Wannon Water service delivery general manager Ian Bail said the organisation had teams working extra hours to maintain services and protect the environment, but confirmed overflowing had occurred.

“The deluge means that sewerage systems receive much higher flows than normal, mainly due to stormwater getting into the pipes,” Mr Bail said.

“Stormwater is not meant to be connected to sewer pipes, but in cases like this, even groundwater can flood the sewer network. In places like Coleraine and Casterton we’ve also had floodwaters entering sewers directly.

“The unusually high flows in the sewer network mean that our sewer pump stations are trying to shift much greater volumes of water than normal, and in some cases just haven’t been able to keep up.

“There have been some spills to the environment, but these have been mostly stormwater which has filled the sewers. Manholes and other access points into the sewer can also overflow when such heavy rainfall occurs.”

Mr Bail said some of the winter storage facilities for treated water had been completely filled, meaning water had been released into waterways in Mortlake, Casterton, Port Campbell, Terang, Cobden and Hamilton.

He said the releases had been monitored by the Victorian Environment Protection Authority to protect the local environment.

A severe weather warning was issued warning that heavy rainfall from between 20mm to 40mm could affect parts of the south-west on Tuesday night, and the SES warned up to 40mm could fall in the Hopkins River catchment area.

Bureau of Meteorology data shows 115.6mm of rain has fallen in Warrnambool since the beginning of the month, surpassing the monthly average.