'Get a bigger tank': Auckland's 'unprecedented' dry run to be more likely with climate change

An "unprecedented" dry run parching Auckland's rural residents is providing a glimpse into the future under the latest climate change models.

Auckland is into its longest-ever dry spell, with no more than a millimetre of rain falling in a day for over 40 days.

This, combined with more than 50,000 households on water tank supply, has led to massive water shortages with some residents facing two-month delays as the city's tankers are run off their feet.

Aucklanders on the town supply are also using record-breaking amounts, with the storage dams now down to 67 per cent of capacity, well below the historical average of 82 per cent, and showers forecast in the coming days are likely to have little effect.

Climate scientist Professor James Renwick warns this kind of summer will soon not be out of the ordinary.

In fact just seven years ago, during the summer of 2012/2013, Auckland experienced similarly-dry conditions, which researchers linked to climate change.

"That study showed a fairly weak link to climate change, but for the entire upper North Island we are talking droughts becoming twice as likely in the next 50 years, and increasing after that.

"Unless we see big changes in greenhouse gas emissions, it will continue to accelerate over the next few decades."

Watercare's future water network strategy. Image / Watercare

A Niwa report found if the planet continued to warm on its present trajectory, there could be at least 10 to 15 extra-hot days - over 25C - in Auckland each year by 2040.

This climbed to 60 to 70 by 2090, and 70 to 80 by 2110.

Renwick said by the end of the century the region was looking at about 10 per cent less rain on average annually.

But that did not mean a little less every month, rather more hot and dry spells followed by intense downpours.

The hotter temperatures would also increase evaporation, increasing the risk of drought.

"Water is absolutely going to be an issue for Auckland.

"There will be more intense dry spells, but because of the warmer air and increased moisture, when it rains it will be much more intense.

"So if you have the ability to capture that, then you will be more able to cope with the dry spells.

"This is cold comfort for those struggling now, but my advice would be - get a bigger tank."

According to Watercare, which manages the city's water network, the future is secured by storage dams, aquifers and the Waikato River to draw from.

Watercare recently launched a campaign encouraging Aucklanders to conserve water, which will help delay the need to increase supply.

But for those on tank supply the future is much less certain.

Auckland Council has been unable to provide exact figures but estimates there are about 50,000 households on rainwater tanks across the region with a large increase in recent years, particularly around the Rodney and Franklin wards.

Watercare's future water network strategy. Image / Watercare

Auckland Council's head of water strategy Andrew Chin said this summer's dry run was "unprecedented".

With these long, hot periods set to increase in the near future, Chin said once they'd helped residents struggling with water get through this summer the council would look to assist with increasing capacity to deal with the impacts of climate change.

Auckland Council declared a climate emergency last year, signalling the council's intention to put climate change at the centre of work programmes and decision making.

Its draft Climate Change Action Framework also noted a "key move" was to "find and deliver alternative water supply options to address climate change and population growth".

"We'd like to see people thinking about what kind of storage they have, potentially increase capacity if they can, and become more resilient," Chin said.

The council was also looking to "remove the red tape" to allow more residents - urban included - to install water tanks.

"Collecting stormwater will not only relieve pressure on the city network and delay the need to increase supply, but reduces the amount of runoff during storm events, improving our waterways."

While the council encouraged development near areas with good transport and infrastructure, Chin said there was nothing stopping people building in rural areas.

Still, with wastewater and reticulated supply connection costs as high as $20,000 to $30,000 in places, many residents had opted not to connect even where they had the option.

Watercare estimates there are several thousand properties about Whangaparaoa Peninsula, Snells Beach, Warkworth, Patumahoe, Clarks Beach, Glenbrook Beach, Wellsford, Helensville, Kumeu, Riverhead and Huapai that could connect to the reticulated supply but have chosen not to.

"If you have a pipe outside your house now is probably a good time to re-evaluate, as this is going to become more frequent," Chin said.

The council worked with Watercare and developers on areas of intensive development where the network could be extended to, including Clevedon where work had recently begun.

There the council had negotiated a voluntary rate for residents to pay off the connection fee over time.

Chin said this could be an option for other parts of the city if residents requested it.

To get through this summer Chin urged people to continue to keep an eye on their tanks, cancel orders if they are not needed, and work with their neighbours in sharing water where possible.

On Monday, Aucklanders used 561 million litres of water - equal to the record set on February 4.

A Watercare spokeswoman said while dam levels were falling it was normal for this time of year, before being replenished over winter.