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As you enjoy the immense natural beauty of the mountains on the Roof of Australia tour in the Australian Alps, it is impossible not to notice and be impressed by the engineering marvel of the Snowy Mountains Hydro-electric Scheme, one of the most complex integrated water diversion and hydro-electric power schemes in the world.
December 2009
The idea behind the Scheme is simple. Water from melting snow and rain is collected and stored behind dams in lakes and reservoirs and then diverted through tunnels and pipelines down to power stations, hundreds of metres below.
Mountainous regions are ideally suited to the generation of hydro-electricity, because there is plenty of rain and snow, low temperatures with less evaporation and high mountains to provide the steep fall that is needed for the water to spin the turbines.
In its simplest form, electricity is generated by rotating a magnet inside a wire coil. In a hydro power station, this process is enhanced; the magnet is an electromagnet or "rotor" spinning inside the fixed coils or "stator" of the generator. Each generator is mounted on a vertical shaft above the turbine and water is used to drive the turbine, which operates the generator.
Transformers boost generated voltage to a level that can be economically transmitted over long distances by transmission lines to the towns and cities of eastern mainland Australia.
The amount of electricity able to be generated depends primarily on the distance the water falls (head) and the volume of water (flow) regulated through the turbine.
The type of turbine used is determined by whether the water falls from a high, medium or low head. The Scheme's power stations use Francis turbines, generally suited to medium heads. Francis turbines have guide-vanes and runners with fixed blades. These guide-vanes control the volume of water required to drive the turbine and thereby determine the amount of electrical power produced.
Once the water has passed through the turbines in the power stations, it is released into rivers to be used to irrigate farms in the dry regions west of the Great Dividing Range.
Elements of the Scheme
Snowy-Tumut Development
The Snowy-Tumut development provides for the diversion of the Eucumbene, the Upper Murrumbidgee and the Tooma Rivers to the Tumut River and for the combined waters of these four rivers to generate electricity in four power stations (Tumut 1, Tumut 2, Tumut 3 and Blowering) in their fall of 800m before release to the Tumut River and thence to the Murrumbidgee River.
The transmountain tunnel system includes the Eucumbene-Tumut tunnel connecting Lake Eucumbene with Tumut Pond reservoir. The normal function of the tunnel is to divert water through the Great Dividing Range from Lake Eucumbene to the Tumut River but, during periods of high flow in the Tumut and Tooma Rivers, water in excess of that which is required for operating the power stations along the Tumut River is diverted in a reverse direction through the tunnel to Lake Eucumbene for storage.
The total installed capacity in Tumut 1, Tumut 2, Tumut 3 and Blowering Power Stations is 2,180 MW. This section of the Scheme enables 1,380 GL of additional water to be provided over a year to the Murrumbidgee River, which has enabled irrigation production to be increased and new areas to be developed in the Murrumbidgee Valley.
Snowy-Murray Development
The Snowy-Murray development involves the diversion of the Snowy River by a transmountain tunnel system to the Geehi River, the diverted waters falling some 800m and generating up to 1,500 MW in Murray 1 and Murray 2 Power Stations. Additional power is generated in the 60 MW Guthega Power Station which makes use of the rapidly falling water of the Upper Snowy River on the east of the Divide before it reaches the main tunnel system at Island Bend.
An essential part of this development is the two-way Eucumbene-Snowy tunnel which connects the Snowy River with Lake Eucumbene. When flows in the Snowy and Geehi Rivers exceed the needs of the Murray Power Stations, water from the Snowy River at Island Bend is diverted through this tunnel for storage in Lake Eucumbene. Low flows in the Snowy and Geehi Rivers are supplemented by diverting the stored water from Lake Eucumbene back through the same tunnel and delivering it to the transmountain tunnel system leading to the Murray power stations.
Additional water is supplied to the transmountain tunnel system near Island Bend by the Jindabyne project which pumps from Lake Jindabyne the run-off from the Snowy catchment downstream of Island Bend.
The Snowy-Murray Development enables 980 GL of additional water to be provided over a year through the Hume Reservoir to the Murray River for irrigation in the Murray Valley.
