The Turpan water system, also called the Turfan kārēz system, is used for

water supply Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. Th ...

via a vertical tunnel in the Turpan Depression of

Xinjiang Xinjiang,; , SASM/GNC romanization, SASM/GNC: Chinese postal romanization, previously romanized as Sinkiang, officially the Xinjiang Uygur Autonomous Region (XUAR), is an Autonomous regions of China, autonomous region of the China, People' ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. "Karez" () is a word in the local

Uyghur language Uyghur or Uighur (; , , or , , ), formerly known as Turki or Eastern Turki, is a Turkic languages, Turkic language with 8 to 13 million speakers (), spoken primarily by the Uyghur people in the Xinjiang Uyghur Autonomous Region of Western ...

that is derived from the word in the

Persian language Persian ( ), also known by its endonym and exonym, endonym Farsi (, Fārsī ), is a Western Iranian languages, Western Iranian language belonging to the Iranian languages, Iranian branch of the Indo-Iranian languages, Indo-Iranian subdivision ...

for the system from which it is derived: the 3000-year-old qanāt. Turpan has the Turpan Karez Paradise (a Protected Area of the People's Republic of China), which is dedicated to demonstrating its karez water system, as well as exhibiting other historical artifacts. Turpan's karez well system was crucial in Turpan's development as an important oasis stopover on the

Silk Road The Silk Road was a network of Asian trade routes active from the second century BCE until the mid-15th century. Spanning over , it played a central role in facilitating economic, cultural, political, and religious interactions between the ...

, which skirted the barren and hostile

Taklamakan Desert The Taklamakan Desert ( ) is a desert in northwest China's Xinjiang region. Located inside the Tarim Basin in Southern Xinjiang, it is bounded by the Kunlun Mountains to the south, the Pamir Mountains to the west, the Tian Shan range to the ...

Description

Turpan's karez water system is made up of a horizontal series of vertically dug

well A well is an excavation or structure created on the earth by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The ...

s that are then linked by underground water

canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...

s to collect water from the watershed

surface runoff Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other ...

from the base of the Tian Shan Mountains and the nearby Flaming Mountains. The canals channel the water to the surface, taking advantage of the current provided by the

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

of the downward

slope In mathematics, the slope or gradient of a Line (mathematics), line is a number that describes the direction (geometry), direction of the line on a plane (geometry), plane. Often denoted by the letter ''m'', slope is calculated as the ratio of t ...

of the Turpan Depression. The canals are mostly underground to reduce water

evaporation Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...

and to make the slope long enough to reach far distances being only gravity fed. The system has wells, dams and underground canals built to store the water and control the amount of water flow. Vertical wells are dug at various points to tap into the

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

flowing down sloping land from the source, the mountain runoff. The water is then channeled through underground canals dug from the bottom of one well to the next well and then to the desired destination. Turpan's karez

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

system of special connected wells is believed to be of indigenous origin in China, perhaps combined with technology arriving from more western regions. In

, the greatest number of karez wells are in the Turpan Depression, where today there remain over 1100 karez wells and channels having a total length of over . The local geography makes karez wells practical for agricultural irrigation and other uses. Turpan is located in the second deepest geographical depression in the world, with over of land below

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

and with soil that forms a sturdy basin. Water naturally flows down from the nearby mountains during the rainy season in an underground current to the low depression basin under the desert. The Turpan summer is very hot and dry with periods of wind and blowing sand.

Importance

Ample water was crucial to Turpan, so that the oasis city could service the many caravans on the Silk Route resting there near a route skirting the

. The caravans included merchant traders and

missionaries A missionary is a member of a religious group who is sent into an area in order to promote its faith or provide services to people, such as education, literacy, social justice, health care, and economic development.Thomas Hale 'On Being a Miss ...

with their armed escorts, animals including camels, sometimes numbering into the thousands, along with camel drivers, agents and other personnel, all of whom might stay for a week or more. The caravans needed pastures for their animals, resting facilities, trading

bazaar A bazaar or souk is a marketplace consisting of multiple small Market stall, stalls or shops, especially in the Middle East, the Balkans, Central Asia, North Africa and South Asia. They are traditionally located in vaulted or covered streets th ...

s for conducting business and replenishment of food and water.

Potential UNESCO World Heritage Site

Karez wells in the Turfan area are on the UNESCO World Heritage Sites Tentative List for China.

Threatened by global warming

There are 20,000 glaciers in Xinjiang – nearly half of all the glaciers in China. The water from the glaciers via the underground channels has provided a stable water source year round, independent of season, for thousands of years. But since the 1950s, Xinjiang's glaciers have retreated by between 21 percent to 27 percent due to

global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

, threatening the agricultural productivity of the region.

References

External links