ABSTRACT
Water is essential for life and an essential component of livelihood. These fundamental facts help explain why and where cities exist. Historically cities have been established near water sources that could support social and economic activities. Historically, city growth was controlled, among other factors, by the quantity and quality of nearby water. Aqueducts and sewers were built during the Roman Empire, as well as hydraulic infrastructure constructed by ancient civilizations in Asia, the Middle East and America. Yet, the basic need for a means to supply clean water to cities and remove dirty water from them has de facto changed little for millennia.
