In 1992, Central Otago conservationist Lewis Verduyn-Cassels and friends undertook a rafting expedition of the Clutha River, the last time the entire river would be fully navigable before the Clyde Dam was commissioned. In so doing they passed through the dam itself via the low-level diversion sluice, a never to be repeated feat.
All of the photos below are from the Terminator92 blog (see link at the end). Please note I was not able to find out how to contact the blog's owner to request permission to use these photos. I am happy to talk to Lewis if I can find out how to do so.
The bridge at Lowburn was left to be flooded by Lake Dunstan and is still there today, 13 metres below the surface.
Just upstream from the Cromwell Town Bridge of the 1860s. This was also left in place around 11 metres below the lake surface after the decking had been removed. The landscape of the Gorge has been radically altered due to slope stabilisation work needed as part of the hydro project.
Preparing to pass through the Clyde Dam. The four gates for the generator penstocks are to the left, while the diversion sluices through which the river flow passed during construction and lake filling are seen to the right. A few months after this photo was taken, the lowest level of these sluices was closed to start filling the lake.
Entering the low level sluice. These were the first part of the dam completed, being designed to allow the river to be diverted away from the main dam body allowing dry riverbed construction. Views of the dam today show no obvious evidence of the mechanical linkages and machinery used to operate the control gates, which may have been permanently closed with concrete during the lake filling (as was done at Waitaki). However one of these gates has been retained to draw down the lake in the event of risk to the dam or maintenance requirements.
Exiting from the dam downstream. This scene is much the same today, except that the diversion channel is closed and therefore calm; all water now flows from the tailrace below the generators or the spillway - at the far side of the bridge in the distance.