Christchurch City Council may consider charging residents for excess water use unless conservation measures are brought in.
A draft water supply strategy has been released for public consultation.
The document says householders use almost two-thirds of the city's water supply, and one option may be to charge residents for excess use.
Council spokesperson Jenny Ridgen said demand for water could outstrip supply in the next few decades as the city continues to grow.
But she said the problem would be reduced if people change their behaviour.
Ms Ridgen said residents can have their say on water conservation by filling out a questionnaire on the council's website.