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Article reproduced from Year Book Australia, 1986 (ABS Catalogue No. 1301.0)
(This special article has been contributed by the Snowy Mountains Hydro-electric Authority)
In April 1966 the first diversion of water was made from the Snowy River to the Murray River, one of the many milestones in the Snowy Mountains Scheme. Twenty years later this article looks back at the development, construction and performance of the Scheme.
The Snowy Mountains Scheme is a dual purpose hydro-electric and irrigation complex located in south-eastern Australia. It impounds the south-flowing waters of the Snowy River and its tributary, the Eucumbene. at high elevations and diverts them inland to the Murray and Murrumbidgee Rivers, through two tunnel systems driven through the Snowy Mountains. The Scheme also involves the regulation and utilisation of the headwaters of the Murrumbidgee, Tumut, Tooma and Geehi Rivers.
The diverted water, together with regulated flows in the Geehi and Tumut River catchments, generates mainly peak-load electricity for the States of New South Wales and Victoria and the Australian Capital Territory, as the water passes through power stations to the irrigation areas inland from the Snowy Mountains. The Scheme reached its designed capacity in 1974 after twenty-five years of construction.
FEATURES OF THE SCHEME
(b) 2 360 GL annually of water for irrigation in the Murray and Murrumbidgee rivers.
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 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 800 m 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 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 I 380 GL of additional water to be provided over a year to the Murrumbidgee River. This water has enabled irrigation production to be increased and new areas to be developed in the Murrumbidgee Valley.
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 800 m 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 the 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.
In 1947, a Committee of State and Commonwealth officers was formed to examine the development of the water resources of the Snowy Mountains area in the broad national interest. This followed previous single purpose proposals for using some of these resources which dated back to the early 1880s.
The Commonwealth Government passed the Snowy Mountains Hydro-electric Power Act in 1949 which gave the Snowy Mountains Hydro-electric Authority the responsibility for the final investigation, design and construction of the Snowy Mountain Scheme, one of the largest single engineering works ever to be undertaken in Australia up to that time. The enterprise was established as 'a milestone towards full national development' and in serving the dual purpose of satisfying the need for increased generating capacity following World War 11 and diverting the Snowy River inland to the dry west was greeted with enthusiasm by the people of Australia.
One of the earliest tasks of the Authority was to obtain detailed survey, hydrological and geological information in steep, mountainous terrain. The analysis of this information together with advances in technology and the higher than anticipated growth in demand for electricity led to changes to the Scheme as originally proposed by the Commonwealth-States Committee. The main diversion of Snowy River water to the Murray River was made at a higher level as a consequence of the availability of dam sites and a pumping station was installed at Jindabyne for diversion of water from its lower reaches. A pumped storage project was incorporated at Tumut 3 and a number of proposed power stations were incorporated into single larger stations. In all there was a reduction in the number of power stations from 16 as originally proposed to 7 and an increase in generating capacity from 2 820 MW to 3 740 MW.
Besides the gathering of technical data, the early problems of the Authority were the establishment of stores, workshops, laboratories, offices and accommodation. Initially building materials needed to be brought from overseas in meeting priorities for post war construction. Communications needed to be developed over the area as well as road systems, camps and townships. Some 1600 km of roads were constructed and townships and main camps established at over 100 locations. Community services and amenities were also a need for the construction and associated forces which numbered over 7,300 personnel at the peak of construction in 1959.
Initially, the design of major works was undertaken by the United States Bureau of Reclamation while appropriate staff were recruited from within Australia and overseas and younger engineers were trained by the Bureau.
In the early projects of the Scheme a major change was made in the construction management of large civil engineering works. Whereas works had been traditionally constructed by day labour in Australia, the contractual system was adopted. This led to the introduction into Australia of large overseas firms which has no doubt been of great benefit to construction in Australia. Overseas contractors using Australian and New Australian labour surpassed previous world tunnelling records on many occasions. Electrical and mechanical plant was also supplied by contract to Authority specifications and at the time of construction, certain features of the Murray 1 and Tumut 3 Power Stations were of the largest attempted in the world.
Significant advances were also made in the use of rock bolts to reduce concrete lining of tunnels and underground structures.
