Largely taking its water from the River Stour, Abberton Reservoir is the largest in Essex. But as well as being an important source of fresh water for North Essex residents, it’s also a wetland site managed by Essex Wildlife Trust. The location is a key overwintering ground for migratory birds. The damp ground hosts lapwing, curlew and golden plover and where the grass is better you’ll see wild geese. Other birds that are commonly spotted include grebe, coot, swan and wigeon populations.
An estimated 40,000 birds come each year, attracted by the shallow waters at the edge of the reservoir where they can peck about in the mud. There’s also a breeding colony of cormorants, unusual as they nest in inland trees rather than on the more common coastal cliff ledge sites. There are plenty of footpaths in the vicinity as well as a well-stocked visitor centre. You can’t quite circumnavigate the reservoir but you’ll get a close look at the water in many places.
But this tranquil place hides a chilling secret. During the war, Abberton was one of the practice locations used by RAF 617 Squadron, more famously known as the Dambusters. Preparations were intensive, with emphasis on low flying and simulated night flights. Though participating pilots didn’t know what the target of Operation Chastise was going to be, the reservoir location offered some vital clues. The Layer Causeway would have simulated a dam and was closed to passing traffic while the planes were overhead. But the reservoir, finished just a short while before war broke out, was itself a target.
The Ministry of Defence was concerned that Abberton could be used as a landing site for seaplanes and placed 312 mines across the reservoir. They were held in place with steel cables attached to concrete blocks. At the end of the war, most were exploded; soldiers were ordered to fire at them from the banks of the reservoir. Some, however, were holed and sank. A prolonged period of dry weather in the late 1980s led to 22 of these mines being exposed on the reservoir’s banks and the army were called in. Seven still had some explosives intact and were blown up. Since then, a specialist diving unit has carried out a thorough survey and the reservoir is now officially clear.