The Hydrological Effects of Gravel Winning in an Area West of London, United Kingdom

The ground-water flow and ground-water quality of extensive gravel deposits in the Lower Colne Valley, near London, England are described. The great demand for aggregates in southeast England over the past 30 years has resulted in extensive exploitation of these gravels, the worked-out pits being either left water-filled for recreational purposes, or filled with a variety of waste materials. Both after-uses are shown to alter the ground-water situation either by locally lowering or raising ground-water levels, such effects having been described in both French and German literature, or by causing ground-water and surface-water pollution problems. If the scale of pit development or landfilling is large as in the Lower Colne Valley, then remedial measures have to be undertaken to minimize the pollution risk and to obviate problems caused by raised or lowered ground-water levels.