Throughout construction a high standard of safety measures was employed and construction was renowned for the lack of industrial disputes. Undoubtedly, much of the credit for the construction of the Scheme was due to the leadership of the late Sir William Hudson K.B.E. who was Commissioner of the Authority from 1949 to 1967.
Although the Scheme was constructed at a time when the question of the effect of public works on the environment was not such a public issue as it is today this is not to say, however, that environmental aspects were not considered during design and construction. A high priority was given to soil conservation techniques and significant achievements were made in this field as well as in the protection of natural assets of the area. Under present conditions, when major environmental impact statements would be required, progress on the Scheme could have been delayed while some of the issues were resolved.
Generation commenced from the Scheme in February 1955 with the completion of the 60 MW Guthega project; and Eucumbene Dam, providing the main storage for the Scheme, was completed in May 1958.
The first transmountain diversion of water via the Eucumbene-Tumut Tunnel to the Tumut River was made in June 1959. On 1 May 1962, the Upper Tumut Works were declared in full operation marking the completion of the Tumut 1 and 2 Power Stations (600 MW), the Tooma-Tumut and Murrumbidgee-Eucumbene Diversions and the accumulation of sufficient water in Lake Eucumbene to provide regulation of water over dry periods.
Blowering Dam, which was constructed by the Authority for the State of New South Wales to regulate releases from the Scheme to the Tumut River for irrigation, came into service in May 1968 and the 80 MW Blowering Power Station began operation in August 1971. In April 1966 the first diversion of water was made from the Snowy River to the Murray River with the commissioning of the first two units at Murray 1 Power Station, and the Snowy-Murray Development was declared in full operation on 1 July 1970.
The Scheme reached its designed capacity of 3,740 MW in August 1974 when the last unit of the 1,500 MW Tumut 3 project was brought into service.
SNOWY MOUNTAINS HYDRO-ELECTRIC POWER ACT
This Act, passed in 1949, established the Snowy Mountains Hydro-electric Authority, and empowered it to provide hydro-electric works in the Snowy Mountains Area. The Authority was also empowered to supply electricity to the Commonwealth Government (i) for defence purposes, (ii) for consumption in the A.C.T. and (iii) to supply to a State, or to a State Authority, electricity not required for defence purposes or for consumption in the A.C.T.
Certain resolutions were adopted in July 1949 between Ministers of the Commonwealth and States with respect to the development and use of the water resources of the area for the generation of electricity, for the provision of water for irrigation and the sharing of water between the States. However, it was not until August 1959 when works of the Scheme were well advanced that a detailed Agreement between the States of NSW and Victoria and the Commonwealth Government was incorporated in the Act and joint legislation enacted by the States with regard to the construction and operation of the Scheme, the distribution of power and water, charges to be made for electricity and other such matters.
The Agreement also resolved differing opinions as to the constitutional powers of the Commonwealth Government with regard to the water resources of the Snowy Scheme. Under the provisions of the agreement the Commonwealth Government made a reservation of 670 GWh from the energy output of the Scheme of just over 5,000 GWh per annum, the remainder being shared between the States of New South Wales and Victoria in the ratio 2:1.
OPERATION AND MAINTENANCE
Under the terms of the 'Agreement', the Snowy Mountains Council was established. One of the main duties of the Council is to direct and control the operation and maintenance of the permanent works of the Authority for the control of water and production of electricity. The Council consists of eight members; the Chairman and Deputy Chairman representing the Commonwealth, two representatives appointed by the State of New South Wales, two representatives appointed by the State of Victoria and the Commissioner and one other member appointed by the Authority. Since the first meeting in 1959, the State representatives have been appointed from the respective Electricity and Water Commissions.
Directions by the Council are carried out by an Operations Engineer and two Assistant Operations Engineers appointed by Council. The Operations Engineer is nominated by the Authority and an Assistant Operations Engineer is nominated by each of the Electricity Commissions of New South Wales and Victoria.
Operation of the Scheme with appropriate provision for maintenance is coordinated through a series of interlocking operating plans with the objective of optimising the use of water for irrigation and electricity production within legal and physical characteristics of the Scheme. The plans are prepared by officers of the Authority and the Electricity and Water Commissions for consideration by Council.
