A reservoir which has been left empty since water was drained away is soon set to be refilled.

The Welsh Harp Reservoir was emptied in December 2023, with a machete, Second World War munitions and even religious offerings revealed as the waters fell.

The equivalent of 400 Olympic-sized swimming pools were drained so tonnes of litter could be cleared, the reservoir’s sluices repaired and the Valve House Tower repainted.

It was originally anticipated that the reservoir would be refilled by the end of February, but the Canal & River Trust last month admitted it would take longer than expected.

The trust has now revealed that work at the reservoir is expected to be complete by the middle of April, with normal water levels restored by the end of May.

Ham & High: A look at the Welsh Harp Reservoir before its water was drainedA look at the Welsh Harp Reservoir before its water was drained (Image: Joseph Reaidi)

New nesting areas and island habitats for birds will also be created.

Ros Daniels, the Canal & River Trust’s London & South East director, explained: “Over the winter months, we’ve been carrying out a series of environmental improvements at the Welsh Harp, including creating new nesting areas in the reed beds for wetland birds, willow coppicing and removing silt from one of the ponds.

“Once the reservoir has refilled with water, with the support of the Welsh Harp Conservation Group, we plan to install 13 new island habitats for common terns, one of the species of water bird that lives on the reservoir.”

The operation has been hit by a series of delays. The reservoir was meant to be emptied in November 2023, but this did not start until December.

Then extreme weather events and the “unprecedented" number of fish meant refilling could not begin in February.

Ham & High: A clean-up event at the Welsh Harp ReservoirA clean-up event at the Welsh Harp Reservoir (Image: Canal and River Trust)

Last month, the trust many tasks still need to be carried out, including completing the fish rescue and draining, clearing silt from the front of the sluices, erecting scaffolding around the Valve Tower, cleaning and repainting the tower, mechanical work to the sluice and rods, removing the scaffolding and only then refilling the water.

Ms Daniels added: “Unfortunately the succession of winter storms and high rainfall levels we’ve experience over the winter have caused us significant delay.

“We’ve worked closely with Natural England to develop a plan to minimise the impact of this delay on the nesting birds that rely on the reservoir. 

“We’ve installed visual bird scarers, including holographic tape and decoy birds of prey, to discourage birds from nesting until the reservoir has refilled.  We expect this to happen by the end of May, but it depends on how much rain we get.”