Downpours in west Auckland see spike in dam levels

The highest catchments feeding into Waitākere, Upper Nihotupu and Upper Huia (pictured above) dams have all recorded more than 200mm of rain in just 12 hours.

The deluge of rain in west Auckland over the past 24 hours is rapidly filling up Auckland’s Waitākere dams and has boosted the city’s total dam storage by more than 7 per cent.

The highest catchments feeding into Waitākere, Upper Nihotupu and Upper Huia dams have all recorded more than 200mm of rain in just 12 hours.

Auckland Mayor Phil Goff says: “The heavy rain over the past 24 hours which has caused flooding in the north and west of the region has also had a significant impact on Auckland’s dam storage levels.

“Total dam storage was at 72.1 per cent at 10am this morning, up from just 64.9% before the downpours began—an increase of more than 7 percentage points.

“Auckland Emergency Management and emergency services are working to support those affected by flooding and we ask everyone to stay safe and call 111 if they are in immediate danger.

“The flooding is also affecting Watercare’s ability to deal with wastewater overflows. These can be reported to Watercare as normal and will be addressed as soon as it is safe to do so.”

Watercare chief executive Jon Lamonte says: “We’ve had more than a month’s rain in 12 hours in our higher Waitākere catchments.”

The rain means Waitākere, Upper Huia and Upper Nihotupu dams are now spilling, and the lower dams are filling up quickly.

“Upper Huia Dam was just 45 per cent full at 9pm last night, and by 6am it was spilling,” Lamonte says. “Our western dams are much smaller than our Hūnua dams, and therefore they fill up much more quickly in heavy rain.”

The Hūnua catchments received between 30mm and 50mm overnight.

“While this rain is certainly helpful in terms of our water storage, we are still recovering from drought and we need to continue to be mindful of our water use. Aucklanders have done an outstanding job over the past year and we’ll need to keep up the great work with these water savings, especially when the days start getting longer and warmer.”

The deluge has caused varying water quality at Waitākere Dam, and as a result, the Waitākere Water Treatment Plant will be shut down for at least the next 24 hours.

The rain also means Auckland’s wastewater network has been inundated with stormwater, which is causing wastewater overflows in west Auckland.

“Our crews can’t deal with these overflows until the flooding has subsided, but please do report any overflows on our website – we will clean these up as soon as it is safe to do so,” Lamonte says.

“This may take longer than normal, particularly with more rain expected and our backlog growing.”

Mayor Phil Goff says the floods have increased the pressure on Aucklanders affected by lockdown.

“Flooded homes and properties have added further trauma to the lives of people already under an Alert Level 4 Covid-19 lockdown,” Goff says.

“Emergency services have been out from the early hours this morning providing assistance to those who have had to evacuate their homes. I want to particularly thank the surf lifesavers who assisted in the rescue of some people.

“Rain levels in some parts of west Auckland have been unprecedented, with Kumeu receiving around 200mm of rain—much more in one day than would normally occur over the entire month of August. Further rain is still anticipated before this afternoon but hopefully not at the same level of intensity.

“Most families whose homes have been flooded have evacuated to stay with family and friends but Auckland Council has opened up a shelter at 6 Henderson Valley Road, and the Kumeu Rugby Club has made the clubrooms at 2 Alexandra Street available for locals seeking shelter.

“Some families will not be able to return home until repairs are carried out and assistance will be available through council for families needing hotel or motel accommodation.

“Some roads, including SH16, may be closed for some time and people are urged not to try to drive through flooded roadways.

“Every effort will be made by emergency services to provide assistance where needed and work will take place to restore access and power where these have been lost because of the severe weather conditions.

“The one upside—a silver lining to the dark clouds—is that Hunua lake levels have risen from 64 per cent to 72 per cent full and west Auckland storage dams are overflowing.”