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The Cromwell Gorge is a steep gorge cut by the former Clutha River (Māori: Mata-Au) in the Central Otago region of New Zealand's South Island. It winds between the Dunstan and Cairnmuir Mountains, linking the townships of Cromwell and Clyde. It is one of three substantial river gorges in Central Otago, the others being the Kawarau Gorge to the west of Cromwell, and the Roxburgh Gorge south of Alexandra.
Long-associated with gold mining, orchards and the production of stone fruit, the gorge (including part of old Cromwell) was flooded in the early 1990s to form Lake Dunstan behind the hydroelectricity Clyde Dam. The former Otago Central Railway which traced the river through the gorge from Clyde was removed, while State Highway 8 was realigned above the newly-formed lake.
The Dunstan Trail, a major new cycle route, was opened on the lake's right bank in 2021.
The Cromwell Gorge is the entrance to the Upper Clutha Valley and was historically an important thoroughfare for early Māori moa hunters, and later pastoralists and gold miners in the late nineteenth century. It remains an important access route into Central Otago's interior via State Highway 8 (SH8).
The Cromwell Gorge exits the Dunstan and Cairnmuir Mountains immediately to the north of Clyde. Both mountain ranges are controlled to the south-east by large reverse faults; the Dunstan Fault and Earnscleugh Fault, respectively. Investigations have found that geologically-recent deformation associated with the Dunstan Fault has extended south-west towards Clyde, rather than being translated along the southern margin of the Cairnmuir Mountains. This is important as it suggests that there is no recent activity on the transfer zone between the Dunstan and Earnscleugh Faults. This transfer zone is controlled by the well-documented River Channel Fault, a steeply dipping fault mapped as running down the centre of the gorge and directly beneath the Clyde Dam. The former Clutha River followed several of these faults as it coursed through the Cromwell Gorge.
Grassland and scrub now cover most of Central Otago. On the former valley floor of the Cromwell Gorge, low Tussock grass grassland of several varieties dominated, while manuka, kānuka and matagouri scrub patched the lower slopes. Uncontrolled burn-offs, over-grazing, and the introduction of the rabbit in the mid-1800s, have heavily modified the vegetation cover since European settlement. This is further worsened by Central Otago being the driest region in New Zealand. Those areas of the gorge which are the driest are dominated by cushions of scabweed, Rosa rubiginosa, and thyme, all of which flourish. The introduction of thyme to Central Otago is most-often attributed to Jean Desire Feraud, a French Placer mining and who was part of the Otago gold rush.
There is evidence of native plant regeneration (such as kōwhai) in areas where conservation has been put in place, though its reestablishment in the Cromwell Gorge is not nearly as extensive as the nearby Roxburgh Gorge. Forests of kōwhai ( Sophora microphylla) have recently been postulated to have also been present in the Cromwell Gorge, upon which moa grazed.
Today in spring and summer the gorge blossoms with wild flowers: the purple of thyme, the blue of Echium vulgare, the red of Spur valerian, and the yellows of Californian poppy and Sedum.
Evidence for Māori occupation of specific sites in the Cromwell Gorge was well-documented during the Clutha Valley Archaeological Project resulting from the decision to build the Clyde Dam. Despite the limited number of samples available, rock shelters and adjacent sites showed the following finds to be culturally significant:
It has been suggested that the numerous overhangs within the craggy rock formations of the Central Otago river gorges may have been favoured moa nesting locations. Such locations abound in the Cromwell Gorge and eggshell fragments found in many shelters confirm their usage. If early Māori hunters recognised such a regularity in moa ecology, it seems likely that they would undertake seasonal or regular raids on nesting areas.
Chalmers made his trip into Central Otago's interior when no roads or tracks existed, hoping to retrace the steps that his guide, Reko, had made from the Waitaki River some twenty years earlier. The trek from the Mataura River in Southland Region to Waitaki was some distance, climbing mountain passes in excess of something Chalmers was blissfully ignorant of ahead of his expedition. Unfortunately for Chalmers, he contracted a bout of chronic diarrhoea early into his trip and suffered with it for many weeks. Having eventually made it as far as Lakes Lake Wakatipu, Hāwea and Wānaka, his illness got the better of him and he realised he would not be able to make it to Waitaki.
In a letter to historian Herries Beattie, Chalmers recorded his account of the journey (some fifty seven years after the fact) stating that the shortest way back to Southland would be to build a flax fibre mokihi or raft and ride it all the way down the Clutha River. As they set off from Lake Hāwea and entered the Clutha Rive, Chalmers wrote that they:
Within half a day, they came to the Clutha's junction with the Kawarau River, leading Chalmers to write:
When they emerged from the gorge at the site of the present-day Clyde Dam, he wrote " then our troubles were over".
