Page 59 - Hydrogeology Principles and Practice

HYDC02 12/5/05 5:38 PM Page 42

42 Chapter Two

BO X
Continued
2.5

exploitation, this groundwater eventually discharged into the throughout much of the London Basin. The potentiometric surface
Thames estuary in the Woolwich area via springs (Marsh & Davies of the Chalk aquifer was typically at shallow depth and in low-lying
1983). areas, such as the Hackney Marshes, water seeped upwards to the
The first deep boreholes were sunk in the middle of the eigh- surface. In Central London, the natural potentiometric surface was a
teenth century, and there was rapid development from about 1820. few metres above sea level (+7.5 m; Fig. 2a) creating artesian
At this time, as shown in Fig. 2a, an artesian situation existed groundwater conditions. At the start of the twentieth century, rest

Fig. 2 Maps of the Chalk potentiometric
surface in London showing groundwater
levels (a) before groundwater exploitation
commenced in the early 1800s and (b) in
1950. After Marsh and Davies (1983).