Cities and their water resources
Visiting Cambridge, I had the opportunity to revisit Nine Wells, to the south of Cambridge which was the main new source of water for the city, developed between 1610 and 1614, about the same time as the New River was being built to serve London as it happens.
The nine wells are in fact chalk springs draining into a long pond, such sparking clear water you can hardly see it in the photo. This pond forms the starter point for Hobson's Conduit, an open channel taking the spring water 4.5km into Cambridge. Wikipedia telling us that 'it became the principal water supply for Cambridge for over 250 years. Water continues to flow into the city and waters the lake in the Botanic Gardens.'
What intrigues me was to see the extent of the city's extension towards this (now unused) water resource. Looking at an online map of the city from about 1600 it appears that the conduit ran through open countryside for 4km before reaching the edge of the town.
Now, with the expansion of Addenbrookes Hospital and the 'Biomedical Campus' this water resource is just 200 metres beyond the Campus boundary.
Nine Wells is hidden within the stretch of trees highlighted. And, thanks to Google Earth, it is possible to see the extent of urban expansion since 1945:
All this by way of illustrating the challenges all urban areas face, particularly those in some parts of the world projected to reach more than 50 million inhabitants by the end of the century, and that water planners, engineers and hydro-geologists always have to end up going further and further out of the city in order to find good water.
The only, small, comfort is that economies of scale kick in as the next distant, but large water resource is developed.