SIMULATION OF SALTWATER INTRUSION IN THE NORTHERN GUAM LENS USING A MICROCOMPUTER

A two-dimensional (areal) finite element model of saltwater intrusion was modified so that it can run on a microcomputer. The model assumes a sharp interface between fresh water and salt water and simulates the movement of both fresh water and salt water. Linear triangular elements are used to discretize the domain. A preprocessor is used to renumber the nodes of a given network to reduce the bandwidth of the matrix. The model was applied to the Northern Guam aquifer. The hydraulic conductivity in three regions of the aquifer was calibrated using the water-level history for a few observation wells. Field measurements of the depth of the interface indicate that the sharp interface assumption is valid for most of the aquifer. Comparison of the depth of the measured 50% isochlor with the computed depth of the interface shows that the two are equal at most locations. In some cases, the computed depth is less than the measured depth which results in a conservative estimate of the interface depth. © 1990.