Chalmers' early foray into Central Otago was closely followed in the mid 1850s by early pastoralists and runholders searching for sheep grazing land in the vast, trackless interior. It was only after surveyor John Turnbull Thomson and Alexander Garvie lead a reconnaissance survey of the region in 1857-58, that pastoralists moved into the area in earnest; within a year of Turnbull's survey some had been applied for.
The winter of 1862 was exceptionally severe and resulted in unseasonably low-levels of the Clutha River. Horatio Hartley and Christopher Reilly worked the sides of the Cromwell Gorge for three months until they were forced to take the huge hoard of gold they had secretly amassed to the Chief Gold Receiver in Dunedin in August 1862. Hartley and Reilly's discovery caused great excitement as they deposited some of gold, sparking a gold rush to what would become known as Hartley's Beach. Hartley and Reilly, in divulging the location of their rich finds (approximately one mile downstream of the Clutha River's confluence with the Kawarau River), were rewarded with £2000 from the Otago Provincial Government. On 23 September 1862 the Dunstan goldfield was proclaimed, the selection of this name in preference to Hartley's being largely in deference to Reilly, who was 'jealous of the pre-eminence' accorded Hartley as the discoverer.
Within days of the announcement of Hartley and Reilly's discovery, 2000 miners had descended on the Dunstan goldfield with the first gold export to leave the goldfield on 6 October 1862 carrying some 6030 t oz (187.5 kg) of gold. Between 1 September 1862 and 1 April 1863, 120,886 t oz (3760 kg) of gold were recovered from Otago, with most of this coming from the Dunstan goldfield. By the end of 1864 the easily won gold had been mined and many had moved off to other more lucrative fields.
Many mined in the gorge where they lived a hard life in harsh conditions, often in rock shelters. The first camp established was near Gibraltar Rock () in the Cromwell Gorge, although a far more substantial settlement in the 1870s formed Cromwell's Chinatown. Deserted by the turn of the century, the wooden stores and businesses were demolished in 1930.
Chinese were not always popular or welcome, and often blamed for things they did not do. This was made more problematic due to the manner by which they were initially invited to New Zealand; the Chinese regarded themselves as temporary visitors seeking gold. As such they tended to have little interaction with Europeans, and the importance of their place in Central Otago's history has often been overlooked.
The railway finally made it as far as Clyde in 1907, with the station's official opening on 2 April 1907 by the prime minister, William Hall-Jones. The Cromwell Railway and Progress League, having been formed in 1906 to influence the extension of the railway through the gorge to Cromwell, set about lobbying the Government with increasing frequency. However, work on the railway line stopped at Clyde until 1914. The lobby group stressed the high cost of transport between Cromwell and Clyde, the impact on the region's farmers and also pointed to the inadequacies of the road:
"Irrigation first", was the Government's reply, reflecting their desire to harness the economic benefits of the Country's nascent agricultural potential. The Government's response was nothing new, having espoused this priority since at least 1899. This would not stop the representations, however.
An announcement to restart the railway extension was made in March 1914, and works were established in the following months with new surveys taking place. The railway started in earnest in September and by the end of 1916 some of rail had been laid. The line to Cromwell was not completed until July 1921 significantly overrunning the predicted two to three years it would take. An E class (Double Fairlie locomotive), Josephine, which pulled all the trains in the gorge during the construction era, is now a museum piece in the Otago Settlers Museum.
Cromwell was the terminus of the Otago Central Railway and consisted of a railway station building, five staff houses, a 6000 gallon locomotive watering tank, stockyards, an engine-shed, turntable coal facilities and the station sidings were able to accommodate nearly 100 wagons. At the time, it was by far the most economic way to get the region's produce to Dunedin and was a boon for the runholders of Waenga Station and the orchardists in the gorge.
With the coming of the Clyde dam, the Cromwell-Clyde railway was closed in 1980. When the dam itself was completed, the line to Clyde had little other traffic and the section from Middlemarch to Clyde was closed on 30 April 1990. The line beyond Middlemarch was lifted during 1991, and the track-bed as far as Clyde was handed over to the Department of Conservation in 1993, becoming the Otago Central Rail Trail.
The Annan's were one of the first families to establish an orchard at the southern end of the gorge on what would become Fruitgrowers Road. In 1901 William Annan cleared his piece of land, built a cob shelter, and planted his fruit trees. Imported from Australia, the first trees Annan planted were a diverse mix to test what would be most suitable for the challenging Central Otago climate and included citrus, almond, walnut, cherry, apricot, apple, pear, peach, nectarine, quince and grape. By 1914 he had a healthy orchard and was mentioned in the Evening Star as part of an exhibition of fruit from Central Otago.
