Port: Geography and climate

Pombal’s demarcation, modified a number of times since 1756 (see douro), corresponds closely to an area of pre-Cambrian schist surrounded by granite. From the village of Barqueiros about 70 km/40 miles upstream from Oporto, the region fans out either side of the river stretching as far as the frontier with Spain. It is referred to by the port shippers as ‘the Douro’, or by those in charge of the UNESCO World Heritage sites as Alto Douro Wine Country. The vineyards are shielded from the influence of the Atlantic by the Serra do Marão, a range of mountains rising to an elevation of 1,400 m/4,600 ft. Inland, the climate becomes progressively more extreme. Annual rainfall, which averages 1,200 mm/47 in on the coast, rises to over 1,500 mm on the mountains and then diminishes sharply, falling to as little as 400 mm at Barca d’Alva on the Spanish border. Summer temperatures in the vineyards frequently exceed 35 °C/95 °F. It is hard to imagine a more inhospitable place to grow grapes. The topsoils in this mountainous region of Portugal are shallow, stony, and low in nutrients. Over a period of 300 years, however, the land has been worked to great advantage. The valley sides are very steep but terraces hacked from the schist, often with little more than a shovel and crowbar support, give vines a metre or two of soil in which to establish a root system. The bedrock fractures vertically, however, and, once established, vines root deeply in search of water and nutrients.