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Central Otago’s terrain and sub-regions
With its vines and wineries spread over an area four times larger than the Hawke’s Bay wine region and about twice as large as that of Marlborough, Central Otago is the most dispersed of New Zealand’s wine regions. Yet Central’s area in vines is about one third that of Hawke’s Bay and about 7 per cent that of Marlborough. Vines in Central Otago are clustered in what the local winegrowers call sub-regions, some of which are over 100 kilometres apart. Each sub-region has its own distinctive history, style, character and contribution to the story of the evolution of winegrowing here. As the wineries gradually acquire land in several sub-regions, their local distinctiveness erodes, although the quality of their wine may improve as they discover better sites for growing Pinot Noir. The six sub-regions commonly identified are: Wanaka; Gibbston and the Kawarau Valley; Luggate to Cromwell ; Tarras to Cromwell, including Bendigo ; Bannockburn; and Alexandra.
The terrain of Central Otago is aptly described as ‘basin and range’; valleys of varied widths are separated by substantial mountain ranges. The Clutha and Kawarau rivers and their tributaries provide the network to relate this terrain to the distribution of the region’s vineyards and wineries. The Clutha sets the north-south trend. From its source at Lake Wanaka it flows southeast for 20 kilometres before being joined by the
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Lindis River just before the first arm of the triangular Loop Road leading to the former mining town of Bendigo. The Clutha then carves south, the Pisa Range to its west and the Dunstan Mountains to its east. After the Kawarau River joins it at Cromwell the Clutha continues slightly east of south to Alexandra, the northern ridge of the Garvie Mountains to its west.
The Kawarau River has its source in Lake Wakatipu from where it sweeps eastwards around the northern fringe of the Remarkables, skirting the triangular tip of the Carrick Range before continuing eastwards to join the Clutha at Cromwell. This complex terrain, sculpted by these two rivers and their tributaries, results in slopes with many different aspects, parts of valleys that are shaded even during summer, and steeper slopes that in other countries are planted in vines but in Central Otago still grow tussock.
One way of revealing the relationships between vines and their terrain is to predict location of vineyards by using measurements of the terrain that also strongly influence the weather and climate of the region. Three criteria are used in the digital terrain model that follows: elevation, slope, and aspect. Elevation has a direct effect on temperature. The decline in temperature with height is about 1°C per 100 metres of elevation. The difference in elevation along the valley of the Clutha is small and the differences in temperature subdued. Between Lake Wanaka and Alexandra the change in elevation is only 100 metres. As a result the difference in temperature between the two locations directly attributable to elevation is about 1°C, although many other influences, notably aspect, affect the climates of individual sites.
In contrast, changes in temperature as a result of elevation are spectacular over short distances between valleys of the Clutha and Kawarau and the adjacent hills and mountains. Differences in elevation of 500 to 1000 metres between the floor of a valley and the nearest major ridge are common. As a result, daytime temperature differences of between 5°C and 10°C over a few kilometres are also common. Elevation has a major influence on precipitation and wind. Being in the rain shadow of the Southern Alps, most of Central Otago receives under 600 millimetres of precipitation annually. Irrigation is essential here. Gordon Cossens work also established that in terrain such as that of Central Otago the lapse rate varies from between 0.3°C to the widely quoted 1°C.
Slope also influences the potential for winegrowing. Slopes of over 15 degrees make mechanical cultivation difficult. Central Otago’s western hills and mountains are much steeper than those further east. The Remarkables, and further north the Crown Range and mountains west of the Cardrona River, have very few slopes less than 15 degrees.
