The Upper Canal System, also called the Southern Railway Aqueduct and the Cataract Tunnel, is a heritage-listed operational gravity-fed aqueduct that supplies some of the potable water for Sydney, in New South Wales, Australia. The aqueduct comprises 54 kilometres (34 mi) of open canals, tunnels, and closed pipelines that connect the Upper Nepean Scheme with the Prospect Reservoir. The aqueduct is managed by the Sydney Catchment Authority on behalf of WaterNSW, an agency of the Government of New South Wales. It was listed on the New South Wales State Heritage Register on 18 November 1999.