 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 <unk> and is an <unk> 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 <unk> . Currently the dam supplies approximately 20 percent of Perth 's fresh water . <unk> into the Canning Reservoir is estimated to be 22 gigalitres ( 780 @,@ 000 @,@ 000 cu ft ) and has a storage capacity of 90 @,@ 352 <unk> ( 3 @,@ 190 @.@ 8 × 10 ^ 6 cu ft ) . 
