It has committed to upgrading its assets, including investing $1.9 billion on securing water supplies and building new water infrastructure.
The unprecedented rainfall on March 7-8, dubbed the Tasman Tempest, delivered more rain in a few hours than typically falls in the entire month of March.
Landslips and silt washed down from the Hunua Ranges clogged the water filters at the Ardmore plant, which meant it struggled with treatment. Ardmore provides two-thirds of Auckland's water.
According to Niwa's High Intensity Rainfall System, the 225mm that fell in 12 hours on March 7 in Upper Hunua exceeded a one-in-100 year event.
Auckland, according to readings taken at Mangere, tied its wettest March hour on record with 27.6 mm between 5pm and 6pm on March 10 since hourly records began in 1965.