A project to increase the capacity of Abberton Reservoir to 41,000 megalitres (9.0×109 imp gal) 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.

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.

[4] Abberton Reservoir was first filled just before the start of World War II in 1939, and the Ministry of Defence was concerned that it might be used by German seaplanes as part of a possible invasion.

Steel cables were stretched across the part of the reservoir nearest to the pumping station, since exploding mines might have damaged the building.

[8] Lancaster bombers fitted with special bouncing bombs designed by Barnes Wallis were used in these trials,[9] and military police closed the causeway whilst the practice runs took place.

The scheme was completed in 2013,[2][5] 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.

[2][15] The other major part of the project was to enable the transfer of water from the Ouse, 141 km (88 mi) distant in Norfolk,[6] to the reservoir via the Stour.

[5] The Western and Central sections of Abberton Reservoir have natural shores with common reed and willow close to the water, grading into damp grassland and cultivated fields.

The Main part originally had concrete borders, but 12 kilometres (7.5 mi) of this apron and the perimeter road were broken up in the expansion between 2010 and 2013.

[5] The new design created pools around the borders of the reservoir and allowed for creation of marshland west of the Layer de la Haye causeway.

[5] Its proximity to the coast means that Abberton may hold scarcer species like smews and long-tailed ducks, and rarities including a blue-winged teal (1996), Britain's first canvasback (1997–2001) and a lesser scaup (2004–2005).

[5] Abberton has otters, water voles and brown hares, and eight species of bats, and other vertebrates include the common lizard, grass snake and great crested newt.

Insects present include two rare weevils, Rhynchites auratus, which feeds on blackthorn, and a fungus specialist, Anthribus fasciatus.

They also burrow into river banks, which at Abberton may reduce the area available for aquatic vegetation and increase the amount of sediment entering the reservoir from the Layer Brook.

There are also significant numbers of black-tailed godwits, lapwings, coots, goldeneyes,[19] tufted ducks, pochards, pintails, wigeons and great crested grebes.

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.