NAVIGATION

LAKES AND DAMS

Clive J. Price MBE, BE,
FIE Aust., Hon. FRAPI

The author has been actively engaged in the development and management of water resources for military, municipal, and recreational purposes and for hydro-electric development over the past forty years. Between 1958 and 1972 he was First Assistant Commissioner, Engineering of the National Capital Development Commission during which many of the major works, including Lake Burley Griffin, were undertaken. For the subsequent ten years he was a Director of consulting engineers, Maunsell and Partners, also working on major development projects for Canberra.

ONE of the many definitions of engineering suggests that it is the application of available resources for the benefit of man. In the construction of Canberra’s lakes and dams over the past decades, the Territory’s water resources have been developed to provide an increasing range of benefits, initially for the supply of adequate quantities of drinking water of acceptable standards (Cotter, Corin, Bendora and Googong Reservoirs), and with Lake Burley Griffin providing an ornamental setting of great beauty for the Capital and a recreational facility of inestimable value. Lake Ginninderra, adjacent to the Belconnen Town Centre, also provides a pleasant amenity and recreational facility for residents on a smaller scale as well as providing a degree of environmental protection for the Murrumbidgee River.

An assured and adequate water supply and beauty of the site were factors in the selection of the Canberra area as the site for the National Capital. Scrivener who inspected the district in 1909 was impressed by the opportunity it afforded for ‘storing water for ornamental purposes at reasonable cost’. In making his choice, Scrivener unknowingly selected the spot where, in pleistocene time, a freshwater lake had existed, created when scree from Black Mountain blocked the channel of the Molonglo River, damming the water back to a height of about 556 m above sea level. In his 1909 contour survey, Scrivener showed four alternative weir sites for the construction of an ornamental lake with a water level of 556 m. These were the first schemes for a lake at Canberra and the concepts were similar in size and shape to the lake as it exists today.

In determining that the future Capital would have adequate water supplies, Scrivener proposed that the Capital Territory should include the catchments of the Molonglo and Queanbeyan Rivers to prevent pollution of the rivers before they flowed through the city site. Legislation to create the Territory was passed by the State and Commonwealth Governments, but the Molonglo and Queanbeyan River catchments were excluded.

However, the Seat of Government Act which led to the establishment of the Capital Territory on 1 January 1911 gave the Commonwealth paramount rights over the Molonglo and Queanbeyan Rivers and their tributaries, and made the State of NSW responsible for protection of the river waters from pollution. The new Territory also included the catchment of the Cotter River and it was to be on this river that three of Canberra’s four water supply storages, Cotter, Corin and Bendora were to be constructed.

The wisdom of the ‘ Founding Fathers’ has enabled a substantial heritage to build up through the lakes and dams which have emerged as the rivers and streams have been developed for water supply, for active and passive recreation, for water quality control, for town centre cooling and as an integral part of the complex planning of a National Capital. The significance of Lake Burley Griffin and its parklands as the centre-piece of Canberra can now be seen and this, more than any other single feature, has led to the acceptance by the people of Australia of Canberra as their National Capital.

Lake Burley Griffin
Fig. 4.1: A general view of Lake Burley Griffin with the Australian National University and the Royal Canberra Hospital in the foreground, and the Parliamentary Triangle and Russell Defence Offices in the middle distance. Chapter Four

Lake Burley Griffin

Lake Burley Griffin is about 9 kilometres long, covers a surface area of 678 ha and varies in width from 300 to 1200 metres. It has about 33 kilometres of landscaped foreshores which provide access to 314 ha of parkland and 142 ha of the Eastlake Wetlands, a breeding ground for many species of water birds. It is a shallow lake with a maximum depth of almost 18 metres near Scrivener Dam and a mean depth of nearly 4 metres.

The lake evolved out of the investigations and debates of earlier years combined with the opportunities to adapt rapid advances in technology in a favourable political climate. The National Capital Development Commission, under the leadership of Commissioner John Overall, recognising the well of political and public support for the development of Canberra in the late 1950s, tackled forcefully the problems remaining from earlier years. The application of new and sophisticated techniques for dam and gate design for flood control, and of intensive hydrological activities led to construction of a dam across the Molonglo River below Black Mountain in 1963 and the filling of the Lake in 1964.

Completion of the physical works is not the end of the story because the maturing of the surrounding landscape in which 55,000 trees were planted and the introduction of beaches, picnic areas and other facilities around the lake shore is a continuing process which will delight the generations to come. The lake and its landscape lie at the heart of the National Capital but are also part of an open space system which provides a variety of recreational experiences for residents and visitors to Canberra.

The story of the lake’s construction is one of vision and short-sightedness, of confidence and doubts, and of procrastination and performance out of which emerged a water feature consistent with the vision of Scrivener and the intentions of Walter Burley Griffin.

When the conditions for the competition for the design of the Capital were announced in 1911, they were accompanied by a more detailed survey on which Scrivener had shown the level reached by a flood in 1891. This and other information prompted most competitors to include a water feature in their designs.

An engineer, J.A. Smith, was one of the majority of judges who awarded first prize to Walter Burley Griffin in 1912 for his entry in the Federal Capital Design Competition. Their decision was subsequently upheld by Mr King O’Malley, the Minister for Home Affairs. Griffin had placed the central basin of his lake scheme across the land axis of his design, with two formal basins at each end forming his ‘water axis’. Around these three basins and on these two axes, his main civic design compositions were arranged. Not content with this limited area, he submitted another plan ‘rendered on cambric in monotone’, to indicate the dominant topographical features and their relationship to the proposed architectural and landscape development.

This shows the irregular ‘West Lake’ at the same level as the formal basins, 556m and the balancing ‘East Lake’ set six metres higher. This was certainly the grandest scheme submitted, yet it had an appealing simplicity and clarity.

Griffin was a man with remarkable powers of imagination and a genius of topography. Unable to visit Australia, he studied a plaster model of the city site to a scale of about 1:5000, provided for the information of competitors in the British Consulate General in Chicago. From this, he had grasped, as his rivals and critics had not, the significance of the Molonglo flood plain.

The basic fact was that right across the middle of the city site lay a belt of land, averaging 0.8 km in width, which, despite the Competition conditions’ promise of a regulating weir at least 23 km above the City, would always be in danger of flooding. It could not, except with great difficulty and expense, be built upon.

Two alternatives were possible, either the flood plain could be treated as a continuous park bordering a shallow stream, designed to suffer periodical submersion without damage, or it could be permanently flooded by damming the river at a point below the City, thus forming a chain of natural lakes.

As to which of these alternatives would be more effective in uniting the two halves of the city in a scenically dramatic way, Griffin was in no doubt.

