The groundwater at Rome was notoriously unpalatable, and water from the Tiber was unsafe to drink. Aqua Appia, Rome’s first aqueduct (312 BC) was commissioned by the censor Appius Claudius Caecus as a publicly funded major project.

By the late 3rd century AD, Roman aqueducts supplied Rome with water by a combined conduit length of 800 kilometres, of which only 47 km were carried above ground level by the familiar masonry supports. They supplied around 1 million cubic metres (ie 10,000 GigaLitres) a day; enough to supply a modern city of population of 10 million. The longest was the Constantinople (Turkey) around 500 km. Gradients for Roman Aqueduct were 1:4800 and typically around a metre wide and deep with a flow rate estimated to be about 35,000 m3 /day (or 350GL/day) depending on the season .

With the fall of the Roman Empire, some aqueducts were deliberately cut by enemies but many more fell into disuse through lack of organized maintenance. Their failure had an impact on the population of cities; Rome declined from its high of over 1 million people in the Imperial era to as low as 30,000 in the medieval era. 

The New Bradfield Scheme is very similar length, capacity and function to the Roman aqueducts being totally gravity fed. With an estimated fall of 1:5000, 100m from Hell’s Gate over a distance of 500 km to the Lakes Buchanan and Galilee Storages, a wider, lined channel could easily provide the 20,000GL per annum. Harvesting the flow from streams along would be possible, or desirable helping to reduce flooding lower in the catchments and leading to potentially greater harvest rates. Spillways would dump the excess if the water level got too high.

As Sir Humphrey Appleby said about public projects (‘Yes, Minister’): “Anything is possible for government, so long as it isn’t the first time.” The Roman Empire has done a similar-sized gravity-fed aqueduct system 2000 years ago.

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The experts say it can’t be done, but a close look at the elevations of the sources, storages and destinations for the Bradfield Scheme says otherwise.

The ideal gradient for an open gravity-fed irrigation channel is 1:5000 or 100m per 500 km. Any flatter and the flow slows and steeper risks damage. This is the typical gradient for the Roman aqueduct system totaling over almost 1000 km delivering 10,000 GigaLitres of fresh water to Rome per day.

In an eastern Bradfield Scheme, the elevation goes from 430m at Niall near the Burdekin River to Lake Buchanan over the 500km to the main storage at 340m at Lake Buchanan and 280m on Lake Galilee. This is an average gradient of 1:5000.

The water could potentially be distributed throughout the whole of the fertile black soil plains area of Central West Queensland, from Barcaldine at 267m and Aramac at 226m, to Longreach and Richmond at around 200m, as far as Julia Creek at 132m about 500 km from Barcaldine (light blue polygon). Again 1:5000.

The topography starts to rise towards Hughenden at 318m and Blackall 284m and so would set the furthest extent for a gravity-fed supply. However, the land continues to fall towards Birdsville 48m and Innaminika 16m and so could continue to be fed in a south-western direction.

The Tully Falls near Cairns at 670m elevation and Herbert River are viable sources of gravity-fed inflow to the scheme.

The black soil plains of Central West Queensland currently support mainly low intensity grazing due to the irregular water availability. However, they are well located to supply communities to the north, south, east and west with higher value agricultural products, including irrigated cotton, wheat, and horticultural products. This would be enabled by a well established infrastructure of rail and road connections.

Water from the scheme would also augment town water supplies, many of which are under extreme pressure, where the drought-hit town of Ilfracombe has even imported a temporary desalination plant.

Water from the eastern portion of the scheme may largely flow to the Muttaburra, Aramac, Longreach and Barcaldine area, while from the western portion of the scheme fed by Gulf rivers may supplement areas such as Richmond and Julia Creek.

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Above is a schematic diagram of a gravity-fed mini-Bradfield Scheme transporting water from the coastal rivers via a levy/pipeline combination (blue) to the storage and distribution lakes on the Great Dividing Range (green).

The levy would accumulate water from the Burdekin River at Hell’s Gate (note the dam would not be needed) and acquire the additional water en route at the Basalt, Campaspe and Cape Rivers (purple). These are headwater collections and so would not impact the regular flows greatly, and help to mitigate flood flows downstream.

The storage lakes of Lake Buchanan and Lake Galilee are currently dry salt lakes whose capacity would be greatly expanded by dams at a few strategic locations. The lakes are uniquely positioned at intermediate elevations on the Great Dividing Range allowing stored water to be gravity fed to the destinations.

From the storage lakes, channels or pipelines would distribute the water where and when needed – to industrial uses east of the Divide such as the Adani Mine, and to new irrigation areas west of the Divide around Muttaburra, Aramac, Barcaldine and Longreach.

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