Up to 80mm over four days has been predicted in some areas, leading to fears that mass erosion will affect water supplies.

Tamworth Regional Council has reached out to the NSW Soil Conservation Service for advice and other councils have done the same.

University of NSW water expert Stuart Khan said fire-affected catchments, such as Dungowan and parts of Chaffey, would be particularly unstable.

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"The soil is kept together by tree roots and other biomass - if enough of that has been burnt away, the catchment will be prone to erosion and even mudslides," Dr Khan said.

"If it rains heavily and too much soil and mud washes in to the reservoir, the sediment can overwhelm the treatment process."

Tamworth Regional Council's water director Bruce Logan said the state government had made some funding and resources available to help reduce runoff, but wasn't sure if they would be installed before the rain hit.

"[We're looking at] the installation of silt curtains, to catch silt as much as we can," Mr Logan said.

"In general, after any significant inflow, whether it's in a good period or in drought, the quality of water in the storage falls significantly for a few days after it happens.

"We expect that will happen this time. We think it will fall to a higher level than what we are used to and maybe for a longer period."

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Despite the concerns, Mr Logan said for now, there was no indication the council wouldn't be able to treat the water.

"We do have the 110-megalitres storage behind Calala, which we can tap into if we can't treat the water [out of the Peel River]," he said.

Dr Khan said Tamworth wasn't the only region scrambling to prepare for the potential sediment overload.

"It's something they're worried about up and down the state," he said.

"Everyone is dealing with it and because of that, resources and experts are quite thinly spread and hard to get.

"Everyone is suddenly wondering what's going to happen when we get this big rainfall event. We're in it together and hopefully it won't be as severe as some of the predictions have been."

Tamworth Regional Council has also reached out to the state government's water experts to get advice about the best way to treat water that's been contaminated by ash.

"We aren't very experienced in treating water that is heavily contaminated with ash," Mr Logan said.

"We're trying to get some advice about what that might mean for us so we're ready if that happens."

Despite the uncertainty, Mr Logan said the water wouldn't be released in to reticulation if there was a health risk.

Chaffey Dam currently sits at 13.1 per cent capacity.