You have entered the website of the Water and Environmental Research Institute of the Western Pacific (WERI) at the University of Guam. We are currently six faculty and five staff and our mission is to seek solutions through research, teaching and outreach programs, to issues and problems associated with the location, production, distribution and management of freshwater resources in Guam, the CNMI and the FSM.
A two-dimensional, finite element model has been developed to simulate saltwater intrusion into coastal and insular groundwater aquifers. The depth-averaged equations of continuity for freshwater and saltwater are solved simultaneously with the assumption of a sharp interface separating the two liquids. The aquifer is discretized into linear, triangular elements. The Galerkin weighted residual method was used to develop element equations. Boundary conditions of the Dirichlet and Neumann type can be applied. A third type (Cauchy) boundary condition is used where freshwater exits along the coastline.
A computer program has been written in FORTRAN to solve for the freshwater and saltwater heads at each node of the finite element grid. The program can simulate steady or unsteady conditions in phreatic or confined aquifers. Wells can be specified at any node. The pump rate, aquifer recharge rate and boundary conditions can be specified as functions of time. The program can track the location of the saltwater toe (where the phreatic surface touches the impervious basement). The program can provide the magnitude and direction of the fresh and salt water in each element of the grid. The program can also be used to simulate aquifers that have only fresh water by specifying the saltwater head at all nodes to be much lower than the expected fresh water head.
The solution has been checked for accuracy against the following analytic solutions:
The model has also been applied to natural aquifers for management and future planning purposes.
