Of particular concern is the potential for dust containing iron oxides and phosphates to trigger algal blooms in coming weeks and months.

Unless heavy rains quickly flush the catchment areas, it is feared much of the dust will settle in waterways such as Lake Macquarie, the Hunter River and the Myall Lakes.

With the catalyst of warmer weather, the nutrient load could trigger widespread algal blooms over summer.

A Department of Environment and Climate Change spokeswoman said staff would be sampling lakes and using satellite imagery to monitor ocean water for additional algal growth.

"It should be noted that in spring and summer there is a natural up-welling of nutrient-rich cold water from deep in the ocean as part of annual ocean currents, which results in algal blooms off the NSW east coast every year," she said.

Hunter Wetlands, Shortland, chief-executive Ken Conway said a nutrient reading for the wetlands was due next week.

"One would anticipate that the nutrient levels will go up," he said.

"If we have good rain shortly it will potentially flush the problem out to sea. If we don't, depending on where the dust settled and depending on what nutrient load was in the dust, it could certainly lead to enhanced algal blooms during the summer months."

Recently retired Lake Macquarie and catchment co-ordinator Jeff Jansson said time would tell what impact the dust would have on the lake's nutrient levels.

"I suspect it will probably have a similar impact as a large storm," he said.

"In two or three months time you might start to see some change in the key water quality indicators."