Some businesses and farmers in Central Hawke's Bay may start rationing water as parts of the Waipawa and Tukituki rivers are already bone dry.
It comes as figures obtained by RNZ show the top six water consent holders in the district are using more than half of all allocated water from the Ruataniwha Aquifer and rivers.
Surface water user group chair Alastair Haliburton said around 40 consent holders were considering rationing and rostering their water supplies this summer because of concerns that river levels were so low.
His own company, Medallion Pet Foods, which employed 14 people in Waipukurau, could go bust if it does not get enough water.
"If we don't get water we can't manufacture and the doors close," Mr Haliburton said.
Other businesses would be affected by the rationing, he said.
"It means that some crops probably won't be planted, or yields will be lower, livestock productivity is going to be lower ... essentially it means a scaling back of commercial activity."
Ongaonga farmer Alistair Setter was also worried about getting enough water for his crops this summer.
A section of the Waipawa River near his home dried up in mid-October.
"On a dry year it might dry up around Christmas time but it's never done this before," he said.
He worried the big water users were taking too much water from the aquifer, which affected the flow of the Waipawa and Tukituki Rivers.
Scientific evidence showed the water levels in the aquifer had been dropping for several years and some residents in Ongaonga and Tikokino have had to drill deeper bores or install pumps to fill their taps.
Mr Setter feared what might happen if Hawke's Bay Regional Council allowed a further six big water users to take another 15 million cubic metres of water from the aquifer.
It was a concern shared by councillor Tom Belford.
He asked the council to look at who was using the water and when they crunched the figures for the first time it showed that the top six consent holders were all dairy farms and they were taking more than half of all the allocated water in Central Hawke's Bay.
The largest, Bel Group Dairy Farms, took two and a half times the amount used by the townships of Waipawa and Waipukurau put together.
"You have this enormous amount of water being used by very few people. I think that raises some equity issues.
"It's been going on for a while but it's only now that some landowners who can't get drinking water have pounded on our doors that we've actually dug into the detail that we should have done before."
Regional council chair Rex Graham said he did not know how the council got itself into that situation.
"We are looking at the numbers now but it is a concern that we have so much water in the hands of so few."
He said no one wanted businesses going bust because they could not get enough water and options were being explored to help those who needed it.
A public meeting on water supply was being held in Waipawa on Tuesday, 27 November.