Ardleigh Reservoir is a 49-hectare (120-acre) lake near Colchester in Essex, England constructed in the valley of the Salary Brook.

A draft Water Order was made and a public inquiry was held in December 1969.

The South Essex Waterworks Company built a water intake upstream of the barrage, a pumping station at Brantham, and a pipeline to the new Ardleigh reservoir.

[2] The treatment plant has included Dissolved Air Flotation (DAF), Granular Activated Carbon (GAC) filters, ozone dosing, Rapid Gravity Filters (RGF) and Actiflo technology.

[4] In 2011 SRC Aggregates planned to remove 4 million tonnes of gravel from a site adjacent to the Ardleigh reservoir to eventually create a new reservoir of 1.8 million cubic metres (64×10^6 cu ft) capacity.