1924 - Modifications and Enlargements
During the 1920's Melbourne's need for water seemed insatiable
and as the construction of Maroondah and O'Shannassy storages fell behind schedule, other options to rapidly augment supplies
to Melbourne were pursued.
In 1924 works commenced to increase the height
of the walls of the O'Shannassy aqueduct so it could carry a greater volume of water. The inverted siphons were
also duplicated to provide for the inceased flow.
By increasing the height of the channel walls by a relatively
small amount - top width was increased from 9 feet 3 inches to 12 feet 11 inches and depth increased from 3 feet 4 inches
to 5 feet 2 inches - the capacity of the aqueduct was effectively tripled from 90.7 megalitres (20 million gallons)
per day to 272 megalitres (60 million gallons) per day (although, in practical terms, the aqueduct ran "full" at 50 million
gallons per day).
The color difference and the join in the cement walls of the aqueduct are still clearly visible. A number of other aqueducts
serving Melbourne were also enlarged at the same time.