The head of Watercare has defended the organisation's drought response and says if Aucklanders want a more resilient system, they need to be prepared to pay.
The comments come as Auckland's dam levels continue to fall, with predictions they may only reach 70 per cent capacity come spring - meaning the region could see water restrictions last right through next summer.
Restrictions began on Saturday for the first time since 1994, amid the driest start to the year on record with only about a third of the average rainfall dropping to replenish rapidly depleting storage dams.
But they don't appear to be soaking in yet with Aucklanders on Thursday consuming 433 megalitres - up on the seven-day average of 427ML and well above the target of 420ML, with storage levels now down to just 42.9 per cent against a historical average of 77 per cent.
Stage 1 restrictions are designed to drop overall usage 5 per cent with bans on outdoor water use - such as hoses and water blasters, and calls for all residents and businesses to make voluntary savings.
Stage 2 is expected to be introduced when the dams hit 40 per cent, and will involve tougher savings requirements on businesses.
With the restrictions heavily impacting certain businesses already, particularly the exterior cleaning industry, many have criticised Watercare - the region's water supplier - for a lack of system capacity to handle the shortage.
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There has also been criticism of the Resource Management Act, with an application from Watercare to increase its daily take by 200 megalitres a day (MLD) - up from 150MLD - lodged back in 2013, and still languishing at 96 in the queue.
But chief executive Raveen Jaduram said the organisation was operating to drought response standards set by the region's leaders following the drought of 1993/1994.
At the time the water supply system was designed to handle a one in 50-year drought, Jaduram said.
Amid the public outcry that followed as dam levels dropped to 32 per cent, the system was upgraded to handle a one in 200-year situation - meaning once every 200 years, without restrictions, Auckland's storage dams could run dry.
They currently hold about 220 days' supply - based on the 2019 consumption average of 440MLD.
The city would never totally run out of water though, due to the far more secure Waikato River take, but supply would be down to about a third of normal levels.
So as not to run the system completely dry, Watercare applied a one in 100-year scenario for the dams to hit 15 per cent storage.
Complicating things further, there was no knowing when a drought would begin, nor end.
"That is the system we have," Jaduram said.
"There are comments there has been mismanagement or underinvestment, but it is occurring to the standard, to protect us from a one in 200 year drought event.
"At this stage we fear it could be worse than that."
The 2013 consent application for 200MLD was for long-term planning, and not for drought resilience, meaning based on their standard they did not require it at present, Jaduram said.
The same applied for the recent application for an extra 100MLD.
Even the extra 25MLD Watercare can draw from the Waikato River when it is above median levels - generally May to September, was superfluous to meeting the drought standards, Jaduram said.
Despite being granted consent for the take back in 2017, Watercare only started upgrading its capacity to treat the extra take in April, expected to be finished by August.
It could not draw the water presently as the river was below median level, but it could have last winter.
"In hindsight of course I wish we had been drawing as much as we could last year, but again it was not required as per the standards."
The drought standard model meant to prevent the dams running dry there needed to be restrictions.
"To have such a system that did not require that, we would need nearly 100 per cent redundancy just sitting there," Jaduram said.
"The sentiments we are getting is that if there is no rain we should just turn the tap on from the Waikato.
"If that is what Aucklanders want, then councillors can set that standard, but it will mean more infrastructure and permits - more money."
To upgrade the Waikato Water Treatment Plant to handle the extra 200MLD is expected to cost $291.4 million.
So to delay those costs, Watercare has been encouraging water efficiency.
In 2004, Auckland was using 298 litres per day, per capita - including commercial and residential.
Based on that rate, the new Waikato River water source would have been needed in 2021.
In 2008, Watercare, in collaboration with Auckland's former local councils, set a water efficiency target for the region of 253 litres by 2025.
Doing so would defer the need to increase supply another 10 years, to 2031.
Auckland had been on track to meet that target, but the increasingly dry weather was pushing up demand, and there have also been suggestions Watercare's models have not properly accounted for the city's population increase.
Under Watercare's 2018 Asset Management Plan, the next water source was not required until 2028.
This was based on water consumption in 2017 of 400MLD rising to 460MLD by 2028.
But in 2019 it had already jumped to 440MLD.
Jaduram said this increase was largely due to another very dry start to the year. When it's dry, people tend to use more water, including watering their garden and washing their cars.
The same was likely for this year also, Jaduram said.
But he also believed their population estimates could be slightly off.
There were factors including more households on tank supply in dry years refilling from Watercare's supply, and fluctuating tourism levels.
"I have a feeling the population in Auckland is higher than the official numbers tell us, based on water use."
Jaduram said the population trends and water capacity forecast was reviewed each year, and likely the 2028 target would need to be brought forward.
Regarding the current situation, Jaduram feared restrictions could be in place through next summer.
He expects dam levels will not get any higher than 70 per cent before next summer, so if it is another dry one, the region could be in major trouble.
Jaduram said he felt for businesses hit hard by the restrictions, especially coming out of the Covid-19 shutdown, but they had to draw a line somewhere, and that was on outdoor use as they were able to monitor it.
Watercare and the council was working to provide recycled water as quickly as possible.
"But I'd also say stand back, come summer and we are facing major shortage, and we'd allowed people to continue washing buildings, houses or filling swimming pools, we would be responsible for that. Our role is to look after water for all of Auckland."
Practically speaking, it was impossible to say how much rain was needed to get back to normal levels, Jaduram said.
"In lay terms, we need a bit of rain every day until summer. And we need everybody to do their bit to save water."
Despite restrictions coming into force Saturday, Auckland's water use has hardly dropped.
On Thursday Aucklanders consumed 433 megalitres (ML), above the average for the past seven days of 427ML, but down on last Thursday at 447ML.
There have been 345 complaints about restrictions breaches.
To address the short-term shortage, Watercare was also getting Hays Creek Dam in Papakura running again, and re-establishing a mobile treatment plant at a bore in Pukekohe.
Auckland's council-owned and operated swimming pools are remaining closed due to the water restrictions.
Auckland's water shortage
• Stage 1 water restrictions will be in force from May 16 and prohibit the residential use of outdoor hoses and water blasters unless for a health, safety, emergency or biosecurity reason.
• Under stage 1 commercial car washes are also banned unless they use recycled water; and watering of sports fields, plants or paddocks is restricted to those with an irrigation system fitted with soil moisture or rain sensors.
• Watercare further advises residents to keep showers short - four minutes or less, and only run the dishwasher or washing machine when they're full. No restrictions apply to hygiene measures, and people should continue regularly washing their hands consistent with Covid-19 messaging.