The banks of Lower Huia Dam (23rd June 2020)
The latest long-range weather forecast predicting a very dry second half of 2020 has elevated Auckland’s water supply situation to a critical level.
Our total dam storage is currently 44.98%, where normally it would be at about 78% for this time of year. From November 2019 to May 2020, Auckland received less than half the normal rainfall, which has led to outdoor water restrictions being put in place for the first time since the 1993/1994 drought.
MetService meteorologist Georgina Griffiths says long-range weather models have no good news for drought-stricken Auckland.
“The long-range models are sending a clear signal for a much drier-than-normal spring period, between August and November, with a strong ridge of high pressure preventing the rain makers from crossing Auckland very often.
“This is the driest outlook for the spring season we’ve seen since 2013, when a major drought affected the upper North Island.”
Watercare chief executive Raveen Jaduram says the forecast has moved Auckland’s water supply status to ‘critical’. “We have been hoping for significant rainfall to replenish our dams, but the latest weather outlook indicates we’re in for just the opposite – more dry weather for spring and early summer, in what has already been a record-breaking dry year.
“But of course keeping our fingers crossed for rain is not all we’ve been doing. We are leaving no stone unturned in our quest to find more water sources or expand existing ones.
“Last week our board signed off on an urgent upgrade of the Onehunga Water Treatment Plant, which will deliver an extra four million litres of water a day (MLD) by September.
“We have already invoked our emergency powers under section 330 of the Resource Management Act to treat a further 15MLD from the Waikato River. This means we are now treating up to 165MLD at our Waikato treatment plant, and in August, when a new network reservoir is completed in Runciman, this will increase to 175MLD.”
Work is also underway to bring back to service two former water sources – the Hays Creek Dam in Papakura and a bore in Pukekohe. Site establishment works have already begun at both of these locations and building consent applications are being prepared.
The Pukekohe bore project is on track for delivery of an initial 2.5MLD in August, and a further 2.5MLD in December. Modular, mobile treatment plants are being built inside shipping containers. Hays Creek Dam will be supplying up to 6 million litres a day by December.
These projects will provide an additional 40MLD to Auckland, and will slow the storage decline of Auckland’s nine dams in the Waikākere and Hūnua Ranges, which normally supply about two thirds of the city’s water.
“To put that in perspective, that 40 million litres a day would supply a city the size of Dunedin,” Jaduram says.
Desalination has also been investigated but it is not a preferred option due to the cost and environmental impact.