Another mostly dry month

ODT graphic.
ODT graphic.
Significant rain is urgently needed in many parts of Otago to ease soil moisture deficits after another dry month, a problem which has been compounded by the onset of cooler weather, hydrological consultant Dave Stewart says.

While March was generally dry, heavier rain finally returned after a two-month absence but not until March 20.

Before that, a series of fronts and ridges of high pressure dominated.

"These fronts generally brought rain to the whole region but, apart from in the far south, falls were not substantial."

Temperatures also tended to be cooler by the end of March, with some frosts being reported late in the month.

From March 20 to 24, northwesterly winds prevailed, bringing heavy rain in the west but significantly drier weather east of the southern lakes.

Towards the end of the month, a front became stationary over the far south of the South Island and some heavy rain was recorded in the headwaters of Lake Wakatipu, but not much rain occurred further north or east of the lakes.

In North Otago, well below average rainfall for March were recorded. Total falls at the indicator sites (average monthly totals in brackets) were:
Waikoura 11mm (35mm), 69% below average; Oamaru Airport 14mm (30mm), 53% below average; Kauru the Dasher 19mm (48mm), 59% below average; Islay Downs 16mm (54mm), 71% below average; Palmerston 16mm (60mm), 76% below average;River flows were well below their long-term averages for March.

Farmers reported a dry, warm and occasionally windy month with little or no growth on non-irrigated land.

Some rain this month would still be useful in promoting a little growth before winter, Mr Stewart said.

"Many of the creeks and streams have dried up and rain is urgently needed to begin reducing the soil moisture deficit."

In Central Otago, rainfall totals were well below average for March.

Total falls were:
Lindis Crossing 28mm (48mm), 53% below average; Cromwell 11mm (24mm), 52% below average; Alexandra 12mm (25mm), 51% below average; average; Merino Ridges 9mm (35mm), 74% below average; Ranfurly 10mm (32mm), 70% below average; Tima 34mm (44mm), 23% below average;

Average monthly river flows were well below their long-term averages. A lack of rain, warm temperatures and occasionally windy conditions ensured the ground remained very dry, Mr Stewart said.

"The Central Otago region is currently very dry. Significant rain of at least 100mm is needed now to replenish soil moisture deficits."

In Lakes Wanaka, Wakatipu and Hawea and surrounding areas, more than 70% of the month's total rain occurred in the last 11 days of the month.

Total falls were:
Makarora Station 201mm (206mm), 2% below average; Hunter Valley Station 66mm (88mm), 25% below average; Hawea Flat 31mm 962mm), 50% below average; Routeburn Station 211mm (196mm), 8% above average; Queenstown 82mm (72mm), 14% above average;Significant falls included: March 1, Makarora 30mm, Glenfinnan 41mm, Queenstown 29mm; March 12-13, Makarora 153mm, Glenfinnan 124mm, Routeburn 121mm, Queenstown 45mm;.

Average March river flows were close to their long-term averages and were significantly improved on the previous two months. The highest flows occurred around March 22 and some rivers rose more than 2m.

Levels in Lakes Wanaka and Wakatipu began the month at 276.65m and 309.67m, 0.55m and 0.20m below average respectively. After an initial brief rise, both generally declined until March 21, when Wanaka reached 0.75m below average and Wakatipu reached 0.30m below average. Over the next few days, Wanaka rose 0.74m and Wakatipu 0.35m and, at the end of the month, both lakes were close to their average March levels.

Lake Hawea fell slowly for much of the month but by the end of March it had risen again almost to the same level it started the month at. On March 31, Lake Hawea was at 344.42m, about 1.6m below full.

Farmers around the lakes' headwaters reported conditions were a bit dry at the start of the month but were good now with reasonable growth. Away from the headwaters, conditions had been drier, especially around Lakes Wanaka and Hawea.

"A Hawea Flat farmer has reported the past season has been the driest and hardest since 1975/76."

In Strath Taieri, Lower Taieri and Dunedin, it was the eighth month in succession of below average rainfall.

Totals were:
Garthmyl Middlemarch 18mm (3834mm), 54% below average; Dunedin Airport 29mm (43mm), 33% below average; Dunedin Musselburgh 23mm (58mm), 61% below average; Lee Flat 34mm (60mm), 56% below average; Pine Hill 33mm (76mm), 57% below average;Other rain gauge totals included: Southern Reservoir 26mm and Sullivans dam 43mm.

Average monthly river flows were below their long-term averages for the month.

Farmers reported a very dry monthwith limited or no growth due to the dry conditions, he said.

"Rain is urgently needed to ease the dry conditions."

In South and West Otago, rain totals were well below average in all but the far south.

Total falls were:
Tuapeka Mouth 35mm (64mm), 46% below average; Balclutha 31mm (42mm), 26% below average; Waikoikoi 50mm (83mm), 40% below average; Slopedown 118mm (106mm), 11% above average; Clarks Flat 25mm (56mm), 55% below average.

All river flows were below their long-term averages for March. The exception was the Pomahaka, which showed some improvement during the month, and the Clutha, which improved markedly after March 23 due to significantly increased outflows from Lakes Wanaka and Wakatipu.

Farmers reported varying conditions, with some having slow growth either because it was too dry or too wet (far south). Others reported a great month for growth but most agreed rain was needed except in the far south, he said.

 

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