Abberton Reservoir is a pumped storage freshwater reservoir in eastern England near the Essex coast, with an area of . Most of its water is pumped from the River Stour. It is the largest body of freshwater in Essex.
Constructed between 1935 and 1939, Abberton Reservoir is owned and managed by Essex and Suffolk Water, part of Northumbrian Water Group, and lies south-west of Colchester near the village of Layer de la Haye. In World War II, the reservoir was mined to deter invading seaplanes, and it was used by the RAF's No. 617 Squadron ("The Dam Busters") for practice runs for the bombing of the German dams in the Ruhr. A project to increase the capacity of Abberton Reservoir to by raising its bank height was completed in 2013, along with a new link to transfer water from Norfolk's River Ouse to the Stour.
The reservoir is important for its breeding cormorants, wintering and moulting waterfowl, and migrating birds. It is an internationally important wetland, designated as a Ramsar site, Site of Special Scientific Interest and Special Protection Area, and is listed in A Nature Conservation Review. A small part of the site is managed by the Essex Wildlife Trust.
History
Essex is one of the driest counties in the UK, The first major project to address local water needs was the establishment of the South Essex Waterworks Company in 1861, which extracted water from the underlying chalk aquifer through wells and boreholes. This supplied an area north east of London from East Ham to Grays and Brentwood. Despite the tapping of new wells, by the outbreak of World War I, the demand was outstripping supply, and eventually the need to find new sources led to the creation of a new reservoir. The reservoir was constructed between 1935 and 1939 on a site that was formerly farmland with a couple of small woods, by damming the Layer Brook, although most of its water is pumped in from the River Stour to the north east of the reservoir.
A German Heinkel bomber returning from a raid on Hornchurch airfield was shot down over Abberton on 24 August 1940. One of its crew bailed out from the burning plane and was captured; another drowned. Lancaster bombers fitted with special bouncing bombs designed by Barnes Wallis were used in these trials, and military police closed the causeway whilst the practice runs took place. The last practice flight to Abberton was a full dress rehearsal of the Ruhr attack, and took place on the night of 14 May 1943. The actual attack on the dams in Germany took place two nights later on 16 May 1943. The Edersee Dam was attacked and breached after the Möhne dam had been successfully destroyed.
In 2025, a blue plaque was installed at the reservoir commemorating Abberton Reservoir's involvement in the Dam Busters' preparations.
Expansion
The reservoir's current owners, Essex and Suffolk Water, part of the Northumbrian Water Group, recognised by 2007 that its capacity was insufficient to meet growing local demand, and initiated a £140 million project to increase the capacity to by raising its banks. The scheme was completed in 2013, and included replacing the existing link from the Stour to Abberton with new, higher capacity, pipes following a different route and extracting water at Wormingford instead of Stratford St. Mary.
The other major part of the project was to enable the transfer of water from the Ouse, distant in Norfolk, to the reservoir via the Stour.
The reservoir has a current maximum area of , and has three sections separated by the Layer Breton and Layer de la Haye causeways. The easternmost large, deep Main section, originally was enlarged to its current in 2013, the Central section covers , and the Western section is .
Protection
Abberton was designated a Special Protection Area on 5 December 1991 as a result of its over-wintering populations of golden plovers, gadwalls, shovelers and teals, and for its breeding population of cormorants. There are also significant numbers of black-tailed godwits, lapwings, coots, goldeneyes,
It is an internationally important wetland that was designated as a Ramsar site in 1981, and became a Site of Special Scientific Interest in 1988, three years after Hanningfield Reservoir received the same status.
A small part of the site is managed as a nature reserve by the Essex Wildlife Trust.
Access
thumb|Abberton Visitor Centre|alt=single-story building
The Essex Wildlife Trust has a car park and nature reserve, the Abberton Reservoir Nature Discovery Park, at the north end of the Layer de la Haye causeway. There is a visitor centre with a shop, café, toilets and play area, and three bird hides, two looking south and east over the Main section, and one in woodland. The visitor centre and reserve are open every day from 10 am–5 pm .