qanāt, ancient type of water-supply system, developed and still used in arid regions of the world. A qanāt taps underground mountain water sources trapped in and beneath the upper reaches of alluvial fans and channels the water downhill through a series of gently sloping tunnels, often several kilometres long, to the places where it is needed for irrigation and domestic use. The development of qanāts probably began about 2,500 or 3,000 years ago in Iran, and the technology spread eastward to Afghanistan and westward to Egypt. Although new qanāts are seldom built today, many old qanāts are still used in Iran and Afghanistan, chiefly for irrigation.