Storages have increased modestly across the river system after welcome deluges soaked large parts of Queensland and NSW.

The Murray-Darling Basin Authority's Andrew Reynolds said some rivers were seeing significant flows for the first time in years.

But the executive director of river management said more rain was needed to break the prolonged dry spell.

"It's the story of the haves, and the have-nots," Mr Reynolds said on Wednesday.

"We've had heavy falls and associated flooding in several northern catchments but generally it's been uneven and some areas have seen little or no rain at all."

Water quality is a concern across the basin, with fish deaths in the Moonie, Culgoa and Balonne rivers in Queensland.

Mr Reynolds said more were likely to die as flows move downstream.

"The legacy of the bushfires is also with us and there is still a risk that more ash and sediment will enter waterways," he said.

Northern storages are up four per cent to 11 per cent, while southern storages are steady at 33 per cent.

Between February 16 and Sunday, 210mm was recorded in Barradeen between the southwest Queensland towns of Charleville and Augathella.

To the west at Mitchell on the Maranoa River, a little less than 160mm fell in the same seven-day period.

Storages in some regions are likely to rise, but many remain close to empty with rain falling downstream.

Mr Reynolds said flows across the basin continued to be below average.

"Not only has the rain been extremely variable, the drought has left the soil bone dry," he said.

"Much of the rain is soaking into the ground before it reaches the waterways and the storages."

Australian Associated Press