The operator of the Yallourn power station says extra water flooding the open-cut mine will not affect energy generation.
The Morwell River diversion collapsed in June last year, flooding the mine.
Since then, the Environment Protection Authority (EPA) gave Energy Australia emergency discharge approval to pump 150 million litres of water out of the mine and into the Latrobe River each day.
Recent heavy rain is proving too much for the system to handle and extra water is now flowing into the mine.
Energy Australia says the company will not need to go back to the EPA to ask for permission to release bigger volumes of water.
A spokeswoman says the flooding may create problems with coal transportation but energy generation at Yallourn power station will not be affected because coal can be sourced from elsewhere in the mine.
© ABC 2013
22:36 EDT The damage bill from a supercell storm that hit south-east Queensland yesterday afternoon with cyclonic winds and softball-sized hail could reach $150 million, Queensland Premier Campbell Newman says.