The Barwon River at Mungindi is expected to peak at the major flood level in the coming days, and a boil water alert is still in place.

The State Emergency Service (SES) and other agencies have been sending in helicopters twice-a-day to stock up supplies for the isolated town.

The latest SES flood bulletin on Monday afternoon said the Barwon River could peak at 7.4m on Wednesday, and was already at 6.7m.

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The Carnarvon Highway has been closed to all traffic between Mungindi and Moree, which experienced a major flood two weeks ago.

SES spokesman David Rankine said it was "frustrating" and "ludicrous" to receive a number of reports about tourists and truckies ignoring the road closed signs.

"The Carnarvon Highway has been underwater for some time now and the road is severely damaged ... it will be underwater for a fair while yet," he said.

Mr Rankine said people who take the risk are putting themselves at danger and further damaging the fragile road.

He said police had increased patrols at both ends of the highway to remind people it is illegal to drive along a closed road.

A visiting team of SES volunteers from Sutherland, Sydney, spent the Easter weekend getting their hands dirty in Mungindi to help out.

Mr Rankine said crews were choppered in to help local emergency service workers give out bottled water, deliver essential supplies and stock up sandbags.

"Flood teams are moving from the coast and the metropolitan areas out west to give us a hand ... with Easter and the school holidays, we welcome it with open arms," he said.

Mungindi itself is not expected to be inundated with floodwater, but the roads and outlying properties could be affected for some time.

Mr Rankine said helicopter drops would continue for as long as they were needed.

The SES has been holding meetings with communities downstream of Mungindi - heading toward the Walgett area - in anticipation of floodwaters arriving there in the coming weeks.

Flood updates are available on the SES and Bureau of Meteorology websites.

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