Under the last Shah, the great feudal estates were broken up and the land returned to the labourers.
This meant that no single person was responsible for the maintenance of the Qanat, and accordingly these fell into serious disrepair and the tunnels became blocked. More recently the system of religious endowment, or vaqf, under which much land is managed by tenants of the religious authorities has also led to a decline in long term maintenance. The Diagram above shows more detail on the Qanat system and the way in which the drain-off from the moutain is trapped by a layer of impervious rock to create a water table. Vertical shafts are constructed to dig the tunnel and for the removal of earth. The shafts are subsequently used for maintenance.