He wrote in his competition report:

“The main waterway, the Molonglo, is left in its present state in the lowest and widest regions” ie., below the City . . . “. . . Next above and at the second of the weir sites suggested in the invitation program (i.e. at Yarralumla) a dam of very modest proportions, constructed in connection with one of the roadway crossings, floods the lower outlying informal lake (i.e., the West Lake) and the triple internal architectural basins which bound on three sides the government group for the reflection of its buildings, and for improvement of humidity conditions in the heart of the City . . . The most difficult problem connected with the waterway through the centre of the site is to minimise its interference with traffic and at the same time least cut up areas.” “The circular pools (ie., the East and West Basins) and the connecting (Central) basin provide three water bodies, each complete in itself, located in the spaces between the direct lines of communications from centre to centre. At the same time, because of their largeness of scale and severe simplicity, they conform to the architectural character of the centre of the City with its monumental groups and throngs of busy people.”

Although awarded first prize by the Minister, Griffin’s design was referred, along with other premiated designs, to a Departmental Board of experts for advice. The Board, on which Scrivener served, produced a scheme of its own, which contained another lake scheme, a near relation of the entry submitted in the design competition by the Australian group of Scott, Griffiths, Coulter and Caswell.

When construction of the capital was inaugurated on 20 February 1913, the Board’s scheme was the basis for the City’s development. Griffin subsequently was appointed ‘Federal Capital Director of Design and Construction’ on 18 October 1913. He then published his Preliminary Plan which shows the modifications resulting from his examinations of the site and his discussions with the Board.

He further refined his plan producing a “Schematic” Plan two years later. This was examined by the Parliamentary Works Committee in their enquiry into the Provision of Dams for Ornamental Waters in 1916. This forced Griffin to defend his scheme against the criticism of the former members of the Departmental Board and others. Scrivener, for instance, said “We would not agree with Mr Griffin. One of the points of contention being the form of the lake. I regard the artificial form as much less beautiful than the natural contour. It gets rid of the bays and indentations that are the principal charms of Sydney Harbour”.

A Griffin plan
Fig. 4.2: A Griffin plan with East Lake added to show its relation to the present Dairy Flat Road, Pialligo Avenue and the Airport. This widespread East Lake was to be 6 metres higher than the present Lake Burley Griffin.

Griffin was unshaken in his belief in the formal elements of his scheme, defending it vigorously from all attack. He worked out schemes for the treatment of the formal boulevards that were to surround them, which he claimed were ‘one of the reasons d’etre of the ornamental waters’.

In spite of Griffin’s impressive stand, the Committee decided that the formation of East Lake should be indefinitely postponed, and that the shape of the formal basins should be modified, decisions which have persisted to the present day.

Most of the construction work that had occurred up to 1916 had been outside the City Area and therefore beyond Griffin’s theoretical control, such as the dam on the Cotter River for the city’s water supply which was completed in 1915.

Although Griffin’s revised plan of 1918, with a few amendments, became the official plan for the National Capital following the passage of the Seat of Government (Administration) Act in 1924, there was a number of significant alternative, though interim, lake proposals considered over the years. In the main they consisted of schemes which would allow the progressive development of the full proposal and consisted of a number of weirs established to provide “a ribbon of water” between Yarralumla and the Causeway. The more significant of these were referred to Parliamentary Standing Committees on Public Works whose reports provide enlightening reading and an insight into the difficulties of those earlier years in assessing the feasibility of measures for flood and drought provisions.

The Owen and Peake Report prepared in 1929 is representative of the thinking of this intermediate period and its conclusions drew attention to several hydrological issues which greatly influenced the decisions on the size and security of storages. These issues were examined in more recent studies and with the support of more extensive data and research were able to be resolved. Thus the original concept proved practicable. A third ribbon of water scheme was suggested to replace the West Lake which had been incorporated in the Canberra Plan in 1933. The Wilson Report of 1955 brought the full proposals back into line and with the subsequent appraisals of 1958-1964 led to the present lake.

These earlier schemes were summarised in a memorandum of April 1956 to the Parliamentary Standing Committee on Public Works (Metric equivalents have been substituted):

The Owen and Peake Report of 1929, discussed the first Ribbon of Water Scheme suggested in 1926, but not approved by the Public Works Committee. That entailed a weir at Yarralumla at 548m level, and was to bank up the water only as far back as Commonwealth Bridge.

The Owen and Peake Report suggested that, until the lake scheme was implemented, some of the objections to the 1926 Ribbon Scheme could be met by adding to the Yarralumla weir another small weir, at 551 level, near Scott’s Crossing, to back up the water to the weir already constructed to the 553 level at the power house. This in turn backs up the water to the Causeway — the beginning of the former East Lake. This second ribbon scheme would therefore have made use of the main Yarralumla dam, the Scott’s Crossing weir, and the power house weir to provide a continuous ribbon of water through the city. This scheme was not approved. It would have been relatively inexpensive, but depended entirely on the assumption that large control dams could be built on the Upper Queanbeyan River to provide water for city parks, etc., and sewerage dilution, as well as for flood control.

Otherwise there would have been risk to the Commonwealth Bridge in flood times, through backing up by the Yarralumla weir.

The third ribbon of water scheme, substituted for the west lake on the Canberra Plan of 1953, was a different proposal altogether. It aimed at placing a low weir at Yarralumla, and also a large dam at Lennox Crossing to form three main lake basins, and to use the area surrounding the ribbon for special gardens and recreation areas. This scheme would be enormously expensive — much greater than the lakes scheme — and, making no provision for flood control, would have been subject to frequent floodings. It was subsequently shown that the foundations for that weir at Lennox Crossing were most doubtful in that position, and a dam on the upper reaches of the Queanbeyan River for flood control would be impractical. A tremendous amount of water would be needed, covering a vast area of good country, and even then it would only delay the peak of the floods for a few hours.

It was stressed in the Owen and Peake Report that because of lack of data their conclusions were not definite.

The Wilson Report was made after a very careful survey of the area and all the records, which are now a deal more complete than in the time of the Owen and Peake Report. Mr Wilson based his findings on a somewhat different basis to the former report, but has left no ambiguity about the aims of it and the probable results. He makes it plain that, in drought years the lakes could fall by as much as O.84m, but the occasions will be very few and in 50 per cent of the years there will be no fall at all. It is shown that the lakes scheme can be successfully implemented with those limitations, but a dam on the Upper Queanbeyan would be essential if some of the other requisites, such as flood control efforts, were to be insisted upon.

The Wilson Report made no attempt to provide water for Sewerage dilution, as the amount required is now so great that the present river flow would not cope with it, and other measures will be required. He concluded with the suggestions that the lakes scheme should be implemented at the 556 level, and the disadvantages of it accepted for the time being. In the unlikely event of them proving really objectionable, it will still be possible to construct the smaller of the dams suggested on the Queanbeyan River to supplement the flow occasionally.

