Hunter's Wines, Marlborough. Hunter's Wines that attract international winegrowers and consumers? Even the viticulturists and winemakers, those closest to the daily and seasonal development of the vine and wine, as well as the scientists, find that question difficult to answer. This chapter explores the application of human effort in Marlborough’s natural environments to tease out the complex interactions between the two. The Wairau andAwatere valleys.
On a clear day when your plane lands at Wellington airport from Christchurch or Auckland it is easy to imagine that the North and South Islands were joined as recently as two million years ago.
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They overlap. Picton and Nelson are at the same latitude as Wellington, while Motueka is north of Martinborough, and Cape Palliser, the southernmost tip of the North Island, is well south of Blenheim. Because the rugged southern tip of the North Island protrudes so far south it provides some shelter to the Wairau Valley from easterly weather conditions (Figure 7. 1). Even more importantly, the Richmond Range protects the Wairau Valley from the north and west, and the Inland and Seaward Kaikouras protect it from the south. Weather systems from the west also often funnel through Cook Strait, so it is not surprising that the Wairau Valley has low precipitation compared with most of New Zealand and that most years Blenheim vies with Nelson for the highest annual sunshine hours. Their location gives the valleys of the Wairau and Awatere distinctive atmospheric environments for the vine.
The Wairau River has its headwaters in the Spenser Mountains and St Arnaud Range. When you cross from St Arnaud at the base of the Rainbow Springs ski field into the headwaters of the Wairau River the origins of the downstream plains become obvious. The tumbling mountain streams surging across tussock pastures have names like Stony Creek and the Wash. They are charged with smooth, flat and rounded pebbles and boulders that strew the already braided beds and fill the narrow valley. On its course to the sea at Cloudy Bay the Wairau flows only slightly north of east, hugging the Richmond Range that separates Blenheim from Nelson. On its northern bank the flood plain is narrow and the tributaries are short. This is one fork of the Alpine Fault that reappears in the North Island.
When the Waihopai joins the Wairau from the south, about 10 kilometres west of Renwick and 30 kilometres from the east coast of Cloudy Bay, the valley widens. These southern rivers – the Waihopai, the Omaka with its tributaries Mill Stream and the Fairhall River, together with the Taylor River, that gathers in several streams before joining the Opawa – are much longer than those on the north bank. They have formed a series of almost flat valleys subsidiary to the Wairau, face north and are separated by low ridges rising to between 100 and 200 metres. These ridges have mainly clay soils, often overlain by loess. The valleys between them are a very complex mix of silts, gravels and clay with clay-loam soils. On the terrain of these valleys and the flattish plain between them and the Wairau River, an intensification of land use has been played out. It is as dramatic as has occurred at any time, anywhere in New Zealand. During the last four decades the species Vitis vinifera has taken over this Wairau Plain as well as the terraces and rolling hills flanking the Awatere River to the south.
The pattern of streams and rivers of the Wairau Plain, and especially of the Southern Valleys, gives clues to their origins and the soils that have formed here (Figure 7.2). Today smaller watercourses wander across the flat valleys and plain as if not quite knowing in which direction to flow. Without artificial drainage their courses would be even more complicated. Their current pattern is just one instant in a long history of changing sea level, periods of glaciation and glacial melt, and changes in the types of rocks being eroded in the headwaters of rivers and transported during many sequences of deposition and erosion. Rivers and streams have changed course; parts of the plains have been lakes when fine sediments have been deposited and later exposed. The presence of loess – materials fine enough to be blown by wind then deposited -makes the range of parent materials and their presence in the current soils even more complicated. It is not surprising that these soils and their deeper surface stratigraphy change rapidly even over small distances.
As recently as 1863 the whole of the Wairau flood plain was covered in floodwater. When the Wairau and Waihopai are in full spring flood, more than 5000 cubic metres of water per second rush past Conders Bend. Before the flood-control works of the 1960s.