Researchers from Griffith University have used sediment analysis to reconstruct weather patterns from 1500 years ago.
Using sediment from the mouth of the Brisbane River in Moreton Bay, the researchers were able to show that rainfall was highly variable across the period.
Large periods of drought were followed by prolonged periods of being wetter than average, challenging water planning that had relied on the last two hundred years of data.
The researchers have also discovered in recent floods, more sediment had been displaced into the river system, which is threatening water quality.