The Department of Water, Land and Biodiversity Conservation’s chief executive, Rob Freeman, said boat access past the Murray Mouth has been excluded each winter since the sand pumping project began in 2002.

"Boats have been able to travel past the Murray Mouth since the October long weekend last year," he said.

"While dredging work is concentrating on an area just inside the Mouth, by the end of April, it will move to the Hindmarsh Island side of the Goolwa and Coorong channels to remove sand that has built up over summer.

"This will mean that as of April 28, boats will not be able to travel past the Mouth until further notice."

A line of yellow buoys will cross the channels either side of the Mouth to establish a total exclusion zone for all vessels.

While access to the Murray Mouth over the 2007/08 summer had been popular with boat operators, the exclusion zone will occur at a time when the number of recreational boats begins to diminish.

Mr Freeman said there were alternative locations where boats could still be launched.

"Boat operators can access the Coorong using the boat ramp at Mundoo Channel, and the Goolwa Channel between the Goolwa Barrage and the Mouth, by launching at Beacon 19," he said.

"The continued low water levels in Lake Alexandrina mean that there will be no access through the locks at Tauwitchere or Goolwa, because of these low water levels, boat operators should use extra caution in this area."

The only exception to the boat exclusion will be unladen commercial vessels, providing a safe passage can be negotiated and suitable notification is given.

For further information phone 8204 8605.