CH III / D.O RIBERA DEL DUERO HISTORY
Geographical and climatic
context of the Ribera del Duero
Ribera del Duero is a winemaking region spread between the provinces of Soria, Burgos, Segovia and Valladolid. It takes the form of a narrow strip on either side of the River Duero, 110 km long and between 20 and 30 wide. This land coincides with the valley created by the flow of the Duero over the calcareous flood plains.
The Ribera del Duero does not stretch the entire length of the Duero Valley, but rather certain sections which, thanks either to comparative advantages or singular moments in history, have been able to create a terror of vines and fine wines of international renown.
The Ribera del Duero corresponds to the easternmost section of the Valley, a district which has been known as La Ribera for centuries. It is a depression excavated by the Duero and its network of tributaries on a surface of heathland with a maximum altitude of around 900 metres in the west and 1,000 in the east, set in the valley between 150 and 200 metres below.
After the approval of DO Rueda in 1980 and that of La Ribera in 1982, new ones sprang up and were approved for Toro (1987), Cigales (1991), Los Arribes (2007) and the Tierra del Vino de Zamora (2007), all in the Duero Valley, to which others from within and outside the basin were added. This all meant the Duero was becoming consolidated as a land of vines and fine quality wines recognised from the plains of Soria to the river’s estuary in Oporto.
The eastern riverbank lands of the Duero possess unique ecological features. They are at a considerable altitude, which reduces the plants’ growing cycle due to the cold, scarce rainfall, high exposure to the sun and the silica properties found in a lot of the soils, which are well-suited to growing vines. It is a strip of high, flat lands, spread over three levels of platform: the plains, the terraces and small landings in between, and the heaths which interlock with the valley via the slopes. The former were always used for irrigated crops, the second for vines alternating with cereal crops, and the third, those of the hillsides and the ploughed fields.
The vines grew outside the plains, on the gravel terraces left by the river, or on the sandstone platforms, which appear when the overlying sediment is broken down and eroded, or on clay strata reduced to hillocks by erosion.
In all the cases it seems a matter of scraps of horizontal layers, with a sand and gravel composition, secondarily clay, from warm soils, poor for growing cereal crops, suitable for growing little other than grape vines, which dig their long roots deep between these layers, passing through them to obtain water and nutrients at depths which grass crops cannot reach.
«At the foot of the slopes, as a result of the intense general deforestation, there is a build-up of banks of alluvium of clay and loam, with more or less carbonate content, sometimes with good proportions of organic matter, which bring the plots of vines growing at the foot of the slopes extraordinary properties in which it is also not rare to find replanted vines, due to the sharp slopes favouring filtration and run-off of the water, which improves and diversifies the grape’s sensory qualities».
(Molinero, F., 1997: 23)
The climate of La Ribera is a typical high-altitude Mediterranean climate. It is Mediterranean because the planetary position of La Ribera corresponds to the middle subtropical latitudes, under the domination of the Mediterranean influence (42 ºN), in the SW of the European continent. The climate is characterised by the dry summers, an almost total absence of rainfall between mid June and mid September, a circumstance which provides prolonged exposure to the sun and excellent ripening of the grapes. But this also a high altitude climate with big temperature breaks between day and night which favours an accumulation of sugars in the berries, bringing alcoholic strength, smoothness and high fixed acidity, allowing a combination of the most outstanding qualities of the Atlantic and Mediterranean vineyards.
Finally, as it is a high altitude Mediterranean climate, which affects one sector of a closed basin, enclosed by mountains, away from the maritime influences and with very little rainfall, between 450 and 500 mm per year, which makes high yields difficult and favours the excellent ripening and sensory qualities of the fruit, especially the tempranillo, the indigenous grape adapted to these climate conditions. The vine plant has to ration the water and nutrients between only 1 to 3 kilos of grapes, which undoubtedly raises the quality.
The temperature of the Ribera oscillates around an annual mean of 12 ºC, higher towards the west and decreasing as you move further east, due to the altitude. This annual mean temperature ranges from 21 ºC in the month of July to 3.5 ºC in January, but in May, when the vine begins to shoot, averages reach between 13º and 14ºC, rising to 18º in June and 21º in July, before then falling to 12ºC in October, although at the start of this month, when the grapes are harvested, it is above this average temperature. Over the middle six months of the year there are 182 days of “active” temperatures, with 2,300 to 2,800 sunshine hours and 130 frost-free days, conditions which ensure excellent ripening of the grapes.
Moderate temperatures and rainfall do not exclude heat and water stress, which are countered by using modern techniques. The greatest risks to the vineyards of the Ribera can occur in the month of May, as bud burst, which is around the beginning of the month, before if the spring warmth comes early, can seriously damage the meristems of the shoots and mean that the clusters do not form. In effect, although the risk of late frosts, according to Huetz, is 10%, once every ten years, if this phenomenon occurs in May it can wreak insurmountable damage for the harvest, although not for the vine plant. Growers take precautions by generous pruning, so that if the high buds freeze, the frost does not usually affect the lower ones.
At the other extreme you have the arid summers, which have been preceded by dry springs, and which are tackled by drip watering once or twice, safeguarding the harvest and even improving the plants’ metabolic balance. Almost all modern-day plantations are trained along trellises, accompanied by pumps and drip watering systems, which are only used when needed, with no more than around 30 l/m2 per watering.
«Los paisajes vitivinícolas triunfantes de la Ribera del Duero»
– with information from Fernando Molinero and Cayetano Cascos –