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FEMWATER/LEWASTE: Numerical Codes for Delineating Wellhead Protection Areas in Agricultural Regions Based on the Assimilative Capacity Criterion

The Three-Dimensional Finite Element Model of Water Flow Through Saturated-Unsaturated Media (3DFEMWATER or FEMWATER) model is designed to provide a numerical procedure for establishing wellhead protection zones (in agricultural areas) using the assimilative capacity criterion. FEMWATER is a three-dimensional variably saