Fish river water supply scheme
Fish river water supply scheme
Facts and history
The Fish River water supply scheme on the NSW Central Tablelands is unique as the only water supply scheme in eastern Australia to transfer western flowing water east of the Great Dividing Range, mostly by gravity.
Started by the Civil Constructional Corps during WWII and expanded in the 1950s and 1960s, the scheme draws water from Oberon Dam and Duckmaloi Weir and includes 236 kilometres of pipelines and a tunnel under the Great Dividing Range.
Today the scheme provides water to Wallerawang and Mount Piper power stations, to Oberon and Lithgow councils for domestic and industry use, and to about 230 properties along its route. It also supplements town supplies in the upper Blue Mountains.
A scheme of firsts
- Only water supply scheme in eastern Australia to transfer western flowing water east of the Great Dividing Range.
- First slab and buttress dam built in NSW built at Oberon, the highest of its type in Australia, and with the largest volume of water of any slab and buttress dam in Australia.
- First and still the longest pre-stressed concrete water supply pipeline in Australia is the scheme’s 54-kilometre long pipeline from Oberon to Wallerawang.
- Greatest pressure in any water supply pipeline in Australia on the scheme’s 40 kilometre long steel pipeline to Katoomba where it climbs a 250-metre high cliff from the Megalong Valley to Narrow Neck Peninsular.
Why the scheme was built
The Fish River water supply scheme has its origins in chronic water supply problems in the towns of Lithgow, Wallerawang, Portland and Oberon, which were exacerbated by the 1940s drought. Small local schemes were rejected in favour of a regional scheme but funding shortages delayed the start of work.
World War II and the need for Australian-sourced fuel secured Commonwealth Government funding to re-start the project in 1943 with an expanded scope to include water supply to the Glen Davis shale oil works. Initial construction was by the Civil Constructional Corps, established in 1942 to supply labour for wartime infrastructure projects such as airfields, roads and barracks.
The early 1950s saw the closure of the shale oil works but the creation of new power stations for electricity generation at Wallerawang. The power stations’ need for cooling water, and increasing domestic demand in the upper Blue Mountains where there were frequent water restrictions, was the catalyst for the scheme’s expansion in the 1950s and 1960s.
Today the scheme supplies water to Wallerawang and Mount Piper power stations, to Oberon and Lithgow councils for domestic and industry use, and to about 230 properties along its length. It also supplements town supplies in the upper Blue Mountains.
How it worked in 1949 ... and then in 1964
Stage 1 (1943-49)
- Reliable rainfall and an elevation more than 1000 metres above sea level make Oberon an ideal location for a regional water supply scheme to operate largely by gravity.
- A slab and buttress dam is built on the Fish River just south of Oberon, constructed to a height of 21.3 metres but with foundations and buttress bases to allow later raising of the dam wall.
- A 105-kilometre pipeline from Oberon Dam through Wallerawang and Portland to the shale oil works at Glen Davis.
- A 15-kilometre branch pipeline from Wallerawang to Lithgow.
- A pump station and water main to Oberon town reservoir.
Stage 2 (1954-59)
- Raising Oberon Dam wall and outlet tower from 21.3 metres to its full design height of 33.5 metres, and building a ski jump spillway into the dam wall.
- A new pipeline from Oberon to Wallerawang to service the new power station.
- A break-pressure tank near Duckmaloi to combine flows from Oberon and the future Duckmaloi Weir and to control pressure in downstream pipeline.
- A small dam at Rydal to ensure reliable supply to the power stations.
- A small reservoir at Lidsdale as an emergency supply and a fire-fighting source for the power station.
- A connection for the future pipeline to the Blue Mountains.
Stage 3 (1961-64)
- A 1.1-kilometre long tunnel at Hampton under the Great Dividing Range, 44 metres under the surface at the range’s highest point.
- A 40-kilometre long pipeline connecting the scheme to Cascade Dams at Katoomba.
- A small weir on the Duckmaloi River.
How the scheme was built – stage 1
Work on the Fish River water supply scheme began in 1943 by the Civil Constructional Corps. The corps comprised mainly men aged in their 30s and 40s who were too old to serve in the armed forces but who were conscripted to build wartime infrastructure. They received pay based on civilian award rates but their work was highly regulated; they could not strike and might be sent anywhere in Australia.
Oberon Dam’s slab and buttress design was adopted partly because of the availability of this relatively cheap labour, and also due to the wartime shortage of earthmoving equipment need to build an earth-fill embankment dam. Oberon became the first slab and buttress dam in NSW, and when raised to its maximum design height of 33.5 metres in 1957, it became the largest such dam in Australia.
Five construction camps were established at Oberon Dam, Duckmaloi, Tarana, Wallerawang and Coco Creek near Glen Davis. Each camp had 150-280 men and was organised on a similar layout to military camps with prefabricated buildings, generally semi-cylindrical Nissen Huts, including a kitchen/mess, welfare/canteen, medical/administration, ablutions, drying room and barrack-style accommodation blocks.
The Oberon Dam work site also included a railway siding, concrete batching plant with flying fox and workshops for blacksmiths, plumbers, riggers, machinists and carpenters.
Workers endured winter temperatures as low as minus eight degrees Celsius. Most of the excavation for the 105-kilometre pipeline from Oberon to Glen Davis was done by hand because the terrain was so steep and rugged.
Following the disbandment of the Civil Constructional Corps in 1945, many ex-members remained working on the Fish River scheme as contract labourers. Oberon Dam was largely completed by 1947 but finishing work on stage 1 continued until 1949 when the last houses in Glen Davis were connected.
The campsites were dismantled and moved to other locations when work was completed. Only one of the Nissen Huts remains at Oberon Dam, just behind the dam wall.
How the scheme was built – stages 2 & 3
Work on stage two began in 1954. The Oberon Dam wall and outlet tower was raised to its current height of 33.5 metres, and a new ski jump spillway added.
Much of the equipment used on stage 1 was still on site and was re-used. A construction camp of 50 pre-fabricated cottages and living quarters for 100 single men was established nearby.
The original design was for slab and buttress construction across the entire length of raised wall. A cheaper earth-fill embankment was instead built on the left abutment thanks to the now ready availability of earthmoving equipment after the war. The raised dam was completed in 1957.
Stage 2 of the scheme’s expansion also included construction of a new 54-kilometre long pipeline from Oberon to Wallerawang to service the new power station. Pipeline construction began in 1957 and finished in 1959.
The contract was so large that a special pipe manufacturing plant was built at Lithgow. There 10,000 pipes were built for what became the longest pre-stressed concrete water supply pipeline in Australia.
Work on stage 3 began in 1961. It involved extending the Fish River scheme to communities in the upper Blue Mountains.
In a major change to the original concept, a tunnel was built under the Great Dividing Range at Hampton so that water could be supplied by gravity from Oberon to Katoomba via a 40-kilometre long steel pipeline connecting the Fish River scheme to the Cascade Dams.
The 2.1 metre high by 1.2 metre wide Hampton tunnel was excavated using the drill and blast method. Its 1.1-kilometre length is 44 metres under the surface at the range’s highest point.
The steel pipeline is notable for the pressure it withstands during a 250-metre climb from the Megalong Valley to Narrow Neck Peninsular, a section which includes a 30-metre vertical pipe attached to the rock face.