The Turpan depression is an unlikely garden. The land drops to 154 metres below sea level — the second-lowest exposed ground on earth — and the summer heat is legendary: ground temperatures high enough to be named the Flaming Mountains. Annual rainfall is around sixteen millimetres. And yet the county has grown grapes and melons for some two thousand years, and its raisins feed markets across China.
A basin that burns
The water exists — the Bogda range to the north holds years of snow — but every surface channel loses most of its flow to evaporation long before it reaches the fields. The solution, arrived at independently across the arid belt from Persia to China, was to move the river underground. In Persia the structure is called a qanat; in Xinjiang, karez.
How the karez works
A karez is a gently sloping tunnel, dug from the fields back up toward the mountains, tapped below the water table so that groundwater percolates in and runs down by gravity alone. Vertical shafts — sometimes hundreds per channel — provide digging access and, later, maintenance. At the surface end the water finally emerges into open channels and the oasis. No pumps, no evaporation under the tunnel roof, and a flow that self-regulates with the seasons. Turpan’s system grew to over a thousand channels; their combined galleries are credited at thousands of kilometres — a civil works comparable to the Great Wall in scale, if invisible from it.
What the water fed
Concentrate irrigation like that made Turpan an anomaly: an agricultural power in a desert, wealthy enough to be a silk road node, cosmopolitan enough that its dead cities — Jiaohe and Gaochang — hosted Buddhist, Manichaean and Nestorian communities at once. The oasis’s famous products all ride on the karez: the table grapes, the seedless raisins dried in air-vented brick drying houses, the honeydew melons of neighbouring Hami’s reputation. When the water system works, the desert blooms; when a channel silts and is not maintained, a village dies. The ruins of the Tarim rim are, at bottom, a record of water won and water lost.
Visiting a working channel
The museum channels near Turpan city let you walk down the shaft stairs and stand beside the running gallery — cold air, the sound of water in the dark, an engineering lesson you feel on your skin. Better still, our Xinjiang oases journey visits a still-working village channel with the families who maintain it, then follows the water’s logic out to the vineyards and the dead cities it fed. The Xinjiang guide covers the region’s wider geography.
Where this leads
The Xinjiang oases journey
Xinjiang guide
The oasis kitchens