I promised about 10 days ago to start a topic on qanats over here on the health/welfare/water circle.so here it is.
"A Qanāt or karez/kariz (Persian: قنات/کاریز) is a gently sloping underground channel to transport water from an aquifer or water well to surface for irrigation and drinking. Qanat is an old system of water supply from a deep well with a series of vertical access shafts, Qanāts still create a reliable supply of water for human settlements and irrigation in hot, arid, and semi-arid climates. The qanat technology is known to have been developed in Iran by the Persian people sometime in the early 1st millennium BC, and spread from there slowly westward and eastward"
And here's the embiggened version of the qanat cross section. I admit I have a hard time grokking this.
There's also a link to qanats in the Americas, though there is some question about whether Puquios were an indigenous development or brought by colonists.