坎兒井由豎井、暗渠、明渠、澇壩四部份組成。
從天山溶雪引發的潛流上游開始，每隔20公尺挖一豎井，一直挖到下游低處，挖出水面，並由井底的暗渠將豎井連接起來，引上地面灌溉、使用，
全由當地農民憑雙手及簡單工具，打井挖渠，被後人譽為中國古代三大工程之一。

吐魯番的坎兒井有近千條，總長約5000公里，如人體血脈分佈在盆地四處，成為綠洲的生命之泉。

更有意思的是，坎兒井剛好分佈在當年的絲綢之路上，包括伊朗、土庫曼斯坦和中國的新疆、甘肅、陝西等地，
幾乎可以肯定，它與絲路的昌盛有不可分隔的關係。


The Karez is an underground irrigation system that was constructed over 2,000 years ago and
is considered one of the greatest engineering achievements of ancient China,
with the Great Wall and the Grand Canal.

It is a series of wells and underground channels that transferred water,
usually from the glaciers on the base of the Tianshan,to communities in the area.

Many cities on the ancient Silk Road, some as far west as modern Iran,
relied on this irrigation system as a primary supply of water.