Power Stations
The Snowy Mountains Scheme consists of 7 power stations – Murray 1, Murray 2, Guthega, Blowering, Tumut 1 (located 366m below ground level), Tumut 2 (located 244m below ground level) and Tumut 3.
These power stations have 31 turbines with a total generating capacity of 3,756 megawatts (MW), representing about 17% of the generating capacity of South Eastern Australia.
The Scheme's seven power stations produce, on average, 4,500 gigawatt-hours of clean renewable electricity each year to meet peak power demand.
Power from the Snowy Mountains Scheme is transmitted at 330kV to the electricity systems of NSW, Victoria, the ACT, SA and Queensland.
Dams
The Snowy Mountains Scheme consists of 16 major dams. There are five principal types of dam, which refer to the chief materials used in the construction of the dam wall:
- Rockfill
- Earthfill
- Concrete gravity
- Concrete arch
- Slab and buttress
There is one slab and buttress dam on the Snowy Mountains Hydro-electric Scheme on Outstation Creek to divert water into the Tooma-Tumut tunnel.
The most common type of dam on the Scheme is the concrete gravity type. Six of the 16 dams were constructed in this way.
The highest dam on the Scheme is Talbingo, a rockfill dam at 161 metres in height. The lowest is Khancoban, an earthfill dam at 18 metres. Eucumbene Dam has the largest reservoir capacity and Deep Creek the smallest.
Eucumbene Dam forms Lake Eucumbene, the central and largest storage area of the Scheme. It holds about nine times the amount of water contained in Sydney Harbour and covers more than 14,500 hectares. Lake Eucumbene collects water from the Eucumbene, Upper Murrumbidgee and Snowy Rivers and its enormous capacity is central to the flexibility of the Scheme to generate electricity and provide irrigation waters.
Eucumbene Dam is one of only three earthfill dams on the Scheme; the others which are much smaller are at Khancoban and Tooma. Eucumbene Dam stands 116 metres high and is 686 metres thick at its base. The outer walls of the dam are built of rock while the inner core is compacted, impervious clay.
Tunnels
The Snowy Mountains Scheme consists of 145kms of inter-connected tunnels and pipelines and 80kms of aqueducts.
Broadly the Scheme falls into two sections: the northern Snowy-Tumut Development and the southern Snowy-Murray Development. Both developments are connected by tunnels to the Scheme's main regulating storage, Lake Eucumbene on the Eucumbene River.
The longest tunnel is the Eucumbene-Snowy at 23.5 kilometres. This tunnel diverts the water of the Snowy River from Island Bend Pondage to storage in Lake Eucumbene and when required returns the water to the Snowy-Geehi Tunnel at Island Bend. It took four years to build the tunnel, a remarkable achievement when it is realised that the geology of the Snowy Mountains is predominantly granite and the diameter of the tunnel at maximum is 6.30 metres.
World tunnelling records were established on the Scheme. In 1961 the Australian firm Thiess Bros were contracted for the Geehi section of the Snowy-Geehi tunnel and in 1963 the firm established the world record for hard rock tunnelling when 165 metres of tunnel was formed in a week.
Swift progress in tunnelling was the result of many factors but two deserve special mention:
- the sliding tunnel floor and
- rockbolting.
The sliding tunnel floor comprised large, sectionalised steel working floor platform which carried rail tracks, points and crossings, drilling gantry and other tunnelling equipment. A hydraulic jacking system moved each of the three floor units forward in six stages.
Rock bolts were used to support the roof and walls of major structures such as tunnels and power stations. Steel bolts, of different length and spacing, were inserted into the rock where they were found to be an excellent anchorage for the rock.
Rock bolts were tension bolts, that when placed, compressed broken or jointed rock surrounding the tunnel and converted the rock into a self-supporting arch structure. The technique of grouting between the bolt and the rock was developed for upward sloping bolts. It is claimed that the Snowy engineers developed the world's first successful method of grouting the holes between rock and bolt.
Pumping Stations
The Snowy Mountains Scheme has one pumping station at Jindabyne and a pump storage facility at Tumut 3 Power Station.
Jindabyne Pumping Station pumps water from Lake Jindabyne through the Jindabyne-Island Bend Tunnel to the Snowy-Geehi Tunnel at Island Bend.
The pump facility at Tumut 3 Power Station returns water to Talbingo Reservoir during off-peak demands.
