In the early part of the first millennium B.C., Persians started constructing elaborate tunnel systems called
for extracting groundwater in the dry mountain basins of present-day Iran (see figure 1).
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
are still in use stretching from China on the east to Morocco on the west, and even
to the Americas.