Otago Regional Council is warning it will take action if it finds evidence of landowners irrigating illegally.
While some regions are having a wetter than normal summer, Otago, like Northland, has been unusually dry.
The council's environmental services manager Martin King says a lack of rain over the past month has increased the number of rivers and streams which are below their minimum flow level for irrigation to be allowed.
Mr King says up to half of the 3500 landowners who have irrigation consents in place could be affected in some way by water restrictions.
He says sheep and beef farmers, market gardeners, orchardists and dairy farmers are all affected by the irrigation bans.