The point to be remembered is that really, effective flood control would be impossible and the ribbon scheme from that aspect alone is most undesirable, but it is essential to carry on immediately with planning and preparatory works on the lakes, gardens, and bridges, and this matter must be determined without delay.

The question of the aesthetics of retaining west lake in the scheme was doubted by the chairman of the Planning Committee, but a large majority of the witnesses in the Senate Committee’s Inquiry were in favour of it.

Mr Wilson’s conclusion that the lakes scheme should be implemented at present without the dam on the Queanbeyan River for drought and flood control, was made with the full knowledge of the Owen and Peake Report. That report showed that even with the big dam at Googong, the 1925 flood would have been controlled for only 12 1/2 hours.

Sailing on Lake Burley Griffin
Fig. 4.3: Sailing on Lake Burley Griffin. Photo — NCDC.

The Senate Inquiry of 1955 led to the establishment in 1957 of the National Capital Development Commission which quickly recognised the importance of the lake. It was able to draw on the earlier studies and on the technical resources and hydrological data available through Commonwealth departments and authorities. NCDC studies led to a greater assurance on such issues as the behaviour of the lake in terms of floods and droughts and of scour and siltation. Other studies arranged by NCDC were able to provide satisfactory answers on water quality, effects of climate and health, hazards of unsightly margins, of mosquitos and midges and the possible disbenefits from changes in land uses.

Swimming in the lake
Fig. 4.4: Swimming in the lake is permitted everywhere except in the Central Basin. This is the beach at Black Mt. Peninsula. Photo — Pieter Arriens for NCDC.

A number of technical papers listed at the end of this chapter provide further detail on the investigations and designs for the Scrivener Dam and Lake Burley Griffin. It is useful however to record a few interesting points relating to those issues which had plagued the earlier investigations.

Of all the investigations carried out, the hydrological studies were by far the most significant. The best use had to be made of the limited information available on weather and river flows. The question of the availability of water with or without an upstream storage and the effect of future flows, particularly in the Parliamentary Triangle, could not remain unresolved.

The Molonglo River which feeds the ornamental lake in Canberra with an average annual inflow of 180 cumecs has three main tributaries which rise to the east, south-east and south of the City. The catchment with an area of 1810 km2 is subject to the spillover from heavy coastal storms which have, in recent years, produced flood peaks up to 3,540 cumecs (cubic metres per second).

Following the detailed theoretical analysis of rainfall patterns and river flows,4 a river model was constructed which was used to test the adequacy of the theoretical findings. It was shown that these theoretical calculations were extremely accurate and the verification obtained from the model studies was most reassuring and enabled far more detailed information to be provided on many aspects. The usefulness of the main model studies led in later stages of the design to the development of more specific model studies, and, in all, some four models were constructed. The main river model also served as a useful medium for informing those in authority and the public at large of the implications of the lake scheme.

Some of the detailed investigations carried out on the models related to the alignments of the lake shore, the positioning of the bridges, the details of flood levels and the behaviour of the flood gates. For example, Kings Avenue Bridge was resited about 50 metres north of its original proposed location increasing the useful waterway from 60 to 80 per cent of available area. The studies also confirmed that with the proposed gates the lake level of 556 m could be maintained in the central areas for all floods up to 2,300 cumecs and that at the design discharge of 5,600 cumecs the level of the lakes in the central area would not exceed 560 m and that such levels would be controlled not by the lake structure, but by the bar of Black Mountain Peninsula.

The use of the models also allowed studies to be made of the shore alignment, the design of the energy dissipator, the handling of floods through the East Lake area and the potential benefits to be achieved by realigning the main channel leading to the creation of interesting islands.

At the other end of the hydrological scale careful studies were made of drought conditions over past years and allowances made for evaporation, irrigation and leakage. It was determined that the lake would function quite satisfactorily within a metre of the 556 m water level without an upstream storage. By this time the application of British Standards for dilution of sewerage effluent was no longer relevant or practicable.

In addition to general ecological studies, specific investigations related to fogs, fish, the behaviour of aquatic plants, the likely extent and magnitude of waves, conditions required to prevent breeding of mosquitoes and other insects, and matters relating to the use of the lake for a wide range of recreation activities. These were carried out to confirm the feasibility and establish the basic criteria for the design of the lake itself.

The investigations extended in this way over the matters of geology, the expected rise in the water table, the quality of the water, the effect of upstream operations, including discharge of effluents into the Molonglo River and matters of turbidity, sedimentation and erosion.

This latter field of study probably gave the greatest concern because the lake was to be a relatively small, shallow body of water downstream of a large catchment subject to very high flood discharges, capable of carrying considerable quantities of sediments. Hydrological science at the time did not offer a reasonable method of estimating the proportion of such sediments that would be trapped by the lake.

After extensive studies using a number of highly respected advisers, it was determined that provided satisfactory precautions were taken in the catchment, the lake could be expected to function reasonably satisfactorily. Nevertheless, some floods could deposit substantial quantities of sediments, particularly in the upper reaches of the lake. It was impracticable to carry out quantitative studies of sedimentation in the lake and the design has therefore endeavoured to make conditions as favourable as possible for minimum sedimentation.

Under small floods with only one gate down at the dam, an opening 32 metres wide by 5.2 metres high can allow large quantities of sediments to pass straight through the lake. Under any floods above 2,300 cumecs five such gates would be down.

Bed load traps were provided upstream of the dam and widespread soil conservation measures were carried out throughout the ACT portion of the catchment. In addition, an agreement was made with the State Government for a large soil conservation programme to be undertaken in the much greater NSW portion of the catchment. Much of this programme was well underway by the time the lake was built. Such programmes of course make major improvements to property values and hence landholders paid one third of the costs with the Federal and State Governments sharing the remainder.

Scrivener dam consists of a concrete gravity section with five 32 metre x five metre flap gates between two concrete gravity buttress non-overflow sections of 71 metre total length, and of earth embankments 184 metres long of which a total length of 40 metres has a centre concrete cut-off wall founded on rock and one metre thick. Maximum structural height of the dam is 36 metres.

Minister for the Interior
Fig. 4.5: Minister for the Interior, J.D. Anthony, invites the Prime Minister Robert Menzies, to inaugurate Lake Burley Griffin in 1964. Photo — NCDC.

The dam is founded on quartz porphory which was covered by alluvium of varying thickness. On exposure of the foundation under the river itself, a combination of geological faulting required the use of post-tensioned cables to tie several blocks of the dam back to the sound rock upstream.

