The Thomson Dam Spillway in the process of overflowing for the first time in 26 years.
The Thomson Dam experienced its first overflow in 26 years on the weekend as recent rains caused it to reach full capacity.
The dam, north of Walhalla, holds more than half of Melbourne's water supply. It has not spilled since 1996.
Melbourne Water confirmed the dam began to spill on the weekend.
"Given recent high rainfall in the Thomson catchment, Melbourne Water has been carefully managing storage levels through controlled releases from the Thomson Reservoir to the Thomson River down to the Gippsland Lakes, to maintain a safe operating range of our storages.
"Melbourne Water aims to have storages as full as possible before the start of future dry conditions and droughts to avoid the impacts water restrictions can have on the community."
