Photos: Landslide and newly-formed lakeKEY POINTS:
The South Island's newest lake is on the rise, with the water level nearing the top of the bank after heavy rain overnight.
The lake was formed after a landslide created a natural dam on the Young River that winds its way through the Mt Aspiring National Park.
Queenstown Lakes District Council's emergency management officer Brenden Winder said it was now snowing in the area and the dam is coming under pressure.
"The chances of it happening tonight are reasonably good," Mr Winder said.
Department of Conservation spokesman John Gordon said a civil emergency plan for the small community at Makarora has been organised if the dam bursts.
Millions of cubic metres of water could rush down the valley if the dam bursts.
Staff from DoC, the Otago Regional Council and the Queenstown Lakes District Council visited the lake this morning by helicopter.
Mr Winder said the last part of the lake will put the most pressure on the dam.
"It went up this morning after first light but it's rising slowly because the last bit will take the longest," he said.
The council has installed radios in the likely path of the dam breach and is monitoring the radio signal.
Mr Winder said another helicopter flight will be made late this afternoon and at first light tomorrow morning.
Photographs taken of the valley are postcard perfect.
"If it stays where it is and ends up being a lake then it will be spectacular," Mr Winder said.
One farmer has been relocated to the other side of the river in case the dam breaks but Mr Winder said he was in little danger.
Metservice is warning that 50mm of rain could fall in the area today.
Otago Regional Council's director of engineering Gavin Palmer said there was some seepage of water at the toe of the dam but with the bad weather, it was hard to know how much of that was rain run off from the surrounding hills.
"The weather is pretty poor with low visibility and heavy rain," Mr Palmer said.
He said nothing was guaranteed and it was possible the lake could become permanent.
"There are examples of lakes that have become permanent features but it is more likely that it will scar and change form," Mr Palmer said.
But he said with rain continuing to fall and snow covering the catchment area, the chance of the lake over-flowing its banks was increasing all the time.
