Selset Reservoir will be closed to the public until the end of the year while a £12million project to improve the dam wall takes place.
The scheme is expected to get under way in June and run until December, subject to approval from Durham County Council.
The work, by Northumbrian Water, will involve increasing the resilience of the dam wall, meaning water levels in the reservoir will have to be reduced.
A spokesman said for safety reasons it means the site will be closed to the public.
However, this year has seen the re-opening of most of neighbouring Grassholme, with the exception of the dam wall and a small part of the north shore, as work on that reservoir moves into its final stage.
This is due to be completed in 2022.
The re-opening brings Grassholme’s new angling facilities into use – which Northumbria Water says will make the sport even more accessible for visitors.
Northumbrian Water’s project manager Mike Ciaraldi said: “This work will see us improve the resilience of the dam wall at Selset Reservoir.
“With the majority of Grassholme Waterside Park once again open to the public, with its new leisure amenities, this is a good time to carry out this work with minimal disruption to those who enjoy spending time in this part of Teesdale.
“We would urge people to respect the closure of the site and take the opportunity to visit Grassholme, or one of our other Teesdale reservoirs, while this work is being carried out, and our leisure team look forward to welcoming them back to Selset later in the year.”
Updates on the project will be posted at www.nwlcommunityportal.co.uk.
