Report Number: 11
Year: 1980

A Review of Techniques for Studying Freshwater/Seawater Relationships in Coastal and Island Groundwater Flow Systems

This report reviews and summarizes the analytic and numeric methods available for the study of saltwater intrusion into freshwater aquifers in coastal and island situations. The methods are divided into three categories. The first deals with closed-form analytic solutions of steady interface problems using the hodograph method. In these problems, the saltwater and freshwater are separated by an abrupt interface, and the location of this interface is determined for simple aquifer geometries and boundary conditions. These solutions can also be used to test the accuracy of numerical techniques. The second category of methods deals with solutions utilizing the Dupuit and Ghyben-Herzberg approximations. The unsteady equations on one- and two-dimensions that need to be solved are presented. Numerical approximations of these differential equations are suggested and results reported in the literature. The last category of methods deals with numerical solutions of the convection-dispersion equation. A finite element solution of the equations applied to a vertical, two-dimensional plane is presented. This method results in the concentration of salt as a function of space and time. The advantages and limitations of all the methods are discussed.

Dinshaw N. Contractor