Logs, driftwood and other flotsam in Lake Dunstan are expected to remain for at least five days, meaning those in boats - of all sizes - should take care.
Recent heavy rain has resulted in high water levels in the Shotover and Kawarau Rivers, which led to slicks of debris floating in parts of Lake Dunstan, particularly the Kawarau confluence.
Although there was noticeably less debris floating near the Clyde Dam late yesterday afternoon, Tony Smith, of the Clyde Coastguard, suggested people stayed off the lake.
''If they do go out, they need to use common sense. There is a lot of stuff floating about - trees, sticks and other stuff. But I think most lake users would know that.''
Dunstan Arm Rowing Club president Jacqui van Dam said she was likely to postpone her training on the lake and urged other rowers to be careful.
''I'm not going to go out in this. Because of the logs, I'll probably leave it a week. I've run over a few logs in the past. When you're rowing you're not looking at what's in front of you,'' Ms van Dam said yesterday.
Dan Druce, environmental adviser, Contact Energy, expects current lake conditions to remain for at least five days, ''although that depends on whether any additional rain falls''.
As part of its 2009 landscape and visual amenity management plan for the Kawarau arm of Lake Dunstan, Contact is required to remove driftwood from the Old Cromwell precinct area after significant flood events.
''And we have done that for a number of years,'' Mr Druce said yesterday.
''In couple of weeks, when the water flows have calmed down, we'll get some local contractors to go along and clean up debris.
''We have no responsibility for keeping Lake Dunstan clear of debris. However, at both the Clyde and Roxburgh dams, we have floating booms across the lakes that are angled. A log will hit the boom and will float across the lake.''
''Normally, driftwood doesn't have any effect on Contact's operations. However, it can occasionally get lodged against the penstock screens, in which case we'd use a crane to pull it free,'' Mr Druce said.
Earlier this week, Clyde Chief Fire Officer Richard Davidson pointed out that silting in the lake was also a problem, particularly after heavy rain.
''The silt debris gets dropped out of the Shotover and the Kawarau and it meets still water at the head of Lake Dunstan,'' he told the Otago Daily Times.
Mr Druce said Contact was in a long-term phase of monitoring the sediment build-up.
''Contact does not remove sediment from Lake Dunstan. The exception to this is at the Lowburn and Bannockburn inlets, where sediment is removed from time to time.
''The formation of the sand bars in the Kawarau Arm of Lake Dunstan are a recognised hazard. There are appropriate signs at boat ramps and in the river channel,'' Mr Druce said.
