September 1960: Australia's Snowy Mountains hydroelectric scheme

Eastern Australia receives around 32 per cent of its renewable energy from a hydroelectricity scheme that took 25 years to build by 100,000 workers from 30 countries.

Developed for energy and irrigation, the Snowy Mountains Scheme consists of nine power stations, 16 major dams, 80km of aqueducts, 145km of interconnected tunnels and is run by Snowy Hydro, which overseas more than 5,500MW of generating capacity across New South Wales, Victoria and South Australia.

In September 1960, The Engineer ran an update on progress of the mega-project, which sought to fulfil nineteenth century ambitions of diverting water from the Murray, Murrumbidgee, Snowy and Tumut rivers to drought-proof parts of New South Wales (NSW) and Victoria. “Construction of the vast complex of reservoirs, tunnels and power stations in South Eastern Australia known as the Snowy Mountains Scheme has been in progress for about a decade,” said The Engineer. “Power generation and irrigation are both important aspects of the scheme, and the aim of the design has been to store the waters of the four main rivers which rise in the area of the scheme, at a high level, at the same time redistributing the flow amongst them, such that substantial additional quantities of water are diverted northwards in the Murray and Murrumbidgee (through its tributary the Tumut) to the regions where irrigation is needed. Because of this dual function, power is generated at low load factors.”

According to the report, the key storage for the whole scheme was Lake Eucumbene in the Snowy catchment, with a gross capacity of 3,860,000-acre feet and a top water level 3822ft above sea level.

The Engineer said: “Tantangara reservoir will store the headwaters of the Murrumbidgee and divert them into Lake Eucumbene. Utilisation of water flowing from Lake Eucumbene can then proceed in two ways. First, by diversion through the tunnel to Tumut Pond reservoir; that is, to the catchment of the Tumut River, where a straightforward chain of reservoirs and power stations stretched out along the Tumut controls its flow for irrigation further north as required, and generates power in… four stages. Tooma reservoir and tunnel are an addition to this system, conveniently available from the Murray catchment.

The second route from Eucumbene reservoir was seen as more complicated. The 15 miles long Eucumbene-Snowy tunnel was designed to allow flow in both directions, facilitating redistribution of the Snowy catchment’s run-off to either the Murray or Tumut, as circumstances dictated.

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“A high-level chain of power stations starting at Kosciuszko reservoir will discharge into Island Bend reservoir which is situated at this redistribution point,” said The Engineer. “Furthermore, run-off collected from lower levels in the Snowy catchment will accumulate in Jindabyne reservoir (capacity 250,000 acre feet, top water level 3000ft above sea level) and will be pumped into the Murray system.

“The Jindabyne pumping station will utilise off-peak energy, since it will draw from a large reservoir; its capacity has not yet been determined. Diversion from the ‘redistribution point’ to the Murray catchment will follow a 9.5-mile tunnel under the Great Dividing Range, to Geehi reservoir, the three reservoirs at Eucumbene, Island Bend and Geehi all at substantially the same level (i.e. in the range 3600-4000ft above sea level), thus being an indispensable part of the arrangements for redistribution of flow. From Geehi reservoir there will then be a straightforward chain of power stations along the Murray, ending in a tail-race pond below the last station.”

The entire scheme would provide nearly 2,000,000-acre feet of water annually in the Murray and Hurrumbidgee, which would allow about 1000 square miles to be cultivated at an annual turnover of £30,000,000 . The installed capacity was designed to be around 2500MW and the annual energy output 5500 x I0⁶kWh, or an overall load factor of about 25 per cent. The total cost of the scheme was estimated at about £375m.

By September 1960, the first – and only - stage of the scheme that had come into operation was Guthega power station, which had been operating as a run of river station of 60MW capacity since 1955.

Eucumbene dam, a rockfill dam with a maximum height of 381ft, was completed in 1958, and water had been accumulating in its reservoir since 1957. Tumut Pond dam, an arch structure 283ft high, was also completed in 1958, and the tunnel supplying it with water diverted from Eucumbene reservoir was completed in 1959.

The Tumut 1 power station, served by the Eucumbene reservoir and tunnel, also came into use in 1959. Tantangara dam - a concrete gravity structure - had been completed, and construction of the tunnel from Tantangara to Eucumbene reservoir was well advanced by the time The Engineer published its report.

At its peak, 10,000 people worked on the scheme that covers an area of 5,124km², mostly within the Kosciuszko National Park. In 1967 the American Society of Civil Engineers described it as one of the civil engineering wonders of the modern world, and in 2016 The Snowy Scheme was added to Australia’s National Heritage list in recognition of its role in the country’s post-war reconstruction program. According to the Australian government, Snowy ‘has become an enduring symbol of Australia’s identity as a multicultural, independent, and resourceful country.’