Lack of rain in the mountain catchment has left the Wairau River low, Marlborough District Council hydrologist Val Wadsdworth said.
And summer storage capacity on the plains has been found wanting as a result.
January rain of 18mm was soon sucked up by 30C plus temperatures in February.
What is hurting grape growers most, however, is the record duration of irrigation switch-off.
Wairau River flows are tracking in a similar vein to 2001-02 when irrigation takes for Class A consents were off for 19 days then 14 days.
The difference is that this is now a 28-day streak and counting.
And it’s a time when vines really need water to feed berries so the stakes are higher.
There are now 2000 hectares of vineyards in the Wairau Valley, where in 2002 there were no grapes, and an extra 1000ha in the Southern Valley area, Wadsworth said.
Farmers without sufficient storage or aquifer back-up have resorted to carting water to keep sauvignon blanc crops worth around $24,000/ha from shrivelling.
Carted water costs at least $13 a cubic metre, a big step up from the $0.24 a cubic metre charged for water from the Southern Valleys Irrigation Scheme.
A 15ha block carrying $375,000 worth of fruit can shed up to 40% of yield worth $150,000 if seriously under-watered.
The Wairau River dropped below eight cubic metres a second on February 2, triggering switch-off for 60 users.
They included one big user, the high-pressure piped SVIS, which services about 300 properties covering 4680ha, including more than 2000ha of grape crops south and west of Blenheim. Thirty Waihopai River users were affected when Class B takes were stopped January 31.
Two attempts during the 2000s to build a dam for all SVIS users or add extra height to the existing Delta Dam did not attract enough support from subscribers in the Southern Valleys zone.
Some growers already had permits for aquifer takes while others built small dams, some of which are nearly empty now.
Wadsworth said increasing aquifer allocation is not an option because they are already over allocated.
“The Ben Morven aquifer dropped six metres at the end of January.”
Growers are tightly restricted in taking stream water for dams, meaning dam water has to be filled from existing irrigation schemes at a cost. Between 1995 and 2008, 120 permits to dam water were granted by the council.
“Ponds to store water from an irrigation scheme or rivers at high flow are the way to go,” Wadsworth said.
There are 20 storage ponds in the SVIS area but about a third of users don’t have back-up.
M and J Gibbons truck firm owner Murray Gibbons has been topping-up dams and pumping into storage tanks since Waitangi Day.
“Two clients have tanks on the vineyard while seven have dams that are emptying fast so we are topping them up.
“Since the scheme went off I’ve had five trucks carting up to 24,000 litres although I’m also needed for shifting wine.
“A shortage of drivers is a problem. I’ve even roped in a mate from Timaru.”
Gibbons said he’s had desperate growers at his door, which he describes as heart-breaking.
“One guy had just bought a vineyard and needs a crop or he’s out financially.
“Our community depends on the grape guys having a good year.”
Trucks have been sourced from out of town to meet demand.
One vineyard has installed a 100,000 litre bladder on a pad to store water, he said.
The council has provided a temporary water fill-up site at Riverlands Industrial Estate, which typically has a queue of three trucks.
“It’s going to be a perfect storm when harvest gets going next week with trucks needed for wine going out, juice coming in and water been carted,” Gibbons said.
Yellowing of leaves, shrivelling of bunches and, in the worst case, complete defoliation of the ripening powerhouse canopy can be seen in the district. Australian research shows expected yields can fall by up to 40% if vines are water stressed from veraison (the onset of grape ripening and colour change) to four weeks post-veraison from a lack of cell enlargement in the berries.
Farmlands technical adviser Lachy Hynd has 80 vineyard clients and describes the blocks without back-up storage as in trouble.
“If you can’t water, sugar levels don’t increase and berries remain rubbery balls at low brix (sugar content).
“Options are being discussed like cutting off a cane, sacrificing one block to direct more water to other blocks on heavier soils or harvesting earlier at lower brix.”
His clients with water are having a great ripening year while others are talking about extending storage dams next year.
Not a drop
IAN Anderson hopes his 3.6 hectare block of pinot noir, chardonnay and gruner veltliner grapes will bring in $90,000 this vintage.
However, consistently low flow in the Wairau River has seen the Southern Valleys Irrigation Scheme, servicing 4680 hectares, off for a record 28 days.
No reprieve of even two or three days means he has been unable to top up his dam to give the vines the best chance to yield well.
Four litres a vine every second day is about half of what’s needed, he said.
Anderson also manages blocks for 10 other growers and one of them has no storage or aquifer allocation back-up so yield loss is expected.
Even a 20% drop in yield means $5000/ha less income.
“Like other growers I’m looking to increasing storage capacity next year by recommissioning an old dam.”
It’s chalk and cheese. Last February he had 200mm of rain.
