The project, estimated to cost £6 million, will start in mid-January with site preparations. Work to install two thousand 11-metre-long steel sheet piles into the reservoir’s two 200-year old embankments, will begin in June. Stretching for 1,350 metres, the embankments at Wilstone Reservoir are one of the longest of the 71 major reservoirs in the Trust’s care.
Project update May 2025
Wilstone Reservoir embankment strengthening works update
Work to create a temporary vehicle access track has begun.
We expect to start the piling work at the end of June, starting at the north east corner of the reservoir. This will require closure of the footpath along the top of the reservoir dam. Pedestrians will be diverted through the field next to the reservoir, maintaining access to the farm shop and café.
We plan to close the Wilstone Reservoir car park in early September for around four months, while we complete the piling work and build a new footpath along the top of the dam.
We will also need to temporarily close the road next to the car park for a short amount of time, while work is taking place on the reservoir dam. A traffic diversion will be in place, but the farm shop and café will remain accessible. More details of the dates and duration of the closure will be published shortly.
The piling work is expected to take around five months.
Explaining the timing of the works – working with nature
The work to strengthen the embankments at Wilstone Reservoir is taking place over the summer months so we can work with the natural trend of the reservoir’s water levels. It’s a groundwater-fed reservoir, rather than rainwater-fed, and the early months of the year are when it naturally refills.
We expect the reservoir’s level to have dropped by the autumn, following the drier summer months and increased boat movements on the Grand Union Canal. In the autumn we plan to carry out works to the outfall syphon that require lower water levels.
The piling will be completed by Christmas, allowing the reservoir to naturally refill as usual in the new year.
Project update March 2025
Wilstone Reservoir Embankment Strengthening Works Update
Vegetation management work has been completed, required to create access space for our construction plant and materials. Work to create a temporary vehicle access track is expected to get underway after Easter and is likely to take several weeks. The main piling work is planned to begin in late May. Ahead of this phase, we’ll need to close the footpaths and car park at Wilstone Reservoir. We’ll issue another update ahead of this phase of the project confirming the exact date. Footpath diversions will be in place.
Local road closures won’t be needed until later in the summer. We’ll publish details of these as soon as possible, and the closures will be as short as possible.
The reservoir’s water level is currently at the level required to facilitate the works.
Wilstone Reservoir
Wilstone Reservoir is part of the Tring Reservoirs Nature Reserve Site of Special Scientific Interest (SSSI). Originally built to supply water to the Grand Union Canal, the reservoirs are now also one of the best birdwatching spots in southern England. The four individual reservoirs in the Tring Reservoirs Nature Reserve are Startop’s End, Marsworth, Tringford and Wilstone. The Herts & Middlesex Wildlife Trust leases and manages the Tring Reservoirs, and we maintain operational responsibilities.
Built in 1802 to supply water to the Wendover Arm of the Grand Union Canal, Wilstone Reservoir is the largest of the four reservoirs at 119 acres (48 hectares). It is up to 18 feet (5.5 metres) deep and has the capacity to hold over one million mega litres of water, the equivalent of over 300,000 Olympic sized swimming pools. The reservoir has two five-metre wide embankments stretching for a total of 1,350 metres and ranging in height from two to eight metres.
