Several hundred metres of Sydney’s Metro remain under water, with drainage pumps in the underground tunnels unable to cope with the torrent of rainfall dumped on the city.

A new image understood to be of the inundated network reveals millions of litres of brown storm water sitting at platform height.

A photograph understood to be Sydney's flooded Metro network.

The flooding occurred in the decade-old tunnel between North Ryde and Chatswood, which was retro-fitted during construction of the new, multi-billion dollar Metro.

While the 15 kilometres of new Metro tunnelling features waterproof gaskets that prevent flooding, the old tunnel relies on pumps to get rid of water that seeps into the network.