The Dunedin City Council is asking Waikouaiti, Hawksbury and Karitane residents to cut down on water use while levels in the Waikouaiti River are low.
The river has dipped below a level of 350 litres per second, which means the council must implement water conservation measures.
Council group manager 3 waters David Ward said voluntary restrictions were in place which it asked people to observe.
"Unless we get some further rain or we can all sufficiently reduce our water use, we may need to take further action to maintain flows in the river."
Visit dunedin.govt.nz/services/water-supply/saving-water-tips for water conservation advice.
