Canning Dam

Canning Dam
The dam wall and spillway
Location	Roleystone, Western Australia
Coordinates	32°9′9″S 116°7′42″E / 32.15250°S 116.12833°E / -32.15250; 116.12833Coordinates: 32°9′9″S 116°7′42″E / 32.15250°S 116.12833°E / -32.15250; 116.12833
Construction began	1933
Opening date	1940
Construction cost	£1.1 million (AU£, in 1940)
Operator(s)	Water Corporation
Dam and spillways
Impounds	Canning River
Height	66 metres (217 ft)
Length	466 metres (1,529 ft)
Reservoir
Total capacity	90,352 megalitres (73,250 acre·ft)
Catchment area	804 square kilometres (310 sq mi)
Surface area	501 hectares (1.93 sq mi)

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 gigalitres (780,000,000 cu ft) and has a storage capacity of 90,352 megalitres (3,190.8×10^⁶ cu ft).

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.

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 Depression 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.