Cities used to be centres of plague and illness. During the past 150 years urban sanitary engineering and medical epidemiology have promoted rapid improvements to human health in the cities of the industrial world. A celebrated example was the pioneering work of Dr. John Snow who, in the mid-19th century, traced the source of a London cholera epidemic to a public water pump on Broad Street. Most cities evolved from small settlements and the availability of a suitable water supply was often the primary factor in their location. Often, though, these original water sources quickly became inadequate in quality or quantity, and sometimes are now completely forgotten. New sources and larger quantities of water were required. Groundwater may have been drawn from deep aquifers, even from beyond city boundaries. Today, groundwater plays a critical but complex (and pften largely unrecognized) role in the urban environment.
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