THE 'Mighty Clutha' forms the heart of one of the world’s most unique waterways. It traverses the dramatic semi-desert landscape of Central Otago, in the South Island of New Zealand, but the most spectacular river gorges, and much more, have been destroyed ... by dams. This is the unofficial story of the Clutha Mata-Au River and its stolen treasures. It is a story steeped in bitterness, shame, destruction, and sadness.

Clyde Dam Statistics

- Site chosen: 1976
- Construction: 1977-1993
- Commissioned: 1992-1993
- Type of Dam: Concrete gravity dam (largest in NZ)
- Dam Height: 102 metres
- Net Head of Water: 60 metres
- Width at Base: 70 metres
- Width at Top: 10 metres
- Length at Top: 490 metres
- Penstocks: 4 (plus 2 encased in concrete)
- Spillways: 4 with radial arm gates
- Sluices: 1 low level with radial arm gate
- Planned Capacity: 612MW
- Installed Capacity: 432MW
- Lost Capacity: 180MW (due to re-design error in 1982)
- Turbines: 4x Francis fixed-blade turbines connected to 108MW salient pole generators
- Total Concrete Poured: Approx. one million cubic metres
- Steel used in Penstocks: Approx. 1,350 tonnes
- Total Steel used: Unknown
- Weight of Dam: Approx. 3 million tonnes
- Annual Energy Generated: Averages 2,100GWh
- Reservoir Size: 26.4 square kilometres
- Reservoir Fill Time: 18 months (reached full operating level September 1993)
- Major Landslide Zones: 14 extending along the gorge from Cromwell to the dam
- Stabilisation Tunnels: 18kms of tunnels dug during gorge stabilization work
- Measuring and Monitoring Instruments: 6,500 originally installed
- Drainage Mitigation: 140 kilometres of drilling for drainage
- Landslide Buttressing: 5 million cubic metres of rock used in buttressing work
- Land Flooded: 2,300 hectares
- Operational Range of Reservoir: Between 193.5 to 194.5 metres above sea level
- Reservoir Storage Capacity: Described as "Not much"


Stabilisation Cost: $936 million (2005 value)

TOTAL Project Cost: $1.4 to 2 Billion (exact cost is unavailable or unknown)


Operation: The reservoir does not have much storage capacity, so the Clyde dam operates mainly on a ‘run of the river’ basis, with the average flow past the dam reflecting the natural flow of the Clutha and Kawarau Rivers. The expected variation of the reservoir is about 50cms. When inflows are low, storage at Lake Hawea is drawn down to compensate. The high dam option (Scheme F) was built supposedly to maximise generation and cost-efficiency. But the low dam option (Scheme H) could also have operated on a ‘run of the river’ basis with only 2% less output, avoiding the loss of old Cromwell, Lowburn, and a massive cost overrun. The low dam (Scheme H) would also have incurred fewer landslide issues, retaining 16kms of the original 21 km highway through the Cromwell Gorge. However, both options were inherently flawed, and were not defensible when measured against the geo-technical risks, landslide mitigation costs, long-term reservoir sedimentation issues and costs - including eventual decommissioning, loss of ecosystem integrity, and heritage and human costs.


By Molyneux Rush  

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About This Site

Cromwell before the Clyde dam was set to become a tourism icon. Blessed with a dramatic location, numerous historic buildings and a spectacular bridge overlooking the famous Cromwell Gap, its potential was obvious, until ... "think big."



The Roxburgh Gorge, too, with its many amazing rapids ~ the largest whitewater in New Zealand, had vast tourism potential, offering Alexandra and Roxburgh a booming industry focused on high volume whitewater kayaking, rafting and dory adventures unlike anything else in New Zealand.



The Clutha Mata-Au, before the Roxburgh and Clyde dams, possessed many natural treasures in the form of extraordinary river features and rapids.



This website tells the story of those stolen treasures, and records the bitter fight of ordinary New Zealanders pitted against arrogant government technocrats and politicians who considered the Clutha River ripe for exploitation at any cost.



Finally, the rising waters behind the Clyde dam submerged the historic main street of old Cromwell, the Cromwell Gorge including the famous Cromwell Junction, the Lower Kawarau Gorge including Sargood's Rapid (rated the best whitewater rapid in the world), the Cromwell Gap Rapid, the Lowburn area, and numerous orchards and homes. A total of 2300 hectares of productive land disappeared.



This website is a tribute to the Mighty Clutha, and to the many dedicated people who have fought, over decades, to protect its natural treasures.



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