A hypothesis concerning the dynamic balance of fresh water and salt water in a coastal aquifer

The dispersion of salts produced by reciprocative motion of the salt-water front in a coastal aquifer induces a flow of salt water from the floor of the sea into the zone of diffu- sion and back to the sea. The head losses that accompany the landward flow tend to lesson the extent to which the salt water occupies the aquifer. Introduction--Published explanations of the steady-state balance between salt water and fresh water in a coastal aquifer, beginning with Badon Ghyben (1889) and Herzberg (1901), commonly assume that the salt water is static. Under this assumption the balance would be as shown in Figure 1. The depth below sea level to a point on the interface would be (Hubbert, 1940, p. 872)