Mr R. A. Fox writes: Mr Oteri's paper presents a limited review of the aquifer at Dungeness. However, the problem of saline intrustion is a complicated one and we would like to comment on several aspects where the content of the paper may be misleading.
On page 48, the author notes that the lowest resistivity layer was interpreted as representing a saline water-saturated fine sand interface, which was accepted as the fresh water-saline water interface. He then goes on to note on page 49 that ’the depth of the fresh water-saline water interface beneath sea level in Dungeness is considerably smaller than that expected from the Ghyben-Herzberg principle‘. This states that, due to water density differences, the interface is about forty times deeper below mean sea level than the fresh water height is above sea level. A diagram to illustrate this point and the variations in interface level which apparently occur would be an interesting addition to the paper.
The conclusion on page 50 infers that gravel-winning from the aquifer, already thinner than expected, raises the level of the saline water and encourages the intrusion of the saline wedge in the coastal fringe. However, comparing Figs 1 and 7 it is evident that the areas of thinner fresh water lens are more directly associated with supply well locations than gravel-winning areas. This tends to be confirmed whenFig. 7 contours are superimposed on Fig. 2.
Ready Mixed Concrete (UK) Limited is one of the companies referred to in the introduction of