Qanats: Rivers That Flow Underground
In the dry lands of Iran and nearby countries, rain is scarce and the summer sun is fierce. Water that sits in an open ditch soon vanishes into the air. Thousands of years ago, farmers in this region found a clever way to bring water to their fields. The invention is called the qanat.
A qanat is a long, gently sloping tunnel dug by hand. Builders began at the foot of a mountain, where rain and snowmelt soak into the ground and collect below the surface. From there they dug a tunnel that sloped a little less steeply than the land above it. The water ran downhill through the tunnel until it came out into the open, sometimes many miles away, beside a village. No pumps were needed, because gravity did all of the work.
Digging a qanat took skilled crews. At regular spaces along the route, they also dug vertical shafts. Workers hauled the soil up through the shafts, and the openings let in fresh air and helped the crew keep the tunnel pointed in the right direction. Later, the shafts gave people a way to climb down and make repairs.
Because the water traveled underground, very little of it evaporated in the heat. A well-kept qanat could deliver a steady flow all year long. Some qanats are still in use, giving water to farms and villages today.