 It was added to the New South Wales State Heritage Register on 18 November 1999.Prospect Reservoir is Sydney's largest reservoir and stores water conveyed from Warragamba Dam, the Upper Nepean Dams (Cataract, Cordeaux, Avon and Nepean) and if necessary, from the Shoalhaven Scheme, for supplying the larger component of the water distribution system of the Sydney metropolis.Located approximately 34 km west of Sydney, the reservoir is a zoned earth embankment dam, 26m high and approximately 2.2 km long, with a storage capacity of 50,200 megalitres and an open capacity of 8,870 megalitres.