Stretching for 1,350 metres, the embankments at Wilstone Reservoir are one of the longest of the 71 major reservoirs in our care.
The project
The project, estimated to cost £6 million, has started this week 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 May.
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.
An important place
Ros Daniels, our London & South East director, explains: “Wilstone Reservoir provides an important place for water storage to feed the Grand Union Canal and has also become a popular site for angling, walking and bird watching.
“This winter we’ll begin a programme of essential maintenance work to strengthen the reservoir’s embankments, securing it for the future. These are statutory safety works required under the Reservoir Act.
“To minimise disruption, the reservoir won’t be drained during the works, but the water level will be lowered by 0.5 metres below capacity. The reservoir will continue to supply water to the canal, and the water level in the reservoir will slowly reduce throughout the summer, as usual. Our engineering project team will use land-based equipment to carry out the works and, to minimise disruption, will include a silent piling machine.
“Unfortunately, the nature of the work will mean that the reservoir’s footpaths and car park will need to be temporarily closed, as well as some local roads for short periods of time. It won’t be possible to fish at the reservoir during the main construction element of the works from May 2025 to March 2026.
“The reservoir is an important wildlife site and we’ll be making a number of habitat improvements to the reed beds, as well as replacing nine small and medium-sized trees which unfortunately will have to be removed in order to carry out the works. We’ll also have to coppice a section of hedgerow.”
