Cuyo (Central Andes)
Cuyo (Central Andes) Geography & Climate
Geography
Cuyo sits in the rain shadow of the Andes at their highest, and it is fundamentally a desert with rivers running through it.
Aconcagua and the high Andes
The Andes reach their greatest height here: Aconcagua at 6,961 metres is the highest mountain outside Asia and the highest in both the Southern and Western hemispheres. Around it a cluster of peaks exceed 6,000 metres, and the range is broad and arid rather than glaciated in the Patagonian way.
Rivers from snow
Almost no rain falls on the valleys — Mendoza gets around 200 millimetres a year — so everything depends on snowmelt. The Mendoza, Tunuyan, San Juan River and Atuel rivers carry water down from the range and into irrigation systems that support the vineyards, the orchards and the cities. The oases are sharply bounded: vineyard on one side of a road, bare desert on the other.
The Uco valley
A high basin at 900 to 1,500 metres where cold air drains off the mountains at night, giving a very wide day-to-night temperature range that suits wine.
Ischigualasto and Talampaya
A desert basin of eroded sandstone and clay exposing a continuous sequence of Triassic rock, from which some of the earliest dinosaurs known — Eoraptor and Herrerasaurus — have been excavated. UNESCO-listed for exactly that.
The Uspallata corridor
The valley carrying the road to Chile is the only practical crossing of the high Andes for hundreds of kilometres, and it has been the route for everything — the Inca road, the colonial mule trains, San Martin’s army in 1817, the transandine railway whose ruined viaducts still stand beside the highway, and now the lorries queueing at the border. The natural bridge at Puente del Inca, stained orange by mineral springs, sits alongside it.
Earthquakes
The subduction zone runs immediately west; Mendoza and San Juan Province have both been levelled in historic times.
Climate Patterns
Cuyo has a continental desert climate, and its two defining features are dryness and the daily temperature range.
Rain, or the lack of it
Mendoza receives around 200 millimetres a year, San Juan Province less. This is genuine desert, and the green is entirely irrigated. Summer brings occasional violent thunderstorms with hail, which is the winegrower’s nightmare — a single storm can destroy a season’s crop, and the vineyards are increasingly netted against it.
Summer and winter
December to February reaches 32 to 36°C by day and drops to around 18 at night. June to August is 14 to 17°C by day and near freezing after dark, with brilliant clear skies and snow on the range.
The day-to-night swing
Cold air draining off the Andes at night gives a range of fifteen degrees or more, particularly in the Uco valley. This is precisely what makes the wine: warm days ripen the fruit while cold nights preserve acidity and colour.
The zonda
A downslope wind that arrives from the west after crossing the Andes, dropping its moisture on the Chilean side and arriving hot, dry and laden with dust. It can raise the temperature by fifteen degrees in an hour, gust over 100 km/h, and is blamed locally for headaches and bad temper. Schools sometimes close for it.
Why the desert suits wine
The combination is unusual and it is the region’s whole advantage. Low humidity means almost no fungal disease, so vines can be grown with very little spraying and organic viticulture is straightforward. Irrigation from snowmelt means water is applied when the grower chooses rather than when it rains. And the altitude gives intense sunlight with cold nights. It is close to a laboratory for growing grapes, and that is why the industry sits here.
Altitude
Aconcagua’s summit is arctic in any season.