Daily operation of the Scheme is scheduled from a Works Operation Centre in Cooma with the main State Electricity Control Centres at Richmond in Victoria and Carlingford in New South Wales. Instructions for operations are passed from the Works Operations Centre to Regional Control Centres located within the Scheme for physical implementation.
Releases from the Scheme into the Murray River come under the control of the River Murray Commission which apportions the water between New South Wales, Victoria and South Australia. Most of the water released into the Tumut River is used by New South Wales for irrigation in the Murrumbidgee Valley.
At the end of June 1985, the number of personnel employed in the Operation and Maintenance of the Scheme was 727, comprising 657 Authority personnel, 47 from the Electricity Commission of NSW and 27 from the State Electricity Commission of Victoria. Under the 'Agreement', the generating stations of the Scheme are manned by Electricity Commission personnel.
PERFORMANCE OF THE SCHEME
In the formative years of the Scheme, there were critics of its long-term economic viability in view of projected reductions in the cost of production from thermal plant as a consequence of increases in thermal efficiencies and the construction of large thermal plants adjacent to coalfields. As events have proved, the investment in the Scheme for hydro-electricity generation alone has been of great value. This arises firstly from the fact that a large proportion of the costs of hydro works are in the civil works such as dams and tunnels, etc., which have extremely long economic lives compared with thermal plants, and the fact that the operational costs are relatively low, whereas thermal plant have continuing fuel costs which are subject to the effects of changing economic conditions.
In 1984-85, the average cost of energy production by the Scheme was 2.1 cents per kilowatt hour being less than half the cost of electricity sold to bulk consumers by the Electricity Commission of New South Wales and Victoria in that year.
The connection of the Scheme since 1959 by 330 kV transmission lines to the electricity systems of New South Wales and Victoria has also been of significant economic advantage. This has enabled sharing of reserves and the interchange of electricity between New South Wales and Victoria to their mutual advantage in optimising system costs.
Extensive use has also been made of the power and pumping stations of the Scheme to provide spinning and fast reserve for both States from interrupting pumping, partially loaded units, changeover from synchronous condenser operation and the ability to start hydro units quickly with consequent savings in fuel costs of thermal plants.
When the Scheme reached its designed capacity of 3,740 MW in 1974, this figure represented 33 per cent of the capacity of the combined New South Wales, Victoria and Snowy systems, and during shortages of thermal generating plant the Scheme has been called upon to operate at the limit of the diversion capacity available.
The Scheme was designed to produce peak electricity, and good flexibility exists on a short-term basis although it is not able to replace base load generation for prolonged periods. Some increase in the diversion capacity of the Scheme may have been of advantage, but channel capacity of the rivers below the outlets of the Scheme as well as irrigation considerations limit prolonged, high discharge operation.
Because of the high degree of regulation of water available through Lake Eucumbene, a firm minimum release of water equivalent to 85 per cent of average releases is available each year. This release not only allows firm planning for electricity production but also for irrigation.
The regulation of water provided by the Scheme played an important part to mitigate the effect of very severe droughts in 1967-68 and in 1982-83 in the irrigation areas of south-eastern Australia. In 1982-83, the storage in the Scheme was reduced to 18 per cent of capacity and natural inflows to some irrigation catchments were described as being substantially below those previously recorded over some 100 years of available records.
The Scheme, however, has not been without its problems, the most significant of which was a collapse of an unlined section of the Eucumbene-Snowy Tunnel in 1970.
Major electrical and mechanical plants have performed well, but as some of this equipment has been in operation for 30 years, the time has come where replacements can be necessary. This situation also applies to communication and control systems where arrangements are in hand for replacement with high technology systems now available.
It may still be too early to assess the true significance of the construction of the Snowy Scheme particularly in regard to the inland diversion of waters. However, the Scheme has demonstrated its value in producing peak hydro-electricity, in conjunction with generating plants of predominantly thermal generators, and the objective of increasing regulated supplies of water to the Murray and Murrumbidgee Valleys.
Construction of the Scheme has also brought new skills to Australia and greatly enhanced the recreation facilities in the Snowy Mountains area. The social impact of the Scheme on the region has also no doubt been significant on the increase in size and prosperity of towns serving the area.