The Prospect Heritage Trust Inc.
© Prospect Heritage Trust Inc.
In 1869 a Commission appointed by Governor Young recommended the Upper Nepean Scheme as the best solution to Sydney’s water supply problems. The scheme involved tapping the headwaters of the Nepean River and its tributaries, the Cataract, Cordeaux and Avon Rivers.
A number of diversion weirs were built across the streams, which fed into tunnels, canals and aqueducts known as the Upper Canal, which carried the water to Prospect Reservoir. From Prospect the water was carried down the Lower Canal to a basin at Guildford, now known as Pipe Head.
The city of Sydney finally received its water after it was piped from Guildford to a service reservoir at Potts Hill and from there to Crown Street and several other reservoirs around the city. Work on the Upper Nepean Scheme began in 1880, and was finished eight years later, at a cost of two million, seventy six thousand, three hundred and thirteen pounds.
The man responsible for the design and implementation of the works was Edward Orpen Moriarty, M.A., M. Inst. C.E., Engineer-
The dam is an earth and rockfill bank with a puddled clay core. Work to repair slumps in the upstream face were carried out in 1889 and 1890, with other remedial work being done in 1899-
The Reservoir has an Outlet Tower that is connected to the Valve House by an interconnecting tunnel. The Outlet Tower has three levels of valves that draw water from the Reservoir and the Valve House has valves and meters that control and measure the flow of water.
The valves were supplied by Glenfield of Kilmarnock, Scotland and were installed in 1882. The meters were added in1907. Both buildings are gothic revival style, octagonal in shape, of English bond brick construction. Their decorative detail consists of a castellated parapet, sandstone base course and quoins and hood mouldings on window and door openings.
The Upper Canal is still bringing water to Prospect, either into the Reservoir or into the water filtration plant that opened in 1996. Approximately 80% of Sydney’s water comes by a pipeline from Warragamba Dam to the filtration plant and approximately 20% comes from the Upper Canal or from the Prospect Reservoir.
The Lower Canal closed in 1996, being replaced by an underground pipeline that now takes the water to Pipe Head at Guildford. The water in Prospect Reservoir is kept ready for emergency use by strict quality control monitoring.
The Upper and Lower Valve Houses were built in 1887 of rosy bricks with stone trim and whiter painted crenellated parapets. They are an excellent example of Colonial Architecture. Under the Upper Valve House are 3 levels of Vales that were used for drawing off water from the Reservoir.
The downstream house contains valves and meters that controlled and measured the flow of water. Glenfield of Kilmarnock supplied the valves, Scotland, and installed in 1882. The meters were added in 1907.
8 kilometres of Water Supply Canal was completed the Public Works Department in 1888 as the 3rd component of the Prospect Reservoir Works, thereby completing the Upper Nepean Scheme. Laid on a grade of 1 in 10,000, the Canal was a good example of 19th century hydraulic engineering. It included spillways, stormwater plumes and the Boothtown Aqueduct and conveyed Sydney’s water to Pipehead at Guildford.
Prospect Reservoir is no longer used as major source for Sydney’s water supply. Since the opening of the Prospect Water Filtration Plant in November 1996, most of Sydney’s water supply now comes directly from Warragamba Dam, through the filtration plant below rhe Reservoir wall and down to Guildford through the underground pipeline.