoir
  • Installed a layer of stone to protect the soil surface from erosion.
  • Remediation works around the shoreline and downstream watercourse to complete the works, with natural coir matting placed around the margins.

Take a look at how the work was done:-


Protection of the environment has always been at the forefront of this project.

We worked closely with Natural Resources Wales (NRW) and specialist environmental consultants throughout this scheme. Detailed ecological surveys, assessments and mitigations were made to ensure the work does not cause a negative impact to the environment.

Dam removal is widely recognised as being beneficial to the environment and NRW is supportive of the work we are doing. By removing the dam structure at Llyn Brân, we will see an improvement in the local biodiversity of the area. In fact. the work at Llyn Brân will result in the site becoming a Special Area of Conservation (SAC).

We are also turning Llyn Anafon reservoir near Llanfairfechan back to a natural lake. As a compensatory measure, some rare plants from Anafon will be transferred to Llyn Brân to increase the resilience of the species.

After the work

Immediately following the lowering of the water, the edges around the lake may look muddy as silt becomes exposed. These areas will be covered with natural seeded matting, which will start to grow throughout spring / summer 2023. As the mats grow and establish, the site will look begin to re-naturalise. The matting will not cover the whole area of the exposed edges and will seed naturally over time. Pre-vegetated matting was installed in some areas which will form part of the habitat restoration for the water vole population at Brân.

Llyn Brân Artist’s impression

Artist’s impression of how Llyn Brân will look once the natural seeding matting grows and re-naturalises the water’s edge.