Northland dam levels rise but caution still needed over water use

Whau Valley dam at 58 per cent full in June. Photo / Michael Cunningham

Thanks to steady rain the Whau Valley dam level has been boosted by 1.5m but despite the rise officials are still urging careful use of water.

The dam supplies Whangārei city and is now at 58 per cent full but is still well below the normal level for this time of year. It had got as low as 45 per cent full by mid-April.

While in Ruakākā 50mm of rain was enough to see Wilson's Dam climb to 60 per cent full.

Whangārei District Council water services manager Andrew Venmore said the rain was a "godsend" but not enough to lift water restrictions in the city.

Whangārei District Council water services manager Andrew Venmore at Whau Valley Dam. Photo /File

He said one more rain event was needed before a change in restrictions could be considered and at least two more rain events like the one over the weekend to get back to normal.

"We would like people to keep saving water ... we still need to fill the dam before summer. That means water restriction level 3 is in force or the moment.

"The rain was a godsend, now we have to start building on that."

On Sunday 107mm of rain was recorded in Whangārei, which was the fourth highest daily rainfall for the month of May since records began in 1943.

And records showed that a total of 209mm for the month of May, with a May average of 110mm, was more rain than Whangārei had seen in the preceding six months.

Whau Valley dam at 58 per cent full in June. Photo / Michael Cunningham

Whau Valley dam at 54 per cent full in April. Photo / Michael Cunningham

Chris Brandolino, principal scientist for Niwa, said a good week of rain in Northland thanks to a northerly moist flow from the tropics had boosted rainfall figures for the month.

However, some parts of the region were still lacking much-needed rain.

Kaitaia recorded 90mm of rain - just over half the May average of 167mm. Kerikeri on the hand had 285mm of rain in May compared to 152mm May average. Kaikohe recorded 174mm which was above the average of 129mm for the month.

And where the rain was needed the most it failed to fall, with rain gauges in Dargaville collecting just 75mm rather than the May average of 129mm.

Winter officially began on Monday and Brandolino said predictions for the winter season could see rainfall reach average or below-average levels.

Federated Farmers Northland representative John Blackwell farms sheep and beef cattle on about 550ha south of Dargaville and had around 40mm of rain over the weekend.

It was gentle rain, so there was no runoff to damage the paddocks, but it was not enough to fill dams either.

While grass had started to grow much of the winter supplementary feed stockpiles had been fed out by farmers in the region.

Blackwell said as long as there was a mild winter the region could have grass growth through the season.

MetService meteorologist Andrew James said another low-pressure system would bring more rain today, before cold air moved in this weekend.

The rainmaker could also bring thunderstorms which could see localised rain falls of up to 25mm in short blasts.

A dusting of snow is possible for the southern ski fields over the weekend.

Ben Hope, KDC spokesman, said the dump of rain had seen river levels rise but long-range forecasts did not predict more consistent heavy rain events.

He said there would have to be some consistent rain before water restrictions were changed.

Northland Regional Council monitoring and hydrology team reports indicate rainfall for this year is currently tracking 40 to 45 per cent below normal levels across all the main centres in Northland.

Far North District Council communications manager Richard Edmondson said the weekend rain had improved soil moisture levels and water flows in key waterways, especially in east coast areas such as Kaeo and Kerikeri.

However, the rain did not fall evenly across the district, particularly in the northernmost reaches of the district, and in the mid-north and west coast where rain was most needed.

Staff were still gathering hydrological data after the long weekend and would decide todaywhether to recommend a further relaxation of water restrictions.

The Northland Regional Council advised last month that the district needs 900-1000mm of rain before October to avoid water shortages next year.

"We will need more rain events like that at the weekend, and rainfall distribution will need to be more even, before the drought is over," Edmondson said.

*Level 3 in Whangārei means households and businesses can now water gardens and wash cars, buildings and paved areas using a bucket.

Commercial car cleaners can also operate high-pressure and recycled water systems. A ban remains on the use of all outdoor hoses and irrigation systems. Filling swimming pools also remains banned.