How did water supplies limit the size and location of early cities?

Water supplies were a fundamental factor in the location and growth of early cities, as access to fresh water was essential for survival, sanitation, and agriculture.12

Location and Early Settlement

The earliest permanent settlements were typically established near natural water sources such as rivers, lakes, and springs. These riparian sites provided immediate access to water for drinking and irrigation, which allowed for the development of sedentary communities and the agricultural surpluses necessary to support growing populations. In arid environments, this dependence on rivers was often a matter of necessity, leading to the rise of "hydraulic civilizations" that required sophisticated engineering to manage floodplains and irrigation.12

Limitations on City Size

As urban populations grew, the limitations of local water sources became a significant constraint. Early cities were restricted by the volume of water available from nearby wells or rivers. To overcome these limits, civilizations developed advanced conveyance systems:2
* Qanats: Ancient systems in Persia and the Middle East used tunnels to tap into groundwater and transport it via gravity to cities.32
* Aqueducts: The Romans built extensive networks of aqueducts to bring water from distant springs and rivers, allowing cities to grow far beyond the capacity of their immediate surroundings.32

Without such infrastructure, a city’s size was effectively capped by the reach of its local water supply.2