Annual report : April 1, 1995-March 31, 1996 : an intelligent integrated saltwater intrusion modelling system

The first investigates the problem of a sharp interface between salt and fresh waters in an aquifer of spatially variable permeability. Layered structure, with permeability a stationary random function of the vertical coordinate, of given mean and two point covariance, is considered. Exact analytical solution of two-dimensional steady flow of fresh water in a confined aquifer, with salt water in rest, is derived. Also, the uncertainty of the discharge of a coastal collector for a given depth of the upconed interface is examined. By using conditional probability, the impact of measurement of the interface depth in a given cross-section, on the reduction of the uncertainty of its position is determined. Also investigated is the generalization of Keulegan solution of unsteady flow that results from an abrupt removal of a thin vertical partition between salt and fresh water bodies. In the second report, the location of sharp interface between salt and freshwater in coastal aquifer is determined using optimization techniques. The algorithm is based on the combination of a nonlinear programming and an h-adaptive boundary element method. The objective is to create to an automated solution procedure. The effectiveness of the model is demonstrated using several examples in confined and unconfined aquifers. The unconfined aquifer cases require the simultaneous determination of an interface and a free surface. Includes references. (Author abstract)