The 1862 gold fields water supply scheme: Victoria, Australia

A major water supply scheme to support mining at two significant alluvial gold fields in the colony of Victoria, Australia was undertaken in the 1860s. It involved a large clay core embankment dam on the Coliban river and aqueducts to serve the mining communities at Castlemaine and Sandhurst. In a new colony lacking hydrological records, estimation of the river flow and the flood characteristics presented a challenge to the designer Joseph Brady. The paper examines Brady's approach to estimating these hydrological parameters and the reaction of other engineers in the colony to the design. The scheme was modified during construction to increase the volume to be delivered, but the higher level of supply could not be realised. Also the climatic conditions in the colony produced occasional floods with a higher crest than Brady's estimate. Additional spillway capacity was provided during construction, but the peak volumes were such that the dam had to be held below full capacity level to prevent destruction through overtopping. Problems with the scheme brought about a programme of hydrological surveys of river catchments in the colony. Examination of 50 years of Coliban records shows the acumen of the original design engineer Joseph Brady.