Lake Wakatipu yesterday afternoon. It has changed colour
following the massive slip at Sandy Bluff, above Chinamans
Bluff, on Saturday afternoon. Photo by Tracey Roxburgh.
The massive landslip in the Dart Valley has changed the
colour of Lake Wakatipu - temporarily, at least.
Queenstown Lakes District Council harbourmaster Marty Black
said the change in water colour was ''quite noticeable''
following Saturday's slip, becoming a ''more turquoise''
colour, similar to Lakes Tekapo and Pukaki, near Mt Cook.
While heavy rain in the headwaters had caused water to look
like ''pea soup'', Mr Black said there was ''no question''
the lake had already changed colour.
''Across the lake from Cecil Peak towards Kelvin Heights [the
other day], you could see a distinct line from the real blue
to the turquoise.''
The phenomenon had been caused by the glacial rock falling
within the Te Koroka/Slip Stream area at Sandy Bluff, about
10km above Chinamans Bluff.
While Mr Black said he had asked if the lake would return to
its previous colour, he had been told it would but ''not in
However, GNS principal scientist Simon Cox doubted the colour
change would be anything more than temporary.
An ''awful lot'' of fine glacial ''flour'' had come down the
face of the slip and into the lake, where it was being
suspended in the water, refracting the light.
In lakes like Tekapo and Pukaki, the glacial flour was so
fine it was unable to flocculate together and sink, remaining
suspended in the water.
Fine glacial flour in the Dart River slip. Photo by GNS
Mr Cox said GNS had noticed the colour change and some
people had become interested in whether the lake would ''become
like Lake Pukaki''.
While the slip material had not been tested, he suspected the
glacial flour in Lake Wakatipu would not be fine enough to
''You might have something like that temporarily, but I would
be very surprised if it was permanent, so perhaps enjoy it
while you can.
''The lake is really big, you've got a huge amount to get
scattered ... I suspect the [landslip] is not big enough to
sustain that amount of material in the water over a long
period of time.''
Mr Cox said GNS was still working to establish the volume of
rock that came crashing down about noon on Saturday, which
had formed a new lake upstream of the slip. He believed more
material came down early yesterday, increasing the slip's
ability to dam the river for a while. However, the river flow
had increased again by noon.
''There is still stuff coming down, as you would expect.
''There's a tussle going on up there between the land[slip]
delivering concrete-like material ... and the river's ability
to take that away.''