Murray-Darling Basin Authority acting chief executive Andrew Reynolds said 27 millimetres of rain fell over the dam in a short period on Tuesday.

With the dam at 99 per cent capacity, effectively full, this reduced airspace to 20Gl, prompting operators to increase releases to create airspace.

"We anticipate flows downstream of Hume Dam will remain within the river channel however if rain and run-off are higher than expected, we may need to increase the release of water in the days ahead," Mr Reynolds said.

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"The situation is quite dynamic, and our river operators are working round the clock and in close consultation with the Bureau of Meteorology and WaterNSW to manage releases from Hume Dam."

Mr Reynolds said the release methods also considered water quality, with, with blue-green algae currently affecting the dam and low dissolved oxygen levels present immediately downstream.

"To help manage low dissolved oxygen, we are releasing some water through the valves," he said.

"This creates a spray which entrains oxygen into the water as it enters the river."

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