An estimated 30,000 megalitres of water has been lost after a dam collapsed at Cubbie Station. 

A dam wall has collapsed on QLD’s Cubbie Station, one of Australia's largest cotton-growing properties, flooding the surrounding country.

Locals are concerned that the event could coincide with a breached flow in the local river system, which is currently in major flood.

Cubbie Station's proximity to the watercourses and rivers branching from the Balonne means the farm often experiences small flood events, as well as a one-in-10-year major flood inundation.

The owner of Cubbie Station, Macquarie Asset Management Fund, has declined to comment.

Cotton Australia has also declined to comment.