Canning Dam
Encyclopedia
The Canning Dam and reservoir provide a major fresh water resource for the city of Perth, Western Australia
. The dam
is situated on the Darling Scarp
and is an impoundment of the Canning River
. It is noted for its innovative structural and hydraulic design that was considered to be at the forefront of concrete gravity dam design at the time of construction. The Canning Dam was Perth's primary water supply up until the 1960s when other sources of fresh water were tapped. Currently the dam supplies approximately 20 percent of Perth's fresh water. Inflow into the Canning Reservoir is estimated to be 22 GL and has a storage capacity of 90352 megalitres (23,868,471,912.7 US gal).
Since its completion in 1940, the Canning Dam has contributed to a wide range of environmental and ecological problems in surrounding regions, problems include more common algal blooms, habitat loss and sedimentation
. Despite these issues, Canning Dam and the adjacent parks and forests provide a variety of recreational activities for the public such as bushwalking, historic walks and picnic facilities.
in the 1930s.
In 1924 a small pipehead dam was built 6 kilometres (4 mi) downstream from the present Canning Dam. It was only intended as a quick fix to the water supply problem and it soon became apparent that a major reservoir was needed, although it would be nine years before work on the current Canning Dam would begin. The new dam was completed in 1940 at a cost of AU£
1.1 million. Engineer Russell Dumas
designed the dam and directed most of its construction.
A further improvement was made in 1951 when a concrete-lined channel was constructed to divert stream flow from the nearby Kangaroo Gully catchment. The Canning Dam and reservoir was Perth's primary source of water until the boom growth of the city in the 1960s and the completion of Serpentine Dam in 1961.
In 1975 the reservoir was connected to Perth's Integrated Water Supply Scheme by the Canning Tunnel
. Prior to its opening water had flowed through the Canning Contour Channel
to Gosnells
.
The Canning Dam and reservoir still supplies approximately 20 percent of Perth's drinking water requirements and plays an important role in the context of the development of Perth.
The Canning reservoir is also used to store water from the newly completed Kwinana Desalination Plant
. Treated water can be pumped from the plant to the reservoir through the new Forrestdale Pumping Station.
which forms part of an Archaean Shield composed largely of granite
with some invaded linear belts of metamorphosed sedimentary and volcanic rocks.
The dam wall is situated in a narrow gorge running east and west, with rock sides sloping upward from the river bed. Behind the dam wall, the south branch of the Canning River joins the main stream, with the impounded water forming a lake which stretches back in three major arms to the east south-east and south.
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The catchment has an area of 804 square kilometres (310.4 sq mi). The reservoir is at 200 metres (656.2 ft) AHD
and the highest point of the catchment, Mount Cooke is at 582 metres (1,909.4 ft) AHD.
Climatically, the area receives about 900 millimetres (35.4 in) of rainfall per annum with most of this falling between May and September. There is widespread variability of rainfall across the catchment however, from between 700 and 1300 mm (27.6 and 51.2 ).
Since 1975 long-term average rainfalls at the dam wall have decreased by 20 percent and streamflow into the catchment by approximately 60 percent—the average annual inflow between 1948 and 1974 was 52 GL which had reduced to 22 GL between 1975 and 2004.
The construction of Canning Dam ended a long period during which Perth's water supply was generally unsatisfactory in quality (either due to salinity
or bacterial pollution or both) and in quantity. The project, the biggest public works program of the decade, stimulated significant growth in the local economy and provided desperately needed work for around five hundred men.
Several innovative design concepts and construction methods which were new to Australia were introduced on the project, while others which were used on the nearby Wellington Dam, were improved upon at the Canning dam site.
At the Canning Dam and indeed all dams, care had to be taken to prevent water seepage between the foundation rock and the structure of the dam. At the Canning in addition to cutting back the foundation to solid unfractured rock, a cut-off trench was sited near the upstream face of the dam, down stream which a rock filled drain containing open jointed pipes was provided to intercept any seepage between the rock face and the concrete of the dam. The inclusion of an internal drainage system was considered innovative at the period. Near vertical tubular 8 in (200 mm) cut-off drains were provided at five-foot (1.52 m) intervals along the dam to relieve internal seepage through the concrete.
While state of the art materials-handling methods were used, in some instances labour-saving machinery worked beside operations intended to maximise the labour content. Sustenance workers were employed chiefly for on-site preparation, road construction, foundation excavation, clearing timber from the reservoir basin, and on some concreting operations. Skilled workers were required on the dam for fixing the formwork
where the concrete was poured. These workers were probably employed at normal day labour rates, the main employment method used on the project. Bulk handling of cement was also used for the first time in Australia, this saw a significant saving as opposed to bagged cement which was the standard practice of the day.
