An open canal for carrying irrigation under controlled conditions through a desert.

A qanat or kariz is a gently sloping underground channel to transport water from an aquifer or water well to the surface for irrigation and drinking, acting as an underground aqueduct. Constructed in Iran, Iraq and numerous other societies, this is an ancient system of water supply from a deep well, that makes use of a series of vertical access shafts. The qanats still create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates, but the value of this system is directly related to the quality, volume, and regularity of the water flow. Traditionally qanats have been built by hand labor in Arab-speaking areas by a group of skilled laborers, known as muqannīs. The profession historically paid well and was typically handed down from father to son.

According to most sources, qanat technology was developed in ancient Iran by the Persian people sometime in the early 1st millennium BCE, and spread from there slowly westward and eastward. However, some other sources suggest a Southeast Arabian origin. In addition, analogous systems appeared to be developed independently in China and South America, specifically, southern Peru.