Hamilton City Council is preparing to raise its water alert level if residents don't cool off on their usage.

Hamilton has been on water alert level one since the start of December, which means residents can only use their sprinklers during 6am and 8am, and 6pm and 8pm.

On Tuesday, Niwa meteorologists released their three month predictions of weather in 2019, with less than average rainfall expected for the north side of the North Island.

This, combined with above average temperatures predicted for the North Island, has led council to anticipate higher water usage in the city, with residents returning from their holidays.

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City Waters manager Maire Porter said the council has already seen a spike in water usage this week.

"We traditionally see lower levels of water usage for the week of Christmas, as people travel outside the area for holidays, but there is a significant spike when people return.

"We have seen daily water usage increase around 14 per cent this week compared to last week, and we anticipate further rises in usage as the hot weather continues and more people return from holidays," Ms Porter said.

"Outdoor water use is one of the big drivers for water consumption early in the year and if the hot weather continues as forecast, and people don't continue to be careful with how they use water, we could see changes in the alert levels.

"There's 160,000 people in Hamilton — if everyone ran the shower for 30 seconds less each day that's more than a million litres saved."

Last year Hamilton reached water alert level two, which has households using sprinklers on alternating days between 6am and 8am, and 6pm and 8pm.

Ms Porter said the council decides on changing the level based on numerous factors.
It took until March 2018 for Hamilton to be eased completely off water restrictions last year, only dropping back to level one during the middle of February.

"These include current and historical water usage data, weather forecasting for the Waikato and Lake Taupo water levels.

"The river level changes depending on how much water is released from Taupo for the hydro-electric system and only impacts our supply of water if it drops below our water intake structure. Should this happen, we have built a special floating platform which can pump water from a deeper part of the river.

"The biggest driver for water alerts is how much we are using, as we have limits on how much water we can take from the river and how much water we can sustainably treat each day at our water treatment plant. High quality drinking water is a precious resource, and that's why we ask people to be mindful about how they use it."

Last year, council told Hamilton News the growth of Hamilton is adding more pressure on the city's water assets.

"As Hamilton is growing, more and more pressure is going on our water assets. We need to ensure we don't overinvest in water treatment infrastructure for the few months of the year when there is particularly high demand.

"At the same time we need to upgrade existing infrastructure to make sure that it can keep up with demand. We have also been improving the reliability and supply of water around the city with the new reservoir in Rototuna, and another one planned for the Ruakura area. The council's Long-Term Infrastructure strategy identifies that a new water treatment plant costing in excess of $100 million will be needed from 2045, and could be required sooner if we don't continue to manage our demand for water responsibly."