Generally construction work proceeded smoothly and from an engineering point of view there were few setbacks. However, one did occur in the early stages of construction. In March 1934 there was a violent storm bringing 130 mm (5.12 in) of rain in less than two days. As a result the river rose rapidly which flooded the dam foundation workings. Pumps had to be installed and work resumed three days later.
The dam was completed in September 1940. When built it was the longest concrete gravity dam in Australia, and also the second highest after the Burrinjuck Dam
in New South Wales. As of 1997 of the 90 large concrete and masonry gravity dams in Australia the Canning Dam is still the fifth highest and the sixth longest. It is the largest concrete dam in Western Australia in terms of length of crest and volume of concrete.
The final cost of the dam was significantly less than had been originally budgeted for, and the work was completed on schedule to a date that was calculated seven years previously.
) in the concrete. AAR results in swelling of the concrete, which may cause secondary compressive stresses, localized map cracks, and, ultimately structural cracks. In addition, the concrete tensile strength
and elasticity
significantly decreases. Many old concrete dams are known to suffer from AAR, including Fontana Dam
in Tennessee and Pian Telessio dam in Italy among others.
Extensive remedial works were undertaken between 1999 & 2001 to strengthen the dam wall. This work involved removing the top 3.8 m (12.5 ft) of the existing dam wall and drilling/blasting through the dam wall plus up to a further 70 m (229.7 ft) into the bedrock below. The top section of the wall was then rebuilt using reinforced concrete. Finally, permanent, re-stressable ground anchors were then installed through the formed and drilled holes from the crest to be stressed and grouted into the foundation rock. At time of completion, these were the largest capacity and longest permanent ground anchors ever installed in the world.
An innovative drilling and blasting technique called Penetrating Cone Fracture (PCF) was used in the remedial works process. PCF was chosen over conventional drilling and/or blasting techniques due to the reduced risk of damage to the existing structure from vibration, as well as lower noxious fume and dust levels.
supply dams, water flow into the Canning River
has been reduced by up to 96%. A number of freshwater fish species which are endemic to the south-west of Western Australia are found in the Canning River system, however studies of fish and fish habitats in the area have shown that fish numbers are low due to a loss of habitat and a loss of linkage between breeding areas due to low flows, preventing fish migrating upstream and reaching important breeding and nursery grounds. Stagnant water caused by a lack of water flow has provided a suitable habitat for successful breeding of an introduced pest, the Mosquitofish
.
Damming of the Canning caused dramatic flow reductions that significantly altered downstream aquatic macroinvertebrate communities. The lack of water flow has also resulted in a poor flushing effect below the dam wall. An excessive amount of nutrients from fertilizers and animal waste has caused algal blooms and eutrophication
.
Many river pools which are an important summer refuge and habitat for aquatic and terrestrial flora and fauna have been lost due to sedimentation
and modification of the flow regime caused by impoundments in the Canning River.
Periodic flooding of the Canning River from the dam is required to disperse seed, stimulate germination and ensure seedlings survive, recharge shallow groundwater tables that are important during periods of drought and to discourage and prevent weed growth. However during times of low rainfall periodic flooding is reduced.
s), look outs and historic walks - many with disabled access. Bushwalking occurs throughout the catchment, particularly along the Bibbulmun Track
, which passes through the catchment about 10 km upstream of Canning Dam. Several mountain bike
trails run either through the Canning National Park or adjacent State Forest areas.
The Canning Reservoir, Canning River and tributaries are illegally fished for marron
, especially during summer. Boating, fishing and swimming are prohibited in the reservoir for health and hygiene reasons. Unauthorised camping (including overnight stays and/or outside of designated areas) and unauthorised trail establishment occur more and more frequently in the Canning catchment. Unauthorised vehicle access, illegal fishing and pig hunting also occur. Such activities represent a significant risk to water quality.
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
. The dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
is situated on the Darling Scarp
Darling Scarp
The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north-south to the east of the Swan Coastal Plain and Perth, Western Australia...
and is an impoundment of the Canning River
Canning River (Western Australia)
The Canning River is a major tributary of the Swan River in south western Western Australia.-Source and route:With headwaters on the Darling Scarp, the Canning meanders through suburbs of Perth on the Swan Coastal Plain, including Cannington, Thornlie, Riverton, Shelley, Rossmoyne and Mount...
