2. The Role of Qanat and Irrigation Networks in the Process of City Formation and Evolution in the Central Plateau of Iran, the Case of Sabzevar

The main cities of the central plateau of Iran are mostly located on the outer edge of the region. This distribution is determined by climatic impacts. Due to scarce precipitation and rapid evaporation of water for more than six months each year, the region lacks permanent rivers, and for that reason it was initially hard to establish permanent settlements. The population had to move between mountains and plains seasonally, until the invention of ‘qanats’ changed the way of life and settlement. By means of these underground aqueducts water was funnelled from mountainous areas and aquifers to lower lands. Alluvial fans could be opened up to settlement and an agrarian civilisation evolved. The qanat system is one of the important influences on the location and morphology of desert cities. By comparing old maps of the Sabzevar qanats and water routes with maps of historical streets and alleys in Sabzevar we found that the urban development pattern of Sabzevar is based on the transformation of farming lots to urban residential spaces. When in the course of urbanisation the fields were turned into houses with gardens, main streets were laid out along the course of main qanats and alleys along subsidiary channels. The resulting street pattern corresponds with the old irrigation network and, interestingly, the hierarchy of streets follows the hierarchy of the water distribution network.