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.