5. The Clyde Dam
Later, at the end of the gorge, the Clyde dam loomed skyward – mammoth, monolithic.
Clyde dam, from upstream before the inundation.
Approaching the dam, and the diversion channel (right).
In the 1980s, the then National government's 'Think Big' agenda brought massive upheaval as plans for New Zealand's largest concrete gravity dam moved ahead, despite widespread protest.
The exploitation of the Clutha for maximum power at any cost, was driven by departmental and political ambitions that would prove too insidious to be checked, even by the courts. The inexorable weight of the NZED (New Zealand Electricity Department) and the MOW (Ministry of Works), coupled with a secret deal made by naive government ministers providing COMALCO (Rio Tinto) with cheap electricity, set the agenda and fuelled the official lust for power.
During construction of the dam, the bed-rock was found to be microfractured because of a major earthquake faultline - the River Channel Fault. Pre-dam investigation work had been inadequate, and dam safety issues became the focus of heated public protests.
Threatened landowners went to the High Court in 1982, winning their case against the Government. But the democratic provisions of the New Zealand legal system were over-ruled by the Government, lead by Prime Minister Robert Muldoon, and the dam went ahead, in what can only be described as one of the most shameful chapters in the history of New Zealand.
The dam was redesigned in two halves with an experimental "slip-joint" intended to allow two metres of lateral movement, and one metre of vertical movement. One of New Zealand's leading geotechnical scientists, Gerald Lensen, warned that the River Channel Fault was a secondary "tensional fault" (expanding), and therefore the "slip-joint" was not designed correctly. Despite compelling evidence supporting Lensen, he was ignored. He resigned in protest and the issue was covered up.
In 1986, landslide stabilization problems halted the project while numerous experts debated safety issues. But the Government was determined to proceed at any cost, and 18kms of drainage tunnels, with 24-hour pumping and monitoring stations, were embedded in the landslide zones of the gorge. A massive cost blow-out brought the total cost to nearly $2 billion, amidst continuing controversy over the dam's safety, viability and necessity.
In a matter of months, the gorge we had just rafted would be silenced as the reservoir behind the Clyde Dam began rising. The reservoir would be filled in three stages between 1992-93, gradually flooding the spectacular Cromwell Gorge, the historic heart of Cromwell, many orchards and homes, the settlement of Lowburn and the surrounding fertile farmland - a total of 2300 hectares of the best orchard and farmland in Central Otago.
The lifespan of the dam is estimated to be 80 years, but opponents doubt that it will survive that long, given the ongoing instability of the Cromwell Gorge, the risks posed by earthquakes and landslides, and the speed of reservoir sedimentation.
The river near the dam would be inundated beneath 60 metres of "dead" water. We pulled in before the diversion channel and walked up to scout our route through an open sluice-gate beneath the dam. At the present flow level it was navigable with ample head-room. The raft slipped quickly into the black hole, and a million cubic metres of concrete closed over us like a tomb. Here, above us, was the real "terminator." Ahead, a beacon of daylight pierced the gloom, and within moments we emerged into what felt like another river.
Approaching the open sluice-gate.
Entering.
*#%*@#*!
In the "tomb".
Exiting in the diversion channel.
Looking back, and up.
By 6pm, we had reached Alexandra, in the heart of the semi-desert.
