Watercare calls for more water usage cuts despite heavy rain

Aucklanders are being asked to continue conserving water despite the region experiencing another night of torrential rain.

A record 239mm of rain fell overnight in some parts of the city but the downpour hasn't helped with city-wide water restrictions caused by the Tasman Tempest earlier in the month.

"It is a little bit shocking to be honest. The amount of water that's fallen is like nothing we've seen before," says Watercare's Water Supply Manager Priyan Perera.

Perera says the Ardmore Water Treatment Plant, which supplies up to two thirds of Auckland fresh water, is only operating at 70 per cent of its capacity due to unprecedented levels of silt in the water coming from the Hunua reservoirs.

"Ardmore typically expects a certain amount of silt but nothing like what we're seeing. Clarity levels are 100 times worse than we've ever seen. We're pushing the treatment plant beyond what it was ever designed to do," says Perera.

The reduction in water treatment capacity at Ardmore has resulted in Watercare asking people to reduce their water consumption by 20 litres a day - which, on the whole, they are doing.

A 400 million litres per day limit set by Watercare for the entire Auckland region has been exceeded on 11 of the 21 days since the Tasman Tempest hit at the beginning of the month.

But with large amount of silt still suspended in the Hunua dams and the torrential rainfall that continues to hit the region, Perera says the limit will stay in place for at least three more weeks.

"We are worried about further rainfall as the ground has opened up with slips and that means more sediment could be washed into the lakes. It's fairly nerve-wracking. Ardmore is the backbone of Auckland water supply and that's why we are asking Aucklanders to continue reducing their water consumption."