Kariz Irrigation System
Kariz (also known as kareze or qanat) is an ancient underground channel irrigation system invented in Persia (Iran). It is a sloping tunnel that brings water from an underground source in a range of hills down to a dry plain at the foot of these hills. Its advantage over an openair aqueduct is that less water is lost by evaporation on its way from the hill to the plain.
In 714 BCE, when Sargon II invaded Armenia, he saw an irrigation system not yet known in Bet-Nahrain, called by its Arabic name qanat or the Farsi kariz. He brought the secret back to Assyria. Qanat irrigation was then spread over the Near East, as far as North Africa, and is still used.
In Tajikistan, as early as the fourth to fifth centuries BCE, a canal was constructed in the Vakhsh River Valley, near present-day Qurghonteppa (Kurgan-Tyube), which irrigated fifty square kilometers of land. Subterranean canals and reservoirs, with containers made of copper (known as kariz), were extensively constructed in the northern parts of Tajikistan in the ninth and tenth centuries CE. These kariz carried copious supplies of fresh water from the mountains to waterless plots of land, often many kilometers away. Sometimes as deep as forty meters, they were constructed underground to prevent evaporation of water as it crossed the sun-baked steppe. They were carefully engineered to bring the water to the surface at just the point it was required so that pumping was unnecessary.
In Turpan and Hami Prefectures of China's Xinjiang Uygur Autonomous Region, kariz comprising wells connected by underground channels were known as one of the three ancient projects in China, along with the Great Wall and the (Beijing-Hangzhou) Grand Canal. Although there is plenty of rainfall on the slopes of the Tengri-Tagh Mountains, the Turpan Basin is extremely dry and blazingly hot in the summer. Taking advantage of the natural incline of the land and the rich underground water source, the people of Turpan created a unique irrigation system. During the golden age of kariz development, 1,700 kariz covering a length of 4,400 kilometers were constructed in Turpan Prefecture. At present, kariz are facing dropping water levels and drying. Experts are worried about the future of kariz, the symbol of Chinese water culture.
In the high and dry plains of Afghanistan, agriculture is often impossible without irrigation. The Afghans have put in place a system for harnessing the water: the kareze tunnels.
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