Sunday, August 14, 2022

Heavy rains top up the tank

Soils over much of the country are at or above field capacity and aquifers and storage are completely recharged after heavy rains.
Ashburton farmer Chris Allen and Ace have spent most of the week keeping stock fed on dry ground as surface water flowed through Allen’s farm, much of it from as far as 12km away. Photo Annette Scott

Up to 300mm of rain has fallen over most of the country so far this month, with NIWA figures showing soils in many areas are at or above field capacity.

Northland and coastal areas of Otago and Canterbury were hit hard by heavy and persistent weather in the past week, while other regions are welcoming a return to normal winter conditions.

Heavy rain caused states of emergency to be declared in parts of Otago and Canterbury last week, and rain has fallen on Northland almost every day during July, completely recharging soils, aquifers and storage.

For the North Island the mean temperature anomaly – by how much this July exceeded the 30-year average  – is 1.2-2degC.

The only regions of the island with lower positive anomalies, 0-1.2degC, are Southern Hawke’s Bay, Wairarapa and Greater Wellington.

South Island temperatures for July are up to one degree above the historical average.

But the month-to-date rainfall map is the most arresting.

About two-thirds of the country received 200mm or 300mm within the first 27 days of July.

Most of the remaining land area received 100-200mm.

A NIWA spokesperson said rivers, aquifers and groundwater sources have been recharged, which will comfort farmers, rural residents, irrigation schemes and town water supplies that tap those sources.

Higher temperatures in July were not isolated, but the result of warmer territorial waters and the La Nina effect that has persisted for some time.

Coastal South Island areas from Dunedin to North Canterbury bore the brunt of a slow-moving weather front last week.

In the 48 hours to 6pm Wednesday, Dunedin recorded 108mm of rain, yet just over the hill, the Taieri Plain had only 32mm.

Simon Williamson, who farms near Twizel, said he has never seen his property, Glenbrook Station, so wet after two snowfalls and two heavy rain events in recent weeks.

The second snowfall occurred on Monday, leaving 200mm of snow, which was followed by 70mm of rain, causing a heavy snow melt.

“It is thawing quite quickly but I have never seen it so wet, but I guess it’s the right time for it to come,” Williamson said.

The access road leading to several  Ashburton high country stations is expected to be closed until at earliest August 5.

North Otago is also extremely wet with Federated Farmers president Jared Ross saying 100mm has fallen on his Duntroon farm in the past 10 days.

This has taken his rainfall for the year to date to about 350mm, about the same total as for each of the two previous years.

Dairy farmers have started calving and although ground conditions are wet, so far feed is not an issue with plenty of supplementary feed available for purchase.

The federation’s North Otago sheep and beef section chair Ross Hay farms on coastal North Otago and said 65mm fell this week, causing rivers to flood and taking the total rainfall for July to about 190mm.

“We’ve had more rain in July than we have had for the rest of the year,” Hay said.

Southland and south and west Otago appear to be experiencing normal winter conditions, with most areas recording about 20mm during the recent storm event.

Almost three times the normal July rainfall is creating stock management challenges for David Acland and his team on Mt Somers Station in the Mid Canterbury foothills.

June rainfall was 40mm above average and July rainfall 240mm, up from the usual 95mm.

“The issue is not really the flooding but water logging. The ground is just saturated,” the Mid Canterbury Federated Farmers provincial president said.

“While everyone’s stock is in pretty good nick, livestock management is a big job.

“Winter feed utilisation has been poor and testing the budgets in spots.”

South Canterbury has been harder hit.

“Its 20mm feels like 50mm. July has been a long month, but we are on the run out of winter and on the positive it hasn’t been bitterly cold, just wet, and miserable working conditions. The grass will start to grow soon,” Acland said.

Mid Canterbury sheep and beef farmer Chris Allen is counting his lucky stars the Ashburton River stayed in its bed after his property was one of the worst hit in the May 2021 floods.

“Water is just oozing out of the ground everywhere after the rain events we have had this winter. The aquifers are full and there is nowhere for the water to go.

“We have dodged a bullet with the river, just this time, but the surface water that is flowing through my paddocks now has travelled down from 12km up country because there is nowhere for it to go.

“Luckily it’s dropping quite quickly but at the peak it was flowing like a river, out across the road and onwards down country.”

With another 160mm of rain forecast next week, Allen remains nervous about the state of the nearby Ashburton River.

Hawke’s Bay and Taranaki farmers are relishing what is seen as a return to a normal winter after several that were dry.

Parts of Hawke’s Bay have already had nearly 900mm, just shy of the 1100mm that fell for all of last year.

With lambing underway, the biggest concern is sodden ground conditions even though temperatures are warm.

Taranaki Federated Farmers chair Mark Hooper said rainfall has been slightly above average with more than 400mm falling since June.

The dry autumn restricted the making of supplements and Hooper said with calving underway that could put pressure on pasture cover.

The wet weather has made calving miserable on many Waikato farms with feed levels still tight following last season’s drought.

Speaking at an online webinar organised by the Smaller Milk and Supply Herds group, Bart van de Van said his farm has recovered well after the lack of rainfall left it looking pretty dire in April-May. 

The farm finally received some decent rain in May, and by June 1 pasture cover was about 1700kg of dry matter a hectare.

Today, those covers are about 2300kg DM.

“It’s phenomenal if you look back at how much grass we have grown over the last two months and we’re growing better than we ever have,” Van de Van said.

Whangarei Airport recorded just under 400mm for the month with four days left to run, and that is double the historical average for July but 40mm short of July 2021.

Puhipuhi in the hills north of the city had 328mm in the past week – but 200mm fell on one day, Monday, July 25.

Dairy and beef farmer Geoff Crawford, who farms a large area of the Hikurangi Flood Management Scheme, said flood banks and gates had worked as designed.

While he had 200ha under water he expects that to drain within three to four days and pastures to survive in the relatively warm temperatures.

Federated Farmers Northland president Colin Hannah agreed with Crawford about above-normal grass growth for the time of the year.

However, paddocks are so wet that cattle have to be stood off for long periods and machinery cannot enter.

“If it wasn’t for the rain, we would be sitting pretty sweet,” Hannah told the local newspaper.

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