The Minister for Primary Industries, Nathan Guy, is expected to declare South Canterbury and North Otago drought areas when he visits the rapidly depleting Opuha Dam, near Fairlie, today.
Parts of Canterbury, Marlborough and North Otago are suffering from abnormally dry conditions and most of the country is drier than usual.
Tony McCormick, chief executive of Opuha Water, said the dam, which has been on restrictions since December, was now just 9.5 per cent full.
"We are looking very much at a scenario of nearly zero storage," McCormick said.
Irrigation will stop when there is a metre of storage left, which will be then used to augment the nearby Opihi River.