UPF: two-dimensional finite-element groundwater flow model for saturated-unsaturated soils

A finite-element program for modeling water flow in saturated-unsaturated s oils is presented. The program can handle non-uniform flow regions having i rregular boundaries and local anisotropy. The flow domain can be either in a vertical or in a horizontal plane, or in a three dimensional system with radial symmetry. The flow equation is solved by using either a Galerkin fin ite-element (GFE), or a control-volume finite-element (CVFE) method. The di scretization of the flow domain is obtained by using triangular finite elem ents and linear shape functions; the integration in time is performed by a finite-difference (FD) Picard scheme. Different schemes of the 'upstream' a nd 'lumping' procedures in computing, respectively, the conductivity and ca pacity matrices are compared. taking as evaluation parameters the global ma ss balance errors and the stability of the solutions. The listing of the FO RTRAN 77 source code, along with the user manual, the description of the su broutines used in the code, and four input files for four test cases are av ailable by anonymous FTP from ftp.iamg.org site or may be downloaded by Int ernet from http://www.iamg.org/CGEditor/index.htm. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.