3DFEMWATER/3DLEWASTE: Numerical Codes for Delineating Wellhead Protection Areasin Agricultural Regions Based on the Assimilative Capacity Criterion

摘要

Two related numerical codes, 3DFEMWATER and 3DLEWASTE, are presented that can beused to delineate wellhead protection areas in agricultural regions using the assimilative capacity criterion. 3DFEMWATER (Three-dimensional Finite Element Model of Water Flow Through Saturated-Unsaturated Media) simulates subsurface flows, whereas 3DLEWASTE (Hybrid Three-dimensional Lagrangian-Eulerian Finite Element Model of Waste Transport Through Saturated-Unsatured Media) models contaminant transport. Both codes treat heterogeneous and anisotropic media consisting of as many geologic formations as desired, consider both distributed and point sources/sinks that are spatially and temporally dependent, and accept for types of boundary conditions--i.e., Dirichlet (fixed-head or concentration), specified-flux, Neumann (specified-pressure-head gradient or specified-dispersive flux), and variable. The variable boundary condition in 3DFEMWATER simulates evaporation/infiltration/seepage at the soil-air interface and, in 3DLEWASTE, simulates mass infiltration into or advection out of the system. 3DLEWASTE contains options to model adsorption using a linear, Fruendlich, or Langmuir isothern, plus dispersion, and first-order decay.