A roadway is provided across the dam to serve as a river crossing between Woden and the City and Belconnen. It is also used as a means of gaining access for the maintenance of the gates.

The size of the design flood, that is the flood which had to be handled by the structures in the flood plain was determined at 5,600 cumecs. The structures were also examined for a flood of 8,500 cumecs in terms of any possible catastrophic damage arising from this ‘max max’ flood situation.

In calling tenders for the design, manufacture and erection of the five 32-metre crest gates to pass such floods, it was necessary to ensure the minimum obstruction to the passage of debris. The neatness and appearance of the gates also was considered of great importance. The gates as erected are fish belly flap gates designed by Rheinstahl Union Bruckenbau, West Germany. The water load is carried by the steel skin plate of the fish belly section to six cross beams. Each of these cross beams is supported by a hinge, anchored to the concrete dam crest and the four centre beams are also supported approximately at their half points by hydraulic jacks.

The main criteria in the control of Lake Burley Griffin is to keep the water level in the Parliamentary Triangle as near to 556m as is possible with the gates provided in the dam. Three one metre X one metre sluice gates have been installed and can automatically adjust the outflow from the lake for a range of 150mm change in water level.

By setting the float-operated control equipment for the first sluice gate at slightly below the desired Top Water Level, the mean annual inflow of 5.1 cumecs will raise the water level to RL556. Under steady flow conditions the sluice gates can pass a discharge of approximately 60 cumecs without allowing the water to rise above 556. During periods of minor floods the filling of the lake storage above 556m is expected to enable the sluice gates to handle floods with peak discharges of less than 100 cumecs. In some years it will not be necessary to use the flap-gates for flood discharge at all. The longest recorded period that flap-gate operation would not have been required was from December 1925 to March 1929.

The first contract (for the gates) was let in May 1960, work commenced on the Dam in September 1960 and the storage commenced to fill in September 1963. Apart from the unfortunate combination of faulting encountered in the foundations and from normal troubles experienced in the installation of such large gates, the construction of the Dam proceeded well.

The treatment of the lake margins5 varies according to their location and has regard to function, hydraulics, cost, maintenance and the landscape value of particular designs. The interest and beauty of the lake arises as much from the variety in the 33km of shoreline and its treatment as from the area of water itself. Apart from the formal south bank of the central basin, the shoreline is quite informal and seeks to provide this interest. There are four main types of margins.

  • A concrete wall consisting essentially of a low reinforced concrete retaining wall capped by a coping is provided in the formal sections of the lake, particularly where hydraulic conditions require such treatment and the foundations lend themselves to this type of wall. It is designed to allow a fall in lake level without an exposure of the lake bed. The precast coping is capable of adjustment and has enabled a most satisfactory line to be achieved on the long straight margin.
  • In other areas a grouted rock wall has been provided and is an effective treatment from the point of view of maintenance and freedom from erosion and has been extensively used in the upper reaches of the lake where the burden of the incoming floods have to be withstood.
  • The third form of edge treatment was the provision of sand and gravel beaches which are designed to allow some protection to the subsoil and as a provision for entry to the lake for recreational purposes.
  • The fourth type of margin is essentially a natural margin where there are rock outcrops and steeply sloping stable shores. The western areas, in particular, have extensive sections of such foreshores which have been planted for landscape and stability purposes.
Scrivener Dam
Fig. 4.6: Scrivener Dam which creates Lake Burley Griffin, discharging flood of 1976. Photo-NCDC.

The location of the lake margins generally follows the 556m contour which proved an extremely economical location. There were several areas of shallow depth or special functional requirements which have been developed to provide particular features in the lake. For example, in the West Lake area near the University, cut and filling resulted in a larger lake and an interesting island. Similarly, a balanced programme of earthworks led to the developments of the boat harbour in East Basin, the Nerang Pool in an area which was formerly swamp land and the formation of Yarralumla Bay and Lotus Bay for boat shelter. To allow a larger triangular sailing course for races, the ‘finger’ of land at Yarralumla Bay was cut out but the ‘finger nail’ left was another island (Spinnaker). The lake has six islands altogether.

Any reference to Lake Burley Griffin would not be complete without a statement on the design and construction of the traffic bridges which contribute so much to the total composition of the central areas. These are discussed in Chapter One.

Thus it was with the completion of engineering works in September 1963 that all that was required was a supply of water — something beyond the powers of Prime Minister Menzies, Commissioner Overall or the many highly skilled and enthusiastic professionals who had contributed so much to the lake’s construction. As the dry season which had so favoured construction operations continued, doubts began to emerge that the National Rowing Championships, scheduled with an abundance of faith for Lake Burley Griffin 2 May 1964, would become a modified version of the Todd River Regatta. An alternative course was being prepared for use on a partly filled lake when at the end of April 1964 heavy rains fell on the catchments, the lake filled and the Regatta was held successfully, though in the midst of some flotsum and jetsam from the receding flood.

In the years since then, the lake and its parklands have proved universally popular. Power boats are not permitted, other than for safety patrols and the coaching of rowing crews. However on most Saturdays and Sundays in summer, more than 10,000 people are attracted to the lakeshore, more than one-third arriving by car at the one time. The increasing usage of the lake and its foreshores is generating a demand for more beaches and the provision of further facilities associated with direct use of the lake, such as boat sheds, clubhouses, boat launching areas, parking and other structures and amenities.

The pressure of people in some areas leads to conflicts between different kinds of uses and users that need to be resolved by management. There is also increasing demand for sites for tourist oriented development. As the lake and the foreshore are a finite resource, it is desirable that planned uses and facilities are located in accord with its physical character and environmental capability and that the management implications of this are recognised.

Swimming in the lake is only prohibited in the formal Parliamentary area but water quality problems have occasionally caused closure of the lake for short periods. Despite the difficulties in controlling the quality of all inflows, the lake water quality remains mostly acceptable by swimming water quality criteria.

Continuing careful attention to all aspects of lake management is vital, particularly as the lake matures.

Lake Ginninderra

It is not surprising that following the impact of Lake Burley Griffin on the Canberra scene, the availability of water and its maximum beneficial use became an important factor in the development of Canberra’s new towns. There was in the mid 1960s a sensitivity to environmental matters, an awareness of the need to preserve water quality and a changing lifestyle which placed greater emphasis on social and recreational matters.

Lake Ginninderra is about one-sixth the size of Lake Burley Griffin
Fig. 4.7: Lake Ginninderra is about one-sixth the size of Lake Burley Griffin. Belconnen Town Centre
is being developed on its southern foreshores. Photo — NCDC.

