KEY POINTS:
Warning devices to alert authorities to any major breach in the new dam in Mount Aspiring National Park will be replaced tomorrow by better systems, officials said tonight.
One will build a 3D image of the dam and show changes.
An enormous recent landslide blocked the Young River north branch and created the dam.
Behind the dam a 2.5km-long lake formed, about 500m at its widest point and 100m deep just behind the face of the rubble dam.
Rising water flowed over the top of the dam late last week and on down the river, joining the Makarora River further down stream.
Officials said the lake and dam situation had changed little in the past 24 hours.
The flow over the top of the dam had been as wide as eight metres but this had not affected the dam's structure.
DOC Wanaka area manager Paul Hellebrekers said in a statement heavy rain fell at the weekend, testing the dam.
"It's come through that okay and we now have to look at longer term systems that will keep us and the community informed."
Consulting geologist Jeff Bryant said even though the structure had withstood three days of water flow over the top, "there are still good grounds for a high state of preparedness".
Mr Hellebrekers said the current three radio sets warning system was not sustainable long-term and different systems, not needing round-the-clock monitoring, were being examined by the Otago Regional Council.
GNS S cience will install two recording systems tomorrow.
One will go into the lake and record level fluctuations. The other involves laser technology that will build a 3D image of the dam to show any changes over time.
Mr Hellebrekers said the Young Valley would certainly be closed until the end of October and the fishing season on the Young River might be affected.
The Gillespie Pass tramping circuit was closed until further notice.
- NZPA