Bridges
Three types of bridge were built by the Snowy Mountains Hydro-electric Authority (SMA):
- reinforced concrete or steel girder
- Bailey, timber or composite
- timber span or suspension.
Most bridges in use are concrete or steel girder. Bailey bridges were originally designed as portable and usually temporary bridges. One suspension footbridge has been retained at Geehi Outlet.
The Snowy Hydro Scheme – Engineering Innovations
To be able to construct and complete a project never before undertaken in Australia required not only skill, planning and tens of thousands of workers; it also required engineers to be innovative, to find new and better ways of meeting the challenges of building the Scheme. The ingenuity displayed in building the power stations, high dams and drilling tunnels through mountains was and still is a wonder to many Australians.
The most significant of the advances in construction was the development of a technique called rockbolting, a safer and cheaper alternative to concrete lining for supporting rock in tunnel walls. An individual rockbolt was usually used to pin a piece of rock to the rock wall behind it. However, a Snowy design team found that by placing rockbolts in a pattern across the roof of the tunnel or power station so one interacted with the other, they created a structural arch.
In 1951 the Snowy Authority launched a study to find the most economical system for power transmission. The highest voltage in use in Australia at the time was 132 kV (kilo volts). The Snowy Authority decided, however, to install transmission lines of 330 kV, which has since become the standard throughout New South Wales.
Industrial safety was a vital concern of the Authority during construction. Safety practices on the Scheme were well ahead of comparable projects around the world at that time. Commissioner Sir William Hudson made the wearing of seat belts compulsory in all Snowy Mountains Authority vehicles in 1960, a decade before the rest of the country. Each employee was required to sign a statement agreeing to wear a seatbelt before they could start work. This had a direct impact on limiting serious injuries and casualties for workers through the rough and mountainous conditions.
SNOCOM was Australia's first semi-conductor (no valves) computer and one of the first dozen or so such computers in the world. Designed and built by the University of Sydney for the Authority to use for engineering and design calculations, it was delivered to the Authority’s scientific offices in August 1960. SNOCOM’s design was based around a drum memory with no disk, equivalent to 8000 bytes holding 2048 words.
The computer used paper tape for inputting and outputting information. The equipment associated with the main unit was the paper tape reader, the online punch and the printer, which was a converted typewriter that was stored in the cupboard.
Its primary function was to simulate or model the operations of the Scheme, for example, river flow analysis, survey calculations, and structural design determinations that were necessary for building power stations and dams.
Although primitive by today’s standards, SNOCOM’s use in commercial and engineering applications enabled the Scheme to be completed on time and within budget. SNOCOM was used until 1967 and the Authority was a leader in its field in the use of this technology on a project of this kind.
Tumut 3 Power Station was the first major pump-storage scheme in Australia. Pump-storage schemes use off-peak energy to pump water to a reservoir on a higher level. This water then passes through turbines to generate electricity when prices are higher.
In recognition of innovations such as these, in 1967 the American Society of Civil Engineers rated the Snowy Mountains Scheme as one of the civil engineering wonders of the modern world.
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Sources:
Snowy Hydro Ltd – www.snowyhydro.com.au
www.powerhousemuseum.com/hsc/snowy/
McHugh, Siobhan. (1989) The Snowy: People Behind the Power (William Heinemann, Port Melbourne, 1989), pp.200-201.
Collis, Brad, Snowy – The Making of Modern Australia (Melbourne, 1988; online 2009) –
www.bradcollis.net/snowy/
Australian Bureau of Statistics, “Special Article - The Snowy Mountains Hydro-Electric Scheme” (1301.0 – 1986)
Price, D.G.,
"The Snowy Mountains Scheme - the History and the Snowy Today", Australian Academy of Technological Sciences & Engineering, Symposium: The Spirit of The Snowy - 50 Years On (November 1999)
Endersbee, L.A.,
"The Snowy Vision and the Young Team - The First Decade of Engineering for the Snowy Mountains Scheme", Australian Academy of Technological Sciences & Engineering, Symposium: The Spirit of The Snowy - 50 Years On (November 1999)
Australian Department of Culture & Recreation Culture Portal –
www.cultureandrecreation.gov.au/articles/snowyscheme/
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