In the early planning considerations for the new town of Belconnen, the pattern of neighbourhoods and regions focusing on the town centre defined the general location for that centre. In the detailed consideration of the town it was realised that an opportunity existed, subject to detail study, for the introduction of a water feature into the design of the town centre. The concept of a ‘town in a park’ and even ‘the lake in the town’ were not unreal and the successful completion of Reston in USA though on a smaller scale encouraged thinking along these lines.

Although the concept was valid, the basic hydrological data for Ginninderra Creek was lacking and an analysis of comparable catchments was necessary to define a realistic lake area and to assess the need and extent of any make-up storage.

By 1967 the Belconnen urban areas were developing rapidly and already a trunk sewer had been constructed on an alignment which, under some lake proposals, would be flooded. Planning of major arterials also would be influenced by the arrangements of a future lake.

Ginninderra Creek itself rises in the Hall area of the ACT. It flows for several kilometres in a generally south-westerly direction crossing the Barton Highway about 6.5km on the Canberra side of Hall. At a point close to the Belconnen Town Centre, the creek turned sharply in a northerly direction for about 3 km, then turned again in a direction generally slightly north of west to flow eventually into the Murrumbidgee River.

Feasibility reports prepared in 19676 examined the following aspects:

  1. The feasibility, scale, treatment and cost of a water feature adjacent to the then proposed Belconnen Town Centre.
  2. The establishment of water levels and flood heights based on the hydrology and land form surrounding the Creek as a background for development proposals.
  3. Consideration of the ability of Ginninderra Creek to maintain the lake level and possible sources of toppingup water if required. Consideration of sedimentation problems and the appearance of water; and
  4. A study of the capacity of the existing trunk sewer to safely withstand the loading resulting from lake development above.

The initial considerations related to catchment yield and make-up requirements. The assessments were made on the basis of the Jerrabomberra catchments adjusted for the different rainfall records as provided by Mt Campbell in the Jerrabomberra catchment which has similar land characteristics and uses although its soil characteristics are not comparable. Ginninderra is generally composed of relatively impervious clay and silty clays while the Jerrabomberra catchment has soils which are relatively permeable.

It was demonstrated that the natural flow of the Creek would not maintain a full storage at all times with the lake level at RL578. The maximum draw-down without topping up with water from an external source was estimated to be of the order of 0.64m. Such topping up water could be provided in the early stages of development by either the use of treated waste water, town supply or ultimately by water from a dual purpose upstream storage.

In the later years, run off from the catchment in the Gungahlin area was expected to increase appreciably with the progressive urbanisation of Gungahlin, thus minimising or eliminating the need for topping up the lake. Since its establishment, however urbanisation of Gungahlin has not proceeded but those parts of Belconnen in the lake catchment have mostly been urbanised and the lake has not yet needed topping up.

The full supply level of 578 was adopted after an analysis of the shoreline slopes around the perimeter for levels of 576 and 578. The shore slope characteristics at both levels are similar, the higher perimeter provided some 10.5 km of shoreline compared with 8.4 km at the lower level. The higher dam was selected as it provides better facilities for recreation, such as rowing and sailing.

The earth and rock fill dam has therefore been constructed with a top water level of 578 and an adjacent culvert spillway. The dam served not only to form Lake Ginninderra but provides the arterial road linkage between Belconnen Town Centre and North Belconnen.

The examination of the trunk sewer demonstrated that with adjustments to vents and manholes its structural capacity was adequate. However, the use of this pipe as a main sewer has been progressively reduced with the further development of the Town Centre and the main sewer network.

A section of the main however has continued to be used for the dispersal of the warm water discharge from the integrated air-conditioning system for the Town Centre. About two km length of this main has been adapted to this purpose by the introduction of some 24 dispersing outlets. The hot water is fully dispersed within some 6m of these outlets.

The net cost of constructing Lake Ginninderra was quite low due to such factors as the need anyhow to carry a major arterial across the creek on some major structure, and the augmented land values around the lake.

Lake Ginninderra is a delightful waterscape which is being enhanced as landscape materialises and development proceeds. Earlier visions of having areas in which housing penetrates virtually to the foreshores as occurs on this scale of water-way elsewhere have been thwarted by the presently popular desire to preserve all such areas for public availability. The partially completed Town Centre has not yet established the quayside effect of the mature development but the prospect remains and the opportunity exists in years to come to build on this heritage provided in the 1970s.

Canberra’s water supply storages

The storages for Canberra’s water supply were initially supplied on the Cotter River. In 1912, construction of the first dam commenced and when completed in 1915 the 20m high concrete Cotter Dam had a capacity of 1850 megalitres. The water was pumped from the dam to a storage reservoir on Mount Stromlo, where it gravitated to the city service reservoirs. A pumping scheme was considered to be more economical than a gravitation one since the loss of interest over many years on the additional construction cost of the gravitation scheme would have proved much greater than the cost of pumping.

The water supply system in the first stage was for a population of 25,000 which proved more than adequate for more than 30 years. In 1945, the population of Canberra was only 13,000. In 1950-51, the dam wall was raised a further 7.3m to increase the reservoir’s capacity to 4,700 megalitres.

In 1958 to meet the needs of Canberra’s growing population work began on the 47.2m high Bendora Dam, the first thin wall, double curvature-type dam built in Australia.7

This storage on the Cotter River was recommended by the Parliamentary Standing Committee on Public Works after considering two sites, the one on the Cotter and the other at Googong which was favoured technically. Because the Committee doubted that effective control could be exercised over the Googong catchment area and because it considered that the resumption of the whole Queanbeyan River catchment area for control purposes would remove the capital cost advantage of the Googong site, the Committee, on balance, recommended the Upper Cotter site, stipulating that water should at first be pumped from the storage but later a gravitation system be constructed.

Walter Burley Griffin
Fig. 4.8 Walter Burley Griffin’s prize-winning plan for Canberra in 1912.

When construction of the Bendora Dam commenced in 1958, Canberra had begun a population explosion and it was obvious that another dam would be needed soon. Investigations for a new dam began in 1961 while the Bendora Dam was being constructed. By 1963 it had been decided that the third dam, the Corin, should be built on the Cotter River as soon as possible. The investigations indicated that the subsequent site should be at Googong but drew attention to the Upper Murrumbidgee as a future potential source. For example a tunnel could be built from the upper Murrumbidgee near Tantangara to lead water into the Cotter Valley upstream of Corin.

Corin Dam acts as a reserve storage to release water down river to Bendora Dam for supply to the Canberra Water Supply system via the gravity main.

In drought periods and in the years when the water supply demand is approaching the safe yield from the installations on the Cotter River it will be necessary to operate all of the storages in order to obtain the maximum yield. This will require Bendora Dam and the Lower Cotter Dam to be drawn down in the latter part of the summer and autumn to provide storage availability for rain falling anywhere on the catchment. If in these critical years the two lower dams were operated full for optimum pumping and gravity conditions, any rain falling below Corin Dam would be lost over the spiliways of the lower dams.

