Underground 'Great Wall' ensures water supply in arid Turpan

The Great Wall stretches across northern China from Hushan in Shandong Province to Jiayuguan in Gansu Province. In northwestern China's Xinjiang, there is an underground "Great Wall" known as a karez, a vast subterranean irrigation system that surrounds the city of Turpan.

Due to its extremely hot and dry climate, Turpan experiences an annual evaporation rate of 3,000 millimeters and an annual precipitation of just 16 millimeters. Collecting rainwater, preventing evaporation, and transporting it to fields and families has always been a key issue in the region. Around 2,000 years ago, an underground irrigation system known as a "karez" was created. Ancient engineers exploited the sloping terrain between the Tianshan Mountains and the Turpan Basin to collect melted snow and transport it via underground channels to prevent evaporation and absorption in the sand.

This network of channels extends for over 5,000 kilometers from Turpan, a distance that equals the journey between Beijing and Urumqi. Currently, 238 of these channels remain in use.

The Karez System Cultural Landscape was inscribed as a UNESCO World Heritage Site in 2014.