. It is noted for its innovative structural and hydraulic design that was considered to be at the forefront of concrete gravity dam design at the time of construction. The Canning Dam was Perth's primary water supply up until the 1960s when other sources of fresh water were tapped. Currently the dam supplies approximately 20 percent of Perth's fresh water. Inflow into the Canning Reservoir is estimated to be 22 GL and has a storage capacity of 90352 megalitres (23,868,471,912.7 US gal).
Since its completion in 1940, the Canning Dam has contributed to a wide range of environmental and ecological problems in surrounding regions, problems include more common algal blooms, habitat loss and sedimentation
Sedimentation
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...
. Despite these issues, Canning Dam and the adjacent parks and forests provide a variety of recreational activities for the public such as bushwalking, historic walks and picnic facilities.
History
Development of the Canning River as a source of water for Perth was first proposed in a report of the first Metropolitan Water Works Board of Perth in 1896. Investigation of the site began in 1897 when engineer Thomas Hodgson surveyed and proposed the dam's current location as a possible site. However despite the recommendations of further inquiries, and an extreme shortage of water in some years, government funds were not allocated for the construction of a dam until the Great DepressionGreat Depression
The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...
in the 1930s.
In 1924 a small pipehead dam was built 6 kilometres (4 mi) downstream from the present Canning Dam. It was only intended as a quick fix to the water supply problem and it soon became apparent that a major reservoir was needed, although it would be nine years before work on the current Canning Dam would begin. The new dam was completed in 1940 at a cost of AU£
Australian pound
The pound was the currency of Australia from 1910 until 13 February 1966, when it was replaced by the Australian dollar. It was subdivided into 20 shillings, each of 12 pence.- Earlier Australian currencies :...
1.1 million. Engineer Russell Dumas
Russell Dumas
Sir Russell John Dumas KBE, CMG was a public servant and engineer who led several large works projects in Western Australia.-Early life:Dumas was born in Mount Barker, South Australia to a family of five children...
designed the dam and directed most of its construction.
A further improvement was made in 1951 when a concrete-lined channel was constructed to divert stream flow from the nearby Kangaroo Gully catchment. The Canning Dam and reservoir was Perth's primary source of water until the boom growth of the city in the 1960s and the completion of Serpentine Dam in 1961.
In 1975 the reservoir was connected to Perth's Integrated Water Supply Scheme by the Canning Tunnel
Canning Tunnel
The Canning Tunnel was constructed between 1973 and 1975 to link Canning Dam to Perth's Integrated Water Supply System. It was built to replace the Canning Contour Channel which was a depression era public works project of the 1940s and constructed in conjunction with the opening of the dam.The...
. Prior to its opening water had flowed through the Canning Contour Channel
Canning Contour Channel
The Canning Contour Channel is a series of made-made concrete channels and steel and cast iron pipelines in the Darling Scarp in Western Australia constructed between July 1935 and December 1936...
to Gosnells
Gosnells, Western Australia
The City of Gosnells is a Local Government Area in the southeastern suburbs of the Western Australian capital city of Perth, located northwest of Armadale and about southeast of Perth's central business district...
.
The Canning Dam and reservoir still supplies approximately 20 percent of Perth's drinking water requirements and plays an important role in the context of the development of Perth.
The Canning reservoir is also used to store water from the newly completed Kwinana Desalination Plant
Kwinana Desalination Plant
The Kwinana Desalination Plant, located south of Perth, Western Australia, turns seawater from Cockburn Sound into nearly 140 megalitres of drinking water per day, supplying the Perth metropolitan area....
. Treated water can be pumped from the plant to the reservoir through the new Forrestdale Pumping Station.
Hydrology
The Canning Dam Catchment lies within the Darling ScarpDarling Scarp
The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north-south to the east of the Swan Coastal Plain and Perth, Western Australia...
which forms part of an Archaean Shield composed largely of granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
with some invaded linear belts of metamorphosed sedimentary and volcanic rocks.
The dam wall is situated in a narrow gorge running east and west, with rock sides sloping upward from the river bed. Behind the dam wall, the south branch of the Canning River joins the main stream, with the impounded water forming a lake which stretches back in three major arms to the east south-east and south.
Australian Height Datum
The Australian Height Datum is a geodetic datum for altitude measurement in Australia. According to Geoscience Australia, "In 1971 the mean sea level for 1966-1968 was assigned the value of zero on the Australian Height Datum at thirty tide gauges around the coast of the Australian continent...
and the highest point of the catchment, Mount Cooke is at 582 metres (1,909.4 ft) AHD.
Climatically, the area receives about 900 millimetres (35.4 in) of rainfall per annum with most of this falling between May and September. There is widespread variability of rainfall across the catchment however, from between 700 and 1300 mm (27.6 and 51.2 ).
