Auckland water consumption on-par with post-flood target

updated By Talisa Kupenga

Auckland City Council met this morning to discuss the impact recent weather has had on the region. The city has been hammered by three major weather events in the past week that caused severe flooding and damage in localised areas.

Auckland's water consumption is on-par with post-flood targets, but the 20-litre cut-back per person per day will remain for the coming weeks.

Watercare Chief Executive Raveen Jaduram says "The target is 400 [megalitres] and in the meantime, we will keep increasing the capacity from Ardmore, but that's a struggle because we don't know how long it will take for the sediment to settle ... and at the same time we know that if customers demand is not going to be shooting up to the 460 [megalitres], which it was before the rainstorm, we'll be able to fill [the reservoirs]."

Ardmore Water Treatment Plant provides two-thirds of Auckland's water supply. Jaduram says the weather brought silt levels 100 times higher than normal, beyond the plant's processing capacity.

"Because the plant is normally automated, the level of sediment in the water when it came in, the plant decided to shut down. It said 'I can’t treat this'. So we've had to manually intervene and so we are now running the plant, I would say, in intensive care mode."

Jaduram says the usual sediment Ardmore treats eventually settles and separates from the water, but the sediment currently being processed does not, which means more cleaning and more delays.

"What we've got right now is called 'colloidal suspension' whereby it's sort of integral to the water and if left, it remains that way. So the way that silt is removed from water supply is we add Alum and then we flocculate and the Alum - and there's chemistry behind that - attaches to the sediment and they settle."

Auckland City Council says localised damage out West is still being assessed.