Water demand peaks during restrictions
As Wellington faced the threat of a water emergency, the city’s demand for water hit its peak, new data shows.
But according to Wellington Water, it was news to be applauded as modelling had predicted the city would need even more water.
The water utility releases a weekly leaks report which shows how much water demand – made up of water use plus leaks – but this data stopped at the end of 2023. After queries from The Post, Wellington Water has now released all the data.
It shows that throughout the second half of 2023, water demand was higher than at the same time in any of the previous three years.
Around early to mid-January it begins to rise. This was about the time that the city was about to move to level 2 restrictions, meaning gardens could only be hand-watered while residents were pointing to hundreds of leaks around the city.
It was also about the time Wellingtonians were queueing for hours to get limited supplies of rain water tanks, and around when Local Government Minister Simeon Brown summoned Wellington and Upper Hutt mayors to a please-explain meeting about the water crisis.
By about the end of February, the city’s water demand was higher than it had been at any time in the four-year period the Wellington Water data covers.
Councils around the region were digging deep, and boosting rates, largely to get money in their long-term plans to fix failing pipes. It was also around the time the city avoided level 3 water restrictions, dodging a ban on most outdoor water use.
Through later March – as it was revealed that the cost to fix a leak in Wellington City had risen from $1500 to $4932 in three years – water demand slowly dropped and by about May it had dipped below the previous year.
Wellington Water in May said the residents of Wellington City, Porirua, Lower Hutt and Upper Hutt saved more than 175 Olympic-sized swimming pools of water over summer.
What the statement did not say was that the savings were against predicted use, based on modelling, as opposed to previous years.
Chief drinking water adviser Laurence Edwards said variables meant it was hard to compare summers. Last summer had Cyclone Gabrielle and before that was Cyclone Dovi in 2022 – both which lessened the need for restrictions.
Wellington Water has now supplied the two sets of modelling Wellington Water got before summer. They factored the effect of the climate on demand.
Comparing demand against a Stantec model, Wellington saved 400 million litres and, against the NIWA model, 1.6 billion litres.