Residents are being asked to change their water use behaviour. Photo / NZME
Tauranga may face its worst water shortage in recent history in the coming months as streams that supply the city's drinking water run low.
Tauranga City Council says residents may face longer and "stricter" water restrictions than previous summers and should start being more mindful of how they use water — perhaps even not flushing after "number ones".
Council staff also warned the under-construction $115 million Waiāri water treatment plant was no longer considered the "silver bullet" to help cope with surging demand and depleting water sources.
In a Strategy, Finance and Risk Committee meeting yesterday, council commissioners were told flow volumes in the streams that supply the city's drinking water were significantly lower than normal after three dry summers, creating a new issue: a lack of water available to treat.
The city was also experiencing increasing water demand due to growth and development.
General manager of infrastructure Nic Johansson said this meant council staff were planning to put in "stricter" water restrictions this summer. These were likely to land earlier and last longer.
"We are vulnerable and need to look at all the options," Johansson said.
These restrictions were expected to be finalised and released next week and were likely to be escalations of sprinkler ban rules used in previous summers. But it was hoped the city would not need to reach that point.
In a report presented to the council, Johansson said the Waiāri water supply scheme, due to be completed late next year and supply about 35,000 homes, was "no longer the silver bullet to resolve all our water supply problems".
The council's primary challenge had moved on from infrastructure capacity to one of environmental capacity, he said.
Tauranga's water supply comes from two spring-fed streams, the Tautau and Waiorohi, and is treated at plants in Ōropi and Joyce Rd. Water flow, particularly in the Tautau, has been at a low level and has not recovered.
It warned water supply would come under "significant pressure" in the next four to eight months due to the low levels of the Tautau, which supplies more than half the city.
A third water treatment plant is being built along the Waiāri Stream in Te Puke to help cater for demand, particularly for the growing Pāpāmoa and Te Tumu strip.
But the Waiāri steam flow was also declining - a climatic effect that had highlighted the council's "lack of resilience".
At the meeting, Johansson said: "Long-term, Waiāri is a big deal to us. Obviously that has a shelf life as well in terms of dealing with the growth ..."
Commission chairwoman Anne Tolley asked what this meant for the upcoming summer.
A sprinkler ban was in place for 187 days last summer - running from December to June - compared to just 60 days the year before and 54 days the year before that.
"Last summer we had the longest water restrictions in Tauranga's recent history. We've got some mitigation - are you confident that's going to get us through this summer?"
Johansson responded: "Confident is a big word. We are adopting strategies that have been used in New South Wales, Australia."
"We can't make more [water]. We have the added complication now that the water is not there to treat, to put out."
Johansson said if the council began communicating with the community "early", it may be successful in getting people to become more mindful of water waste and alleviate some of the demand.
"Whatever it is, flushing after number ones, etc, lots of things we do automatically because water means not much to us. But in communicating the value of it we think we will find a significant change in the behavioural [response] to it.
Team leader of water services Peter Bahrs said the situation was not about making more water available; "it's about utilising the water we have in the best matter".
"It requires us to think about the future. Therefore, what are the alternatives?"
Proposed "mitigation measures" included diverting to reduce demand on the Tautau; working with industry and commercial users for more efficient water use and better educating and explaining to the wider community the need for restrictions.
Questioned by commissioner Shadrach Rolleston as to whether the council planned to keep drawing on the declining streams, Johansson said it did.
"In the meantime, we will look at what our options are."
Long-term, the council was seeking a wider strategic partnership to co-ordinate and consolidate information and investment; seeking commission of research into the decline; and developing a Freshwater Management Tool with Bay of Plenty Regional Council to potentially predict future changes based on intervention options and climate change predictions.
A NIWA seasonal outlook for November to January predicts higher than normal temperatures for the Bay of Plenty, with normal rainfall.
The council was forming a water task team to manage the water supply and demand.
In a press release last week announcing it was preparing a new water conservation strategy, the council said it had resource consents from the Bay of Plenty Regional Council to take a certain amount of water each day.
The city had 17 reservoirs that stored enough to provide a buffer during peak water use times, or to keep the city going for 24 to 48 hours in an emergency.
The city did not have dams, like Auckland's, and it would be "enormously expensive" to do so today and have "significant cultural and environmental impacts".
According to the council website, the city uses an average of 42 million litres of water per day. In summer this can rise to 57 million litres per day.
Bay of Plenty Regional Council was approached for comment.
"If you’re loyal to them, they will be loyal to you."