|Definition:||A man-made underground channel for transporting water from higher to lower areas|
Qanat is a traditional way of supplying water in hot and arid climates within limited distance of a mountain range. Developed some 3000 years ago, it still serves thousands of people worldwide. It originates from Iran or Oman and is most widespread across South-Western Asia, from Mediterranean to Himalaya with a presence in North Africa and south-eastern arabic peninsula.
It consists of an underground gallery that drains water from the aquifer at first (collection section) and then channels it (transport section) along a gentle 1/1000 slope, with a series of vertical shafts which are artifacts of the building process but also serve for ventilation and service access, with an opening of the channel section as it reaches the groundlevel and a a further open air canal.
You may read more about it in a great article at Wikipedia.
Despite the widespread use of pipelines and pumps, qanats still provide water for many people. It is a sustainable and enviromentally-friendly way of using water from natural resources.
Qanats are underground structures, vulnerable to unplanned ground works. Mapping them could hopefully save some of them from destruction.
Afghanistan is probably the country most dependent on qanat network, however after decades of wars large part of it lay in rubble. Having tools for mapping qanat could help rebuilding them in the future, when (hopefully!) the situation improves there,
Despite being mostly underground structures, qanats are quite easily traceable from satellite photos and surface surveys, due to the openings of vertical shafts.
The proposals for tagging qanats are:
- Mark the way with man_made=qanat and shafts with qanat=shaft. This, however, will not be rendered by any existing engine.
- Mark the way with waterway=canal + canal=qanat + tunnel=yes. It leaves possibility to mark parts of qanat which are not underground (sometimes happens in the end sections) and gives chance to be rendered by existing engines. Still the question is how to tag shafts.
- Mark the way with waterway=aqueduct + aqueduct=qanat. This implies also introduction of aqueduct=surface and aqueduct=bridge for surface and Roman-style aqueducts.
An example of mapped and unmapped qanats. East of town Mastung in Pakistan, south of Qetta.
The qanat itself doesn't have to be rendered on a default map, as it is an underground structure. The shafts, however, could be marked, as they are large and observable terrain features.