Despite record rainfall and widespread flooding in northern Queensland, none of the water will make its way into the Murray-Darling Basin to replenish starved waterways, the system's authority has said.

Parts of Townsville have been evacuated after a year's worth of rain fell in nine days, as further south truckloads of dead fish attributed to water mismanagement and drought in New South Wales are rotting on the banks of the Darling River.

Loading

The MDB Authority (MDBA) said the slow-moving monsoon trough over Queensland was not forecast to head south enough to help.

"If the system moves a significant way south in the coming days to rain in the upper catchments of the basin, it is not guaranteed that flows would reach as far south as Menindee Lakes," a MDBA spokesperson said.

"That's because the river system is currently so dry that much of the water would soak into the river beds and be lost through evaporation.

"It will take significant rains to boost flows throughout the system.

"Depending on the direction the current weather system moves, it is possible it may end up replenishing the catchment of the Lake Eyre Basin instead."

The Bureau of Meteorology has forecast the heaviest rainfall over central and north Queensland to head progressively north-east to the coast in the coming days.

A spokesperson said the bureau was unwilling to make "guestimates" of overall rainfalls and water flow at this stage during the monsoon or how it might flow downstream.

Some of the water is falling in the upper reaches of the MDB, but the BOM considers Lake Eyre Basin to receive more benefit where more than 100 millimetres have fallen.

"Only a trickle is likely to reach SA two to three weeks from now," BOM stated in a tweet on Tuesday.

Lake Eyre last received floodwaters from north Queensland in mid-2018.