The high temperatures that hit the city earlier in the week have pushed up the demand for water and put the supply network under extreme pressure, says Christchurch City Council head of three waters and waste Helen Beaumont.
On Monday, she said more than 260 million litres of water was used in Christchurch - that's an average of 552 litres per person.
A similar amount was used on Sunday when the temperature in the city peaked at 35 deg C.
The measurements are the highest recorded for the city’s water use in a decade.
"Over the past few days we have struggled to get water through the pipes and into the reservoirs fast enough to meet demand," Ms Beaumont said.
"Our concern is that if the demand for water doesn’t lessen significantly, we won’t have adequate flow and pressure in some areas, which is also a big concern when it comes to the city’s preparedness for fighting fires.
“We don’t want to have to impose water restrictions, but if the demand doesn’t ease off, we will have no choice.
"We need people to stop using sprinklers and garden irrigation systems to water lawns and gardens.
"If your garden needs watering, use a hand-held hose and water before 7am or after 9pm, when it’s cooler. And please, avoid watering lawns or grass berms."
Ms Beaumont said the current peak demand in the evenings is putting extreme pressure on the network.
"We’re seeing huge spikes in water demand between 4pm and 9pm - mostly due to garden watering on top of the usual household water use when people get home from work - and it’s this peak flow that the network is struggling to cope with.
"Despite the cooler weather forecast, there isn’t going to be much rain in the coming days, so we need people to heed the ‘water like you oughta’ message and practise good watering habits now and when temperatures rise again.”
The council introduced level four water restrictions - the highest level of restrictions - in parts of Banks Peninsula on Monday after streams that supply drinking water to Akaroa, Duvauchelle and Takamatua dropped suddenly.
Level four restrictions means all use of water outside the house must cease. Hand-held hoses, unattended hoses, sprinklers and garden irrigation systems are not permitted at any time.
