Farmers and other irrigators in Otago are being asked to start conserving water as warm, dry weather reduces flows in the region's rivers.
Otago Regional Council says irrigators should prepare for potential water rationing, with dry weather predicted for the summer.
It says the Kakanui, Shag, Taieri, Manuherikia and Pomahaka rivers are already at low levels not normally seen until late in the season.
The council says if there's no substantial rain soon, rationing could begin as early as this month.
It says farmers should manage their irrigation as efficiently as possible.