The use of qanats for carrying the underground water dates back to 3000 years ago in Ancient Persia. This technique firstly was practiced by Parthian and Mades, and then was stretched across the other parts of the world. The aim of digging qanat was to provide a settlement, a sustained community, agricultural development, and flourishing economy, no matter who have dug it. According to a theory, the gradual transformation of water tunnels caused qanats to come into existence. Another theory still emphasizes that change in climatic conditions and decrease of water supplies is the reasons of qanats coming into being. However, both theories are open to discussion.One can trace back the origin of qanats to the ancient Iranian culture. Qanats have been made upon certain conditions including ecological, climatic, hyrogeologic, and topographic situations. As well as, according to a theory, the existence of qanat depends on the existence of a deep underground water supply at the foot of alluvial fan (cone). The structure of a qanat consists of a mother well, wells, channels, and an exit point for water that water comes out of that point & then pours down through a steady slope.
The distribution of primary settlements upon alluvial fan (cone) in the internal plateau of Iran and at the margins of Iran’s deserts is influenced by the distribution patterns of qanat systems and water channels. The uniformity in traditional imitation methods at that time has contributed to the historical development process of villages & altered village’s instances of use. In the course of this process, lands have changed into gardens and houses in the outskirts, and the irrigation systems have altered into roads and passage systems; and then the urban development came into being.In the present article, the author studies the important role of water and topography in the formation of primmy settlements and their road networks. The article also casts a glance at some other influencing factors such as religion, trade, security & political considerations, road, and so on which have played important roles in the formation of these settlements.