Since 1975 long-term average rainfalls at the dam wall have decreased by 20 percent and streamflow into the catchment by approximately 60 percent—the average annual inflow between 1948 and 1974 was 52 GL which had reduced to 22 GL between 1975 and 2004.
Construction
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
or bacterial pollution or both) and in quantity. The project, the biggest public works program of the decade, stimulated significant growth in the local economy and provided desperately needed work for around five hundred men.
Several innovative design concepts and construction methods which were new to Australia were introduced on the project, while others which were used on the nearby Wellington Dam, were improved upon at the Canning dam site.
At the Canning Dam and indeed all dams, care had to be taken to prevent water seepage between the foundation rock and the structure of the dam. At the Canning in addition to cutting back the foundation to solid unfractured rock, a cut-off trench was sited near the upstream face of the dam, down stream which a rock filled drain containing open jointed pipes was provided to intercept any seepage between the rock face and the concrete of the dam. The inclusion of an internal drainage system was considered innovative at the period. Near vertical tubular 8 in (200 mm) cut-off drains were provided at five-foot (1.52 m) intervals along the dam to relieve internal seepage through the concrete.
While state of the art materials-handling methods were used, in some instances labour-saving machinery worked beside operations intended to maximise the labour content. Sustenance workers were employed chiefly for on-site preparation, road construction, foundation excavation, clearing timber from the reservoir basin, and on some concreting operations. Skilled workers were required on the dam for fixing the formwork
Formwork
Formwork is the term given to either temporary or permanent molds into which concrete or similar materials are poured. In the context of concrete construction, the falsework supports the shuttering moulds.-Formwork and concrete form types:...
where the concrete was poured. These workers were probably employed at normal day labour rates, the main employment method used on the project. Bulk handling of cement was also used for the first time in Australia, this saw a significant saving as opposed to bagged cement which was the standard practice of the day.
Generally construction work proceeded smoothly and from an engineering point of view there were few setbacks. However, one did occur in the early stages of construction. In March 1934 there was a violent storm bringing 130 mm (5.12 in) of rain in less than two days. As a result the river rose rapidly which flooded the dam foundation workings. Pumps had to be installed and work resumed three days later.
The dam was completed in September 1940. When built it was the longest concrete gravity dam in Australia, and also the second highest after the Burrinjuck Dam
Burrinjuck Dam
Burrinjuck Dam is a high, concrete gravity dam on the Murrumbidgee River approximately 60 km from Yass, New South Wales, Australia. The Yass and Goodradigbee Rivers flow into the dam. The dam divides the upper and lower catchment of the Murrumbidgee and is the headwater storage for the...
in New South Wales. As of 1997 of the 90 large concrete and masonry gravity dams in Australia the Canning Dam is still the fifth highest and the sixth longest. It is the largest concrete dam in Western Australia in terms of length of crest and volume of concrete.
The final cost of the dam was significantly less than had been originally budgeted for, and the work was completed on schedule to a date that was calculated seven years previously.
Remedial works
Recently the Canning Dam has been subjected to considerable cracking of the upper parts of the dam and upper gallery. Investigations have shown that cracking was due to strong AAR (alkali aggregate reactivityAlkali-aggregate reaction
Alkali–aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates...
) in the concrete. AAR results in swelling of the concrete, which may cause secondary compressive stresses, localized map cracks, and, ultimately structural cracks. In addition, the concrete tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
and elasticity
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....
significantly decreases. Many old concrete dams are known to suffer from AAR, including Fontana Dam
Fontana Dam
Fontana Dam is a hydroelectric dam on the Little Tennessee River in Swain and Graham counties, North Carolina, USA. The dam is operated by the Tennessee Valley Authority, which built the dam in the early 1940s to accommodate the skyrocketing electricity demands in the Tennessee Valley at the...
in Tennessee and Pian Telessio dam in Italy among others.
Extensive remedial works were undertaken between 1999 & 2001 to strengthen the dam wall. This work involved removing the top 3.8 m (12.5 ft) of the existing dam wall and drilling/blasting through the dam wall plus up to a further 70 m (229.7 ft) into the bedrock below. The top section of the wall was then rebuilt using reinforced concrete. Finally, permanent, re-stressable ground anchors were then installed through the formed and drilled holes from the crest to be stressed and grouted into the foundation rock. At time of completion, these were the largest capacity and longest permanent ground anchors ever installed in the world.