The last orchardist to leave the Cromwell Gorge ahead of inundation by Lake Dunstan, was Kevin Jackson, who had run an orchard in the gorge from 19691989. Jackson and many others whose livelihoods would be irrevocably damaged by the filling of the dam challenged the Government, but to no avail. Only a few trees from what was Jackson's orchard () still remain at the edge the lake.
The reservoir behind the Clyde dam flooded a total of of productive land, including twelve large orchards on the river terraces along both sides of the Cromwell Gorge, five orchards at Lowburn, and fertile farmlands on both sides of the Clutha River in the Lowburn area.
Protests that the dam would flood established orchards, the railway, State Highway 8 as well as parts of Cromwell were all ignored with the high dam becoming part of the National Government's Think Big policy.
Work during the dam's early construction phase in 1982 identified numerous faults and beneath the dam in particular, the River Channel Fault. Despite considerable amounts of concrete being pumped into tunnels across the fault to act as shear pins, the faults posed a significant risk and forced a redesign of the dam leading to the incorporation of a controversial slip joint. The slip joint is designed to accommodate up to of lateral fault movement and of vertical movement. Geologists at the time considered there was a low to very-low possibility of movement along the Dunstan Fault upstream of the dam in the event of a major earthquake; such a movement could lead to up to of relative movement on the River Channel Fault at the dam site.
Unlike the Roxburgh Gorge, where no archaeological survey was ever undertaken before the Roxburgh Dam was built, the Cromwell Gorge would reveal a rich wealth of mining era (1862-1890) and some pre-European sites. In all, 44 rock shelters were recorded in the Cromwell Gorge.
Over the duration of the project, approximately 2000 sites were added to the national site recording scheme with almost every farm in the Upper Clutha being systematically surveyed.
Perhaps the greatest site of interest of the entire ten-year project was the excavation of Cromwell's Chinatown at the confluence of the Clutha and Kawarau Rivers. The site had been abandoned since the 1920s when it was excavated over a 10-week period in 1980, many of the artifacts going on display in the Cromwell Museum.
Ritchie (1989) presented a compilation of 617 sites of archaeological significance, 85 of which were submerged in the Cromwell Gorge due to the filling of Lake Dunstan. A total of 250 sites were lost in the greater Lake Dunstan area due to the filling of the lake.
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On 13 July 2020 a new slip near Cromwell occurred above Deadman's Point Bridge on the true left of Lake Dunstan. The difficulty in accessing the slip resulted in a rather novel remediation technique; helicopters with monsoon buckets were used to sluice loose material and dislodge unstable rock by dropping large quantities of water directly onto the slip. With the establishment of a safe bench to work from, and an abseiling team cleared the remaining loose material over the following days.
One of the Clyde Dam's most vocal critics was Gerald Lensen, a geologist and the former head of Earth Deformation at the DSIR. Lensen had argued on numerous occasions that the Clyde Dam was unsafe, having been built on an active fault zone.
The National Party's Think Big economic policy was heavily criticised and debated during the early stages of the dam construction , and the dam was protested extensively by all those affected by it. Workers unions during the construction of the dam held many strikes.
As the landslide stabilisation of the Cairnmuir Slide neared completion, a protest slogan was painted on the lower portion of the drainage apron which read Hands Off Beaumont referring to the potential of a further dam being built near Beaumont, downstream on the Clutha River. The remnants of this graffiti are still visible.
Wider impacts with the filling of Lake Dustan have continued to impact communities with the spread of lagarosiphon (lake weed), and the continued sedimentation and silting-up of the Kawerau Arm of Lake Dunstan.
Lake Dunstan itself is navigable from the Clyde Dam through the gorge to Cromwell and beyond.
The final section of road through the Cromwell Gorge was opened in 1988.
The realignment of SH8 directly affected twenty nine sites of archaeological significance. The majority of the sites were associated with heritage gold mining activities (stone walled buildings, stone walls, dams, water races, stone stacks), although six sites were pre-historic rock shelters.
Moa finds continued during roadworks; the remains of at least five moas were successfully recovered when a wary bulldozer operator noticed moa bone fragments at the top of his blade while realigning the road section above the old Cromwell Railway site.
The trail through the gorge from Clyde to Cromwell's Historical Precinct is , although the trail currently extends a further north of Cromwell along the western shore of Lake Dunstan.
Despite a lack of recent movement near the Clyde Dam, the recurrence interval for the Dunstan Fault is estimated to be ~7000 years
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