Federated Farmers says the Canterbury Regional Council's refusal to allow some farmers to exceed their groundwater limits this year will have a widespread impact on farming there, as the drought bites deeper.
Some farmers with seasonal restrictions on their ground water allocation have asked the council if they can increase the amount of water they can take, because they say they'll need more to get them through the irrigation season.
Environment Canterbury turned them down because it said limits were set for each zone for environmental reasons.
It said groundwater levels were now very low, particularly in the southern half of the region, where some wells have dropped to record levels.
Federated Farmers water spokesperson Ian Mackenzie, who is a mid-Canterbury farmer, said the main impact will be on dairy farmers, who have a longer irrigating season than cropping farmers.
"It includes everybody who has either changed the conditions of their consents in the past eight or nine years, or had new consents allocated.
"So it will have widespread but sort of random effects, because not everyone is on a seasonal allocation yet.
"It will mainly apply to pastoral farmers - dairy farmers - who have a longer season than arable farmers, so that with the very long, dry growing season that we've had this year, it doesn't matter how efficient you've been with your water use.
"If you're a pastoral farmer and irrigating 100 percent of your farm, you will either have run out of your season allocation or be about to run out."
Environment Canterbury said groundwater consent conditions were designed to provide reliable water supply for nine years out of 10 and this may be the one season in 10 when farmers have to manage with less water.
But Mr Mackenzie said there was a way around that that would be less disruptive for farmers.
"And that is, we allow farmers to take unused water forward, from one year to the next, or a proportion of their unused water, then in fact you could provide that 100 percent reliability if you're an efficient user of water in the wetter seasons, to enable you to get through in the drier seasons.
"We argued this when the Regional Council imposed these seasonal allocations eight years ago.
"At that stage, I don't think the Regional Council understood the implications on the economy and social fabric of the Canterbury region, of closing down irrigated farmers still in the middle of summer."