An innovative drilling and blasting technique called Penetrating Cone Fracture (PCF) was used in the remedial works process. PCF was chosen over conventional drilling and/or blasting techniques due to the reduced risk of damage to the existing structure from vibration, as well as lower noxious fume and dust levels.
Environmental issues
Since the construction of the Canning Dam, among other drinking waterDrinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
supply dams, water flow into the Canning River
Canning River (Western Australia)
The Canning River is a major tributary of the Swan River in south western Western Australia.-Source and route:With headwaters on the Darling Scarp, the Canning meanders through suburbs of Perth on the Swan Coastal Plain, including Cannington, Thornlie, Riverton, Shelley, Rossmoyne and Mount...
has been reduced by up to 96%. A number of freshwater fish species which are endemic to the south-west of Western Australia are found in the Canning River system, however studies of fish and fish habitats in the area have shown that fish numbers are low due to a loss of habitat and a loss of linkage between breeding areas due to low flows, preventing fish migrating upstream and reaching important breeding and nursery grounds. Stagnant water caused by a lack of water flow has provided a suitable habitat for successful breeding of an introduced pest, the Mosquitofish
Mosquitofish
The mosquitofish is a species of freshwater fish, also commonly, if ambiguously, known by its generic name, gambusia. It is sometimes called the western mosquitofish, to distinguish it from the eastern mosquitofish . It is a member of the family Poeciliidae of order Cyprinodontiformes...
.
Damming of the Canning caused dramatic flow reductions that significantly altered downstream aquatic macroinvertebrate communities. The lack of water flow has also resulted in a poor flushing effect below the dam wall. An excessive amount of nutrients from fertilizers and animal waste has caused algal blooms and eutrophication
Eutrophication
Eutrophication or more precisely hypertrophication, is the movement of a body of water′s trophic status in the direction of increasing plant biomass, by the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage, to an aquatic system...
.
Many river pools which are an important summer refuge and habitat for aquatic and terrestrial flora and fauna have been lost due to sedimentation
Sedimentation
Sedimentation is the tendency for particles in suspension to settle out of the fluid in which they are entrained, and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity, centrifugal acceleration...
and modification of the flow regime caused by impoundments in the Canning River.
Periodic flooding of the Canning River from the dam is required to disperse seed, stimulate germination and ensure seedlings survive, recharge shallow groundwater tables that are important during periods of drought and to discourage and prevent weed growth. However during times of low rainfall periodic flooding is reduced.
Recreation
A number of recreation activities occur in and around the dam and catchment area. Canning Dam features a number of picnic areas (with gas barbecueBarbecue
Barbecue or barbeque , used chiefly in the United States, Canada, the United Kingdom, New Zealand and Australia is a method and apparatus for cooking meat, poultry and occasionally fish with the heat and hot smoke of a fire, smoking wood, or hot coals of...
s), look outs and historic walks - many with disabled access. Bushwalking occurs throughout the catchment, particularly along the Bibbulmun Track
Bibbulmun Track
The Bibbulmun Track is a long distance walk trail in Western Australia. It runs from Kalamunda, east of Perth to Albany and is almost 1000 km long...
, which passes through the catchment about 10 km upstream of Canning Dam. Several mountain bike
Mountain bike
A mountain bike or mountain bicycle is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines,...
trails run either through the Canning National Park or adjacent State Forest areas.
The Canning Reservoir, Canning River and tributaries are illegally fished for marron
Marron
Marron is a name given to two closely related species of crayfish in Western Australia. Formerly considered a single species, it is now thought to comprise two species, the critically endangered Cherax tenuimanus, and the species which is outcompeting it, Cherax cainii.Marron make excellent eating,...
, especially during summer. Boating, fishing and swimming are prohibited in the reservoir for health and hygiene reasons. Unauthorised camping (including overnight stays and/or outside of designated areas) and unauthorised trail establishment occur more and more frequently in the Canning catchment. Unauthorised vehicle access, illegal fishing and pig hunting also occur. Such activities represent a significant risk to water quality.
See also
- Canning River
- Canning TunnelCanning TunnelThe Canning Tunnel was constructed between 1973 and 1975 to link Canning Dam to Perth's Integrated Water Supply System. It was built to replace the Canning Contour Channel which was a depression era public works project of the 1940s and constructed in conjunction with the opening of the dam.The...
- List of reservoirs and dams in Australia
- Swan RiverSwan River (Western Australia)The Swan River estuary flows through the city of Perth, in the south west of Western Australia. Its lower reaches are relatively wide and deep, with few constrictions, while the upper reaches are usually quite narrow and shallow....
- Serpentine Dam, Western Australia