The design and construction of Corin Dam is well documented in the report on this subject prepared by the Commonwealth Department of Works.8 The following general description of the project is provided for completeness of the record.

Alternative dam proposals included:—

  1. rock fill dam with central earth core;
  2. concrete multiple arch dam; and
  3. earth fill dam.

The earth and rock fill dam was selected as the most satisfactory alternative. The complexity of the concrete multiple-arch dam combined with the uncertainty of the foundations for this type of structure made this alternative less acceptable having regard to the assured foundation for the earth and rock fill alternative. This resulted in a 76.2m high earth-and-rock-fill structure incorporating a side channel spillway and an outlet tower leading to the diversion tunnel. The valves at various heights in the tower allow draw-off at various reservoir levels.

Particular care was taken during construction to minimise the pollution of the live storages in the lower catchment. This applied particularly to the placement of rock fill. Information, particularly on the performance of German rock-fill dams, indicated that the initial movement of this type of dam was considerably reduced by rolling the rock-fill in layers, as contrasted with those constructed by dumping methods. It was reported by the Snowy Mountains Hydro-Electric Authority that the contractors were favourable toward the technique of rolling rock-fill. It was realised that sluicing the rock-fill during the placing process would pollute the river, and this was confirmed by observation of the construction of the Geehi Dam. Continued pollution of the Cotter River during the dam construction would have been most undesirable because it was the sole source of Canberra’s water supply. It was decided to roll the rock-fill in layers without sluicing after the dry and wet strength of the rock was tested and the quartzite rocks showed only a slight decrease in wet strength compared to its dry strength.

A side-channel inlet to the spillway chute was chosen to minimise rock excavation and to ensure reasonable approach conditions to the spillway crest because of the oblique flow from the storage toward the spillway crest.

The decision to develop the terminal structure of the spillway as a ski-jump instead of a stilling basin was a matter of economics. The disadvantage of the ski-jump is the pollution of water whilst the scourhole is being formed. A basic problem of shaping the ski-jump with a spillway with an uncontrolled crest is to cause the small discharge to shoot, leaving the resulting scour remote from the ski-jump structure. This was achieved by superelevating and stepping the ski-jump, thus concentrating low flows to the lower step of the ski-jump where it shoots in a low angle trajectory.

The Cotter catchment is restricted to its use as a water supply catchment in the absence of full water treatment. However, at Corin recognition has been given to the opportunity it provides for the enjoyment of the attractive scenery and of the bushland comprising the catchment. Good road access has therefore been provided to the site across the Dam crest and over the spillway via a bridge to a turning circle and parking area on the left bank. This has provided a popular terminal point for tourists visiting the Brindabella Reserve and the Gibraltar Creek falls.

The construction of the Corin Dam was commenced in March 1966 and completed in October 1968. Together with the other Cotter River storages, it will supply a total Canberra-Queanbeyan population of about 225,000 people. Investigations of possible storage sites for the next dam began in September 1967 and encompassed a wide range of possibilities in the region. This report concluded that the next dam should be built at Googong.

Googong Dam

Googong Dam had been contemplated from the time of the initial nomination of Canberra as the site of the Nation’s Capital and its investigation has been directed from time to time with a view to its use for water supply, flood control, lake provisions and for recreation.

The instruction for the guidance of surveyor C.R. Scrivener in selecting the site for the National Capital in 1908 gave as a primary requirement “That it include the catchment area of the water supply for the Capital — such water supply to be of sufficient magnitude to place the question of volume at all seasons and purity beyond doubt”.

Scrivener nominated 2,628 km2 in the catchments of the Cotter, Queanbeyan and Molonglo Rivers and a request was made to the NSW Government for the surrender of the land. But after negotiations only the Cotter catchment area was included and in respect of the Queanbeyan and Molonglo Rivers, the Seat of Government Acceptance Act, 1908 Schedule 1, provides safeguards.

Thus although not a dam in the ACT Googong has become an integral part of Canberra as a major source of water supply and progressively as a major recreation source.

That Googong provided an assured site for a dam is conveyed by the following extract from an attachment to the Owen and Peake Report of 1929. (Metric equivalents have been substituted):

Griffin
Fig. 4.9: Griffin’s preliminary plan for Canberra showing the three formal Basins of his ‘water axis’and the irregular West
Lake and portion of the East Lake.

The site of the proposed Googong Dam is by River 27 km above the Commonwealth Avenue Bridge and 10km above the Town of Queanbeyan. It lies between two steep hills and at the low end of extensive river flats which will provide a good storage ground. The river bed level is RL612 or 54m above the deck of Commonwealth Avenue Bridge. The catchment area above the site is 875 km2

Dr Woolnough has inspected and reported upon the site and extracts from his report are as follows:

Summarily it may be stated that the site is as nearly ideal from a geological point of view as it is possible to imagine. The area is occupied by a thick series of Silurian sediments and volcanic rocks which are intruded by a considerable mass of granite of somewhat more recent date. The sediments are dominantly slatey in character and no noteworthy outcrops of were seen in the section examined. The slates being easily eroded, have caused the formation of a wide open valley in the neighbourhood of the head station. It is this open valley which will supply the storage for the proposed water conservation. The resistance of the massive quartz porphyries to erosion has caused a sharp constriction in the channel of the Queanbeyan River at a point downstream from the wide valley occupied by the slates. This constriction forms a steep-sided gorge, reduces the cross section of the stream and renders possible the construction of a wall of relatively small dimensions. Furthermore, the solidity of the quartz-porphyries provides foundations of the utmost stability. There need be no fear that such foundations will either give way or leak. The river runs across the ‘grain’ and the foundations are occupied only by the extremely competent quartz prophyries.

A scheme for constructing a dam on this site, 30.5m high, was reported upon by the Parliamentary Standing Committee in March, 1915.1 Amongst the objects stated to be attained by the work was —

To reduce the volume of flood waters of Canberra Plains during heavy rainfall on the Queanbeyan catchment area. As seen from its dimensions the dam is designed as an overshot weir and the capacity of the storage is given with the water level to the top of the wall, the only flood relief it could afford would be when a flood occurred after a long dry period and the reservoir was partly depleted. The Public Works Committee approved of the proposal to construct the reservoir, but did not consider the work ‘urgent or immediately necessary’.

