Water Supply
Another great need of the colony after 1788 was a reliable water supply. The patterns of rainfall in Australia do not usually create perennial streams, so that conducting water from larger, distant, more reliable sources is required.
The settlement at first used a small stream flowing through its own streets, but this soon became inadequate and polluted. Heroic efforts, for the time, were made to bring water via a tunnel from the relatively far away swamps which now form Centennial Park. Later, swamps at Botany with small dams and a pumping station became the water supply for Sydney.
In the 1880s a new grand scheme was devised to derive water from the truly distant headwaters of the Nepean River some distance to the south of the city. The scheme, though bold beyond any previous water supply plan, was immensely clever in that it could be staged as needs grew. At first run-of-river water was enough but when required, storage dams could be (and were over 50 years) erected on tributaries, Cataract, Cordeaux, Avon, and then the Nepean itself. Water was diverted by weirs and tunnels and then a long aqueduct to a large reservoir just beyond the outskirts of the city at Prospect. The aqueduct comprises kilometres of open canal, long tunnels, and piped crossings of deep gorges and the pre-existing railway. Below Prospect another canal and then large above ground pipes carry the water to a smaller reservoir closer to the point of use and at that place a pumping station, at first by a buried pipeline but later by a deep tunnel, powers the connection to the existing reticulation network, until then supplied from Botany.
It had always been recognised that the ultimate water supply for Sydney would be the Warragamba River with its huge catchment area and apparently ideal dam site in a deep narrow gorge. Perhaps in 1880 the dam was beyond the wealth or technology of the society but by the 1940s as the city grew and near disastrous droughts tested the capacity of the Nepean dams, the decision was made to build the massive and high dam. Completed in 1960 the new dam integrated well into the existing scheme as a relatively short pipeline linked it to Prospect and the reticulation network.
Further enlargements of the Sydney water supply sources were made in the 1970s to tap the adjacent Shoalhaven river catchment, of comparable area to the Warragamba. Again, this was a staged scheme with at first only run-of-river water being harvested via weirs, canals and pumping stations. Later stages could have included larger storage dams on the Shoalhaven, but these have never been proceeded with and the water needs of Sydney have been throttled back by conservation rather than endless growth in supply capacity.
All towns in NSW need a reliable water supply and this is usually met by a dam or a number of dams on small local catchments. On occasions, when drought has caused the supply to fail, water has been carried in by rail tankers. However, the main purpose of large dams on inland rivers has been to supply water reliably to irrigation areas. The first major scheme was the Burrinjuck Dam on the Murrumbidgee, started in the first decade of the twentieth century though not completed for 20 years. The huge catchment and ideal dam site provide large storage capacity of water and floods of once unappreciated volumes, as well as hydro-electricity which was at the time of construction a major source of power to southern NSW and the new federal capital, Canberra, which is not very far distant. Most of the inland rivers have been regulated by weirs and dams with a large storage dam higher in the catchment to even out water availability between good and bad years.
The overwhelmingly important river diversion project in NSW is the control of the several rivers which rise in the Snowy Mountains, the only high range in the whole continent. First conceived as a much simpler hydro-electric scheme in the 1930s, by the time work began in 1948 the concept had been enlarged to not only control the headwaters of the Murrumbidgee and Murray Rivers, but to divert the flows of the Snowy River which flowed along a short course directly to the southern coast, through the mountains to supplement the water available to the Murray valley on its long course through NSW, Victoria and South Australia. On the way, falling many hundreds of metres, the water would generate large amounts of electricity, especially useful at time of peak demand. Also included in the scheme was a very large power station at Talbingo which could also act as a pumped storage to use power, generated by thermal power stations during periods of low demand, to raise water to the upper level, ready for use in the next peak.
In the early twenty-first century planning is underway to enhance this power storage capacity by a much higher lift to Tantangara Reservoir, high in the Murrumbidgee catchment, though this scheme would use surplus solar and wind power rather than deriving it from burning coal.
