Heavy rain over the past two weeks has brought a silver lining for some North Otago farmers.
While the rain at the end of May and again last weekend flooded some farms, it also brought relief for farmers irrigating from the North Otago aquifer.
The aquifer provides groundwater for irrigation of farms in the Waiareka Valley through to the coast south of Oamaru.
Before the rain, the aquifer's level was only centimetres above the limit at which irrigators would have had to reduce irrigation by 25%.
Now, water levels in the aquifer are at a 10-year peak, Otago Regional Council environmental information and science director Dr John Threlfall said yesterday.
The aquifer is "more or less full" for the start of the next irrigation season.
Before the rain, aquifer levels at Deborah had been dropping because of the autumn dry spell, causing concern to many in the district.
Dr Threlfall said the rapid changes began late on the evening of May 24 when the Kakanui River spiked upwards under the torrential rain.
Within four hours, the groundwater level had responded to the recharge, such was the intensity of the rainfall.
The groundwater rose sharply with the two bouts of heavy rain, and finally peaked on June 2 as drainage of overlying soils reduced and recharge intensity eased.
The 1.7m rise was the sharpest and largest in the 10 years since August 2000, which was still the largest single recharge event recorded in 25 years, at 2.9m.
On Tuesday morning, the third heavy burst of rain in the area since May 22 pushed groundwater levels up by a further 300mm, taking the peak to 131m, a total increase of 2m.
Dr Threlfall said this had the positive effect of significantly replenishing the aquifer and forestalling the possibility of irrigation restrictions for several months.
The groundwater level rose in a staircase fashion, with each step punctuated by a new burst of rain.
The total rainfall at The Dasher rain gauge from May 22 until Tuesday was 423mm, about half of which soaked through the soil into the aquifer below, Dr Threlfall said.
The rest of the rain would have run off and contributed to flooding, he said.
Rainfall of up to 55mm at the weekend - usually not a problem - ran off quickly and caused further flooding in North Otago.
Yesterday, the Waitaki District Council had 17 road-closure notices in place due to flood damage and Dansey Pass was closed because of snow.
State Highway 1 at Hilderthorpe, north of Pukeuri, reopened yesterday morning.
Four water schemes were not operating because of discoloured water at pump intakes, while others had notices to conserve or boil drinking water.
