Rainy day has silver lining

The deluge of rain across the Auckland isthmus on Monday night brought misery on top of hardship to many residents of Kumeu, Huapai and the west coast. The flood waters have yet to recede fully and the cost of damage will be counted in the millions, on top of the losses felt during Covid-19 lockdowns.

But if there's a silver lining to be found under these dark clouds it's the knowledge that Auckland's water-woes are well and truly behind us after 18 months of near-drought and water conservation.

The cost for flooding in the north west of Auckland will be in the millions. Photo / Dean Purcell

The Waitakere Ranges received between 220 and 270mm of rain overnight Monday which saw flooding waist-high in Kumeu and surrounds: it also had the result of filling local dams to overflowing with all dams out west registering 100 per cent, the exception being the Lower Huia dam which is 94 per cent full.

The Waitakere dams are collectively holding 14.57 gigalitres, compared with just under 8.4 gigalitres in July, which is about the same as in July 2020 when we were being asked to take shorter showers and not wash the car.

The dams to the southeast of Auckland, in the Hunua ranges, have also fared pretty well recently, despite receiving less than half the western rain totals.

The Lower Nihotupu Dam is overflowing after Monday's heavy rain. Photo / Alex Burton

These reservoirs are the true giants of the Auckland water storage system with two dams, Cosseys and Upper Mangatawhiri, able to hold more than twice the capacity of all the Waitakere dams put together. The largest of them all, however, is the Mangatangi that can hold 35.3 gigalitres when full and is currently at 69 per cent - a few drops under 25 gigalitres.

The total current storage for all dams is at 73.2 per cent according to Watercare yesterday which put us some way ahead of a year ago at 66.75 per cent, but still behind the beginning of September 2019 at 78.1 per cent and a long way off the average of 89.2 per cent for this time of year.

Watercare is asking us all to be careful with this, still, precious resource and has a target of 410 million litres per day as a rolling average over seven days.

On Tuesday, Aucklanders used just 360 million litres and the seven-day rolling average is 364 million litres. The drop is probably reflecting the downturn in business activity due to the level 4 lockdown.

But the silver lining from that, surely, is that we're keeping a little more in the tank for a not-so rainy day.