Qanats

Background

In the early part of the first millennium B.C., Persians started constructing elaborate tunnel systems called

qanats

for extracting groundwater in the dry mountain basins of present-day Iran (see figure 1).

Qanat

tunnels were

hand-dug, just large enough to fit the person doing the digging. Along the length of a qanat, which can be

several kilometers, vertical shafts were sunk at intervals of 20 to 30 meters to remove excavated material and

to provide ventilation and access for repairs. The main qanat tunnel sloped gently down from pre-mountainous

alluvial fans to an outlet at a village. From there, canals would distribute water to fields for irrigation. These

amazing structures allowed Persian farmers to succeed despite long dry periods when there was no surface

water to be had. Many

qanats

are still in use stretching from China on the east to Morocco on the west, and even

to the Americas.