A series of severe droughts in Sydney region led to the construction of the Warragamba Dam. Sydney's initial fresh water came from the
Tank Stream, but as Sydney continued to grow the water was often in short supply and polluted.
In 1869 a member of the Commision of Inquiry, Lieutenant Thomas Moore, recommended the construction of a 52 metre high masonry
dam on the Warragamba River. The scheme was judged economically and technically impracticable.
Successive droughts in the period 1897-1902 again brought investigation into the feasibility of a dam on the River but again was
abandoned. However in the prolonged drought of 1904-1910 interest was revived and by 1919 a site for a large dam had been selected.
In the meantime the Cataract, Cordeaux, Avon and Nepean Dams continued to be developed as a major source for Sydney.
In 1934-1942 Sydney experienced its longest drought and Sydney's 1.5 million people were left with only 15 months water supply.
Restrictions were severe and strictly enforced. At one stage only 6 weeks water supply remained. There was no time to build a large dam
so the Sydney Water Board decided to build a weir on the river and pumping the water through a temporary pipeline to Prospect Reservoir.
This was called Stage 1 "Warragamba Emergency Scheme"
This took 18 months to complete commencing in 1938 and completed in 1940, delivering 180 mega litres daily and provided sufficient
water until the drought broke in May 1941.
The outbreak of World War II further deferred major construction until work finally commenced in 1948. Two coffer dams were built and a
300 metre concrete lined tunnel 5.5 metres wide by 4.2 metres high was built on the eastern side. The diversion tunnel was capable of
carrying up to 6.15 million litres a minute.
Floods were a problem. High volumes of flood waters spilling over a dam had disastrous effects. A smooth concrete floor or apron with
smooth training walls on either side has been built on the downstream side of the dam to contain flood waters.
Excavation of the site commenced in 1948 and continued for 5 years. Over 2.3 millions tonnes of rock were removed. Flood left
tremendous amounts of silt and debris with up to 90,000 cubic metres of deposits being excavated after each flood. In 1956 there was 14
separate floods, delaying constructions.
The first concrete was poured in June 1953 and continued for 24 hours a day until the project was completed in 1960. More than 2,550,00
tonnes of sand and gravel were needed. This was obtained from the Nepean River near Penrith and delivered to the dam site by a series
of 600 buckets, each holding 1,250kg via a aerial ropeway and at 30 second intervals.
The design of placing concrete, together with the block construction, resulted in Warragamba Dam being crack free. There are five crest
gates installed to start to operate automatically when water rises 75mm above the full supply level. The water falls 100 metres into the
stilling pool at a rate of 12.7 mega litres per second. A hydro electric power station was designed as an integral part of the dam using
surplus water to supply 50 megawatts of electricity into the State grid system. This no longer operates.
Between 1987 and 1989 the dam wall was raised 5 metres and strengthened using post tensioned steel cables and tying the upper portion
of the wall to its base. This was the first step in a two stage solution to strengthen the dam in case of the 1 in 1000 year flood.
Work began on stage two of the safety program in 1999. This involved the construction of an auxiliary spillway o the eastern bank of the
dam. This was completed in 2002 and is designed to allow floodwater to pass safely around the dam and reduce pressure on the dam
wall.
Although Warragamba Dam is closed to the public today due to upgrades to the dam and recreational facilities, we welcome visitors to
view the Dam via the viewing platform and learn more from the information Centre located in the picnic grounds on Farnsworth Avenue.
Have a picnic in the picnic grounds which toilets, provide hot water, electric BBQ's and covered tables.
The Sydney Catchment Authority have planned for the new picnic grounds and the new visitor centre/viewing platform to be opening in
2008. Click here to read Media Release about New Visitor Centre.
Warragamba Dam and Lake Burragorang
● Warragamba Dam is Sydney's largest water supply dam
● The dam is made of concrete and took twelve years to build from 1948 to 1960
● Lake Burragorang, which formed behind the dam, hold about 4 times more water than Sydney Harbour
● It accounts for about 80% of the available water supply for the Sydney region
● Water to fill the lake drains from a catchment area of over 9000 square kilometres
● When the lake is too full after heavy rain, water is released automatically down the central spillway of the dam. The water flows down the
Warragamba River into the Hawkesbury - Nepean River and eventually enters the sea at Broken Bay
● A new spillway was completed in 2002 to protect the dam from extreme floods.
WARRAGAMBA DAM FACTS
Height: 142 metres, Length: 351 metres, Thickness at top: 8.5 metres, Thickness at base: 104 metres, Width of central spillway: 90
metres, Width of auxilary spillway (at mouth): 190 metres, Length of auxiliary spillway: 700 metres.
LAKE BURRAGORANG FACTS
Total capacity (when full): 2 031 000 megalitres, Area: 75 square kilometres, Length of lake: 52 kilometres, Length of foreshores: 354
kilometres, Maximum depth of lake: 105 metres, Catchment area: 9051 square kilometres, Average Annual rainfall: 840 millimetres.
