 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 <unk> 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 . 
