The heavy rain drenching the South has caused flooding at Tuatapere's water treatment plant, which has stopped working.
Emergency Management Southland (EMS) advised of the news this evening.
EMS said there was eight hours' worth of drinking water available in the reservoir.
"Residents are advised to conserve water urgently. They can do this by not taking showers, washing dishes or flushing the toilet."
EMS said the treatment plant cannot be repaired until the water recedes.
Southland District Council is sending three water tankers to Tuatapere to provide drinking water until the plant can be repaired.
The news comes after a region-wide state of emergency was declared for Southland this evening.
