Wellington, Sept 6 NZPA - Some Canterbury farmland has risen by up to three metres amid reports of significant land scarring following Saturday's earthquake, Federated Farmers says.

The organisation was collating reports of farm damage to its 0800 327646 number.

Aside from homes and buildings, there was significant damage to pastures, fences, races and tracks, and ground water infrastructure. There were also concerns about unseen damage to grain silos.

"One call from a member, whose run off-block is on the fault line, explained there was scarring up to 100 metres wide running through their property. The land has been pushed up three metres in some spots. Of concern are very large ground cracks in other parts rendering it basically unsafe for grazing."

Meanwhile, heavy rain was today causing levels in the major Canterbury rivers to rise and people were being urged to steer clear of the stopbanks of the Waimakariri River below State Highway 1.

Agriculture Minister David Carter visited farms west of Christchurch yesterday and said between 100 and 150 had suffered severe damage.

"In true Kiwi spirit many of these farmers are not only dealing with damage to their own properties, but they're also helping out their neighbours," he said.

"Dairy farms are sharing generators to get cows milked and I heard of one shed designed for 400 cows milking 2000 over a 24-hour period.

"It is really heartening to see rural communities pulling together to help each other through such a tough time."

Mr Carter said many farms remained without electricity and that situation may last for several days.

Rural support trusts were working to provide assistance, particularly in restoring stock water systems, he said.

A mayoral relief fund and other appeals set in the wake of the disaster have already attracted millions of dollars in donations, including some seven-figure ones.

Christchurch remains under a state of emergency and aftershocks continue to present dangers to unsound buildings. The overall cost of damage is not yet clear but is expected to climb above $2 billion.