A big topic with much to cover. By necessity - at this stage - I'll simply scratch the surface.
Early Sydney's water supply was largely dependent upon the Tank Stream, so called for the grooves or "tanks" cut into its bed (reputedly an Indian sub-continental loan word as well as a fortuitously imported water storage technique). The stream is now largely buried under Sydney's concreted CBD.
Busby's bore, more or less what we would now call a tunnel, was located in the western corner of today's Centennial Park and ran to Hyde Park. See also the Lachlan Swamps.
Later water supplies were drawn from Botany, near Sydney Airport. Remains of a steam-driven pumping station can still be seen near the eastern boundary of the airport. See also Ascot Racecourse.
With Sydney's growth over time, water was drawn from further afield and major, increasingly elaborate constructions, including reservoirs, tunnels and channels were undertaken. Much of this remains in place, either in use as intended, re-purposed or as a heritage site.
The Prospect reservoir is one such early attempt to capture a larger area of rainfall and move it eastwards.
Another significant part of Sydney's water supply history is the Nepean Dam, the last and the smallest of the four dams finished early in the 20th Century to collect water from the rising lands of the Illawarra Plateau, the major, southern source of the oddly north-westerly flowing Nepean River (which later makes a curving right turn to flow east - as the Hawkesbury River - into the Pacific Ocean north of Sydney).
See also the Cataract, Avon and Cordeaux dams. These and the Nepean Dam were part of the Upper Nepean Scheme, which fed into an earlier set of weirs and other infrastructure, including the 1880's vintage Potts Hill and Prospect reservoirs. A good explanation of how the system expanded and operated may be found here.
The Nepean Dam may possibly also have been a WWII-era emergency alighting area for seaplanes. Checkout my list of Sydney and surrounding airstrips and airports.
Another dam was constructed south of Sydney after the Nepean system, at Woronora, largely serving southern Sydney.
Also worth looking into is Parramatta's water supply.
The far larger Warragamba dam
was built largely post WWII on a western tributary of the Nepean River and largely
replaces or vastly enhances this earlier system, although all remain important, and in
operation.
More can be found at the Dictionary of Sydney.
