Sichuan
Sichuan Geography & Climate
Geography
Sichuan is two entirely different places: a lowland basin in the east and high plateau and mountains in the west, divided by a sharp line.
The Red Basin
The Sichuan Basin is a broad lowland of red sandstone at around 250 to 700 metres, enclosed on every side by mountains. It is intensely fertile and intensively farmed, and it supports one of the densest rural populations on earth — the province has around eighty million people and the basin holds most of them. The enclosure also traps air, which is why the basin is famously overcast.
The western mountains
West of the basin the land rises abruptly onto the eastern edge of the Tibetan plateau, and within a couple of hundred kilometres reaches above 7,500 metres at Gongga Shan. This is the Hengduan range, running north to south and cut by deep parallel gorges — the Yangtze, Mekong and Salween all run through this system within a hundred kilometres of each other.
Biodiversity
The altitude range and the gorges make this one of the most biologically diverse temperate regions on earth, and it is the last refuge of the giant panda, whose remaining habitat is almost entirely in these mountains.
Earthquakes
The plateau margin is a major fault system. The 2008 Wenchuan earthquake killed around 87,000 people, and the 2017 Jiuzhaigou quake damaged the park.
Three rivers, one hundred kilometres
In the Hengduan mountains on Sichuan’s western edge, the upper Yangtze, Mekong and Salween run parallel in gorges within about a hundred kilometres of one another before diverging to reach the sea thousands of kilometres apart — in the East China Sea, southern Vietnam and Myanmar respectively. The Three Parallel Rivers area is UNESCO-listed and is among the most biologically rich temperate regions on earth for exactly that compression of habitats.
Travertine
Mineral-rich water at Jiuzhaigou and Huanglong deposits calcium carbonate, building terraced pools of intense colour.
Climate Patterns
The Sichuan basin has one of the most distinctive climates in China, and the defining feature is the absence of sun.
The overcast basin
Enclosed by mountains on every side, the basin traps humid air and cloud. Chengdu receives among the fewest hours of sunshine of any major city in China — fewer than a thousand a year in some reckonings, comparable to the gloomiest parts of northern Europe. There is a Sichuanese saying that the dogs bark when the sun comes out, because they are not used to it. Winter in particular is a long grey damp.
Summer
June to August is hot and very humid, 28 to 34°C with little breeze, and the basin’s enclosure makes it feel worse. This is also the rainy season, with most of the year’s precipitation and frequent landslides on the mountain roads.
Winter
December to February is mild by northern Chinese standards — 5 to 10°C — but damp, grey and cold indoors, since the basin lies south of the line where central heating was historically provided.
The west
Entirely different. The plateau above 3,000 metres is cold, dry and brilliantly sunny, with strong UV, freezing nights most of the year, and passes that close for snow. The transition from basin to plateau takes a few hours by road.
Mist and the food
The damp is usually offered as the explanation for the cuisine. The traditional argument is that chilli and Sichuan pepper drive out the internal damp that the basin’s climate produces — a piece of Chinese medical reasoning that Sichuanese still cite and that at least explains why a cuisine this fierce developed somewhere this cool and grey rather than somewhere hot.
Autumn colour
Mid-October to early November in the northern mountains, which is when Jiuzhaigou is at its most photographed.