The 23 year old was flown to hospital by NRMA CareFlight helicopter after tumbling down a ravine beside the Sydney water supply channel at Horsley Park in Sydney’s west.

Ambulance officers called the CareFlight medical team to the rescue at 9.30am.

The NRMA CareFlight doctor said the man had slipped on metal sheeting and wet grass before tumbling down a 35 metre embankment.

The man’s right ankle became wedged on a protective grating beside the water supply channel.

Had he tumbled into the channel, with his leg caught, he probably would have drowned, a CareFlight spokesperson said.

The man’s location presented a difficult rescue for ambulance, police and the helicopter team.

Nearby high tension wires made it unsafe for the CareFlight choppper to winch him out.

Instead, once his leg was freed, he was placed in a rescue stretcher and carried 500 metres along the drain to where he could be placed on board the helicopter.

The man was flown to Liverpool Hospital for treatment to his fractured ankle and was in a stable condition on arrival shortly after 11am.