Auckland's water storage sits comfortably above first stage of restrictions but dry periods loom

The Waitakere Reservoir which is well under capacity for this time of year. Photo / Dean Purcell

Auckland needs a phenomenal amount of rain next month if it has any chance of making up for the shortfall of this year's current total.

Around 180mm of rain normally falls in the Waitākere and Hūnua ranges over Auckland but an additional 265 to 370mm would be needed to break even.

On July 2, Watercare urged residents to be mindful of their water use over winter as the levels of water storage dams dipped.

For the first six months of the year, 424mm of rain fell in the Waitākere Ranges and 513mm in the Hūnua Ranges.

Normal rainfall over the same period would look like 796mm in the Waitākeres and 779mm in the Hūnuas.

Meanwhile, Niwa reports the Auckland region was looking dry before July but the several dumpings of rainfall provided some respite.

"Through the first 21 days, we're sitting at about 120 to 150 per cent of normal rainfall for the Auckland region, broadly speaking," meteorologist Ben Noll said.

"Auckland will have some chances for rainfall later this week but overall it might hedge slightly on the dryer side for the next two weeks.

"[But] July to September has a chance to be a bit wetter than the last three-month period going back to autumn and summer."

There has been significantly less rainfall in the Waitākere ranges, pictured. Photo / Dean Purcell

Federated Farmers Auckland provisional president Alan Cole said the past few weeks had helped grass growth.

"We're actually [showing] the first signs of spring, we had poor autumn growth ... it wasn't looking good for a lot of people but everything has corrected itself well," he said.

"Water coming up out of the ground starting to show now which is a benefit hopefully for Watercare because it means the ground isn't going to be soaking anymore and more will run off when it rains."

Between now and September, Niwa forecasts rainfall to be near or below normal for the north of the North Island and north and east of the South Island. Elsewhere, regions should be near normal.

Watercare's head of water Roseline Klein said while water levels had started to settle since the public plea was made, it is unlikely the shortfall will be recovered.

However, with the water level sitting at 65.9 per cent as of Monday morning, there is still plenty of wiggle room before restrictions are put in place.

The Mangatangi Dam in 2008 compared to June 30, 2019. Photo / Watercare

"The trigger point for voluntary savings is around 47 per cent and the trigger point for the first stage of restrictions is around 42 per cent," she said.

"Our focus is on managing factors within our control and on being proactive with factors beyond our control.

"We are being proactive by maximising production at our Waikato River and Onehunga aquifer treatment plants in order to reduce demand on our water storage dams."

Noll said an El Niño sitting over the central equatorial Pacific was partly to blame for the dry conditions so far this year.

"Known as El Niño Modoki, it's a non-traditional type of El Nino, in fact, we had one of these events unfolding in the early 1990s," he said.

"Folks might remember the Auckland water crisis in 1993-94 and the conditions that we're observing here in 2019 have some similarities."

El Niño disrupts normal weather patterns and can lead to intense storms in some places with droughts taking place in others.

And while it is tipped to continue for the upcoming months, Noll said there was a chance it could weaken and become less influential.

Klein said since Aucklanders were asked to use water wisely, Watercare had recognised a drop in demand "which is wonderful".

Examples of first-stage restrictions

• Washing vehicles using a bucket rather than an open hose;

• Reducing shower times to less than five minutes;

• And repairing leaking taps, pipes and toilets.