The Molonglo Floods Committee in their report of 16 March, 1927, recommended the construction of a dam with a height of 45.7m the top of the wall being at RL674 and the spillway at RL654. Their suggestion carried the provision of permanent storage behind the wall to RL634 and above this level the dam to serve for flood retardation purposes only. The total capacity of the storage at the spillway level was taken as 67,800 megalitres and deducting the permanent storage of 11,200 megalitres the capacity available for the storage of flood water would be 56,600 megalitres which would have held up to 1925 flood discharge down the Queanbeyan for 12 1/2 hours. The Molonglo being a shorter river than the Queanbeyan the peak of the flood on the Molonglo is generally ahead of the peak on the Queanbeyan, and the retardation at Googong would allow for subsidence in the Molonglo before the Queanbeyan waters joined it.

An attached drawing showed a design of a straight dam with floods controlled by spillways and sluices.

In an NCDC, report of September 1969 (Canberra Water Supply — Further Augmentation) a wide range of potential sources for future supplies to Canberra was examined including both storage proposals and run-of-river schemes. These included:

  • Googong Reservoir, Queanbeyan River
  • Tennent River on the Gudgenby River
  • Coree on the Cotter
  • Pumping from the Murrumbidgee at Tharwa
  • Extensions of the above Tharwa scheme with 4 alternative storages
  • Use of the Goodradigbee River
  • A Murrumbidgee/Cotter diversion near Tantangara

From all these possible schemes Googong was selected as having the following advantages:

  1. Some additional storage is desirable before introducing a run of river scheme.
  2. Value is seen in having storage in two different catchments each responsive in two different weather conditions.
  3. A storage is a valuable safeguard against pollution due to the die away of bacteria in the stored body of the water.
  4. The Commonwealth has paramount rights over the water in the Queanbeyan River.
  5. The Googong storage scheme has been most extensively studied drawing on hydrological records going back to 1911.

Thus the dam which for so long had waited in the wings at last became central on the stage.

The design and construction of Googong Dam is well documented in departmental reports and in a submission by the contractors for a construction achievement award in 1978. The following outlines the main features of the dam and records a notable experience during the construction phase.

Googong Dam is located in a short gorge section of the Queanbeyan River approximately 9 kilometres upstream of Queanbeyan. The Dam consists of an earth rock fill embankment protected by an adjacent spillway.

The water level at Googong has been set at RL663m to provide a reservoir storage of 119 x 106m3. The bulk water supply distribution system has sufficient flexibility that an equivalent population of 450,000 persons can be supplied at unrestricted consumption from the combined Googong and Cotter systems. Googong also contains additional storage for maintaining the level of Lake Burley Griffin during a dry period, and some irrigation and the riparian requirements downstream of the dam.

The maximum probable flood inflow for the reservoir, 4,530 cumecs was calculated by the hydrometeorological method using a maximised storm determined by the Bureau of Meteorology together with a unit hydrograph derived from a flood in 1925 at the damsite which had a recurrence interval in the order of 100 years. Flood routing through the reservoir reduces this to maximum probable spillway outflow flood of 4,320 cumecs.

The geology of the damsite was first investigated in detail in 1929 for the possible construction of a concrete gravity dam. The adits and shafts which formed part of this investigation were still visible on the site. In 1955 geological investigations of a preliminary nature were carried out for use in comparison studies between the Googong and Bendora sites for a dam. In 1962, further investigations were carried out to select either the Googong or Corin sites.

The partly completed
Fig. 4.10: The partly completed earth and rockfill Googong embankment being overtopped in 1976. The flood rose higher
and carried away the tree in the foreground. Photo — NCDC.

Further geological investigations were carried out in 1970 concurrently with the engineering feasibility studies for various types and arrangements of dams on the Googong site. The final design geological investigations for an earth-rockfill dam with a side spillway incorporating the rock quarries, followed on from these feasibility studies and commenced in mid-1972.

In the Googong area the local rock consists of near vertical beds of dacite with meta-sediment lenses all of middle Silurian age, known as the Colinton Volcanics, Granites of Siluro-Devonian age had intruded in the northern section of the area.

No major fault zone was detected on the dam site, however, fracture zones and associated deep weathering exist in the dacite possibly caused by the intrusive effect of the granite and associated hydrothermal activities.

The embankment is founded mainly on dacite, although the downstream toe and the higher levels of the left abutments are on granite. Although the foundation rock is intensely fractured and jointed, no major zones of high permeability were revealed by pressure testing in the diamond drill holes.

Owing to the proximity of a large centre of population, Queanbeyan, downstream of the dam and the large flood flows that can occur on the river a detailed study was carried out for river diversions.

Hydrological studies indicated that flood probabilities were considerably reduced in the dryer September to March period of the year. For this reason it was considered necessary to construct the bulk of the main embankment in this period.

It was considered neither practical nor necessary to construct a river diversion system without utilizing possible overtopping of the uncompleted embankment by large floods. Adequate reinforcement of the downstream slope was carried out to prevent shallow slips and unravelling of the surface rockf ill during overtopping.

In October 1976 the partially completed dam was subjected to a severe flood. The account of this experience prepared by Thiess Bros. Pty Ltd, the contractors for the project provides an excellent summary.

As aforesaid, the 6 months period from 1/9/76 to 1/3/77 was regarded as the “dry” period of the year, of minimum flood risk, and as such was selected by the designers for the construction of the “critical section” of the embankment between RL620 and RL665. It was therefore expected that weather conditions would be favourable and that after the successful completion of the first stage embankment construction on target date, the embankment construction progress would not be further adversely affected.

As it happened, the 1976 year proved to be an exceptional year.

On the morning of Friday, 15 October, 1976, the Bureau of Meteorology issued a confidential alert of possible flood producing rains over the Googong Catchment Area. The embankment fills were completed at this stage to RL627 in the core and upstream rockfill sections, the downstream rockfill section was completed to RL630. The RL630 layer of downstream slope reinforcement protection was at the time 75 per cent complete, and the top of the embankment fill was 140m wide at this point of construction.

NCDC and Departmental
Fig. 4.11: NCDC and Departmental observers watching the Googong embankment being overtopped on 16 October 1976.

In the afternoon, after further warning, an instruction was issued by the Superintending Resident Engineer to put the Contractor’s workforce on standby for the night and for the weekend, and to complete the uncompleted 25 per cent of the downstream slope protection reinforcement if required. The workforce of approximately 30 men and staff was called Out for this purpose at 5.00 am on Saturday morning, and worked until the embankment over-topped, at 10.25 am. The protective reinforcement had been completed as required by this time.

Prior to that, all construction plant was moved from the low lying areas and secured, except for two draglines used for excavation of materials from the sand and gravel deposits of the site of the dam. Access to these became impossible immediately after the river started to rise.

The embankment was overtopped completely at 10.25 am on Saturday morning. This first overflow lasted 17.5 hours, and the maximum depth of flow over the crest in the first peak was 2.5m, which represents an overflow of some 550 cubic metres per second, and with 220 cubic metres per second of additional flow through the diversion tunnel this was a flood of approximately one in one hundred year frequency for the October/ November period of the year.

This first overflow ceased at approximately 4.00 am on Sunday. The second overflow began at 9.20 am on Sunday 17 October, and ceased at 1.20 am on Monday the following morning. This second peak had a maximum depth of 1.5m over the crest, which represents a flow of some 200 cubic metres per second. During both peaks, the 5m diameter diversion tunnel was running full with a flow of 220 cubic metres per second.

Between the overflows, from 2.00 am to 9.20 am, an inspection showed that the downstream slope protection reinforcement was still in generally good condition. In a section of the crest, a channel section of 4m long, 2m wide and 1m deep, had eroded in the top layer of the reinforced rockfill. Work commenced immediately to repair it. Also, several sections of rock were repacked behind the adjacent mesh, and debris caught on the crest were removed. Also some loosened reinforcing bars were rewelded.

After the second over-topping, work recommenced on the repairs to the protective work, debris removal and rock packing on the face.

Shortly after midday on Monday, 18th October, 1976, a further 24 hour flood warning was issued and the repair work had to be accelerated. Immediate steps were taken to ensure that work would continue through the night. Preparation commenced for concreting areas of washed out rock on the downstream rock face. Additional agitator trucks, concrete pumps, welding sets and lighting generators were hired and arrangements made for night-time deliveries of cement and aggregates. The earth drain above the downstream tunnel portal was converted to a haul road to permit truck access on the embankment, enabling concreting of cavities in the downstream embankment face to commence by 3.15 pm on Monday. From that time, mesh and rebar repairs on the armour, and concrete repairs to the downstream face continued non-stop until 6.00 am the following morning. Some 70 sheets of mesh were placed and welded and 154 cubic metres of concrete placed to damaged sections of the downstream face during this period. The third overflow did, however, not occur.

Specific requirements for diversions and related embankment construction included:

  1. A diversion tunnel of 5m internal diameter together with inlet and outlet channels to be constructed through the left abutment (and concrete lined for later usage in the outlet system).
  2. An upstream coffer dam approximately 12m high with a crest level RL622m and reinforced downstream rock slope.
  3. A downstream coffer dam with a crest level lower than the upstream coffer dam.
  4. Embankment to be protected by steel mesh and bar reinforcement on the downstream slope to RL6S2m, which is about 42m above river bed level.

The embankment section consists of an impermeable earth core protected by filters and enclosed by rock shells in the conventional manner. The core is non-symmetrical about the vertical centreline of the embankment, it is inclined slightly upstream to assist in obtaining acceptable slope stabilities and core contact with the most economical section. A slight steepening (1:1.7 from 1:1.8) of the downstream slope was achieved by this method with its consequent economies in materials.

A secondary embankment was constructed in a low saddle approximately 1/2km north east of the main embankment. This embankment is 13.5m high and 240 metres long.

Landscaped foreshores
Fig. 4.12: Landscaped foreshores of Lake Burley Griffin with Government House (right). Photo — Pieter Arriens for NCDC.

The spillway incorporates the two quarries for embankment rockfill. The upper (dacite) quarry forms the approach channel and the major part of the spillway excavation. The lower (granite) quarry is incorporated into the spillway as an energy dissipating basin.

The spillway consists of the quarry approach channel, concrete crest 124m long, curved in plan, a concrete lined chute 64m long converging to 62m at the lip, an unlined channel in rock and quarry dissipating basin.

By February 1978 Googong Dam was a reality and storage had commenced but as a lake its story had just begun.

Since the time when Googong was first envisaged as a multi purpose reservoir Canberra has grown from a village to a Capital of more than 230,000 people. At the same time despite growing pressures for the conservation of water supply catchments and storages for that sole purpose, public pressure has likewise developed throughout the world for the use of such areas for both water supply and recreation. This has been demonstrated as being practicable with adequate water treatment and controls of land and water use.

The increasing pressure around the world for multiple use of water storages was acknowledged but Googong Dam is primarily a terminal city water supply facility in which the health of the total community must have priority over demands for further recreational areas made by some groups.

After a careful review of this conflict, the Minister for the ACT announced a programme of staged development of recreational facilities with careful monitoring of water quality. When the dam was opened, road access and picnic facilities were made available to areas just downstream of the storage. Construction of roads is also taking place to parts of the storage, well upstream of the outlet tower, including the unusual limestone formation called London Bridge and to the adjacent woolshed and picnic area.

In this dry continent, our National Capital has been developed in picturesque valleys with a backdrop of mountains rising to nearly 2000 metres. In times of drought, many of the streams will cease to flow but this and future generations now have a heritage of lakes and dams which should continue down the decades to add sparkle to the landscape, recreational use for all ages and provide a water supply of assured quantity and quality for Canberra.

References

  1. Selected early reports of the Parliamentary Committee on Public [return] Works include:
    1. 1915 Storage & Regulating Reservoir, Upper Queanbeyan River (Pantry. Paper 1914-15-16 No. 64)
    2. 1916 Dams for Ornamental Waters in Canberra (pp.l914-lS-16 No. 353)
    3. 1926 Construction of Dam and Improvements on the Molonglo River, Federal Capital (No. 37)
    4. 1956 Canberra Community Hospital A.C.T. (pp.1956 No. 35)
    5. 1955 Water Supply Storage System at Canberra A.C.T. (pp.1954-5 No. 52)
    6. 1955 Commonwealth Avenue Bridge, Canberra (pp.1954-S No.53)
  2. Memorandum available on Parliamentary library file 54/14-4. (The Parliamentary Standing Committee on Public Works).
  3. Lake Burley Griffin Australia Paper. Minty A.E. International Symposium on Man Made Lakes, Their Problems and Environmental Effects. Tennessee U.S.A. 1971.
  4. River Model, Spillway Model and Dam Design for the Canberra Lake Scheme. A.J. Condon, B.V. Kearsley and A. Fokkema Journal, Institution of Engineers Australia, September 1964. [return]
  5. An advisory Report on the Landscape of the Canberra Lake Scheme— William Holford and Partners for National Capital Development Commission. [return]
  6. Belconnen Water Feature — Feasibility Study 1967 for National Capital Development Commission. Laurie and Montgomerie. [return]
  7. Upper Cotter Arch Dam Design — KG. Harding B.E. Paper No. 1618, Civil Engineering Transactions September 1962 of Institution of Engineers Australia. [return]
  8. Corin Dam — Design and Construction Report. Commonwealth Department of Works — Canberra Branch — May 1970. [return]
  9. Googong Dam and Appurtenant Works. Entry for Construction Award 1978— Thiess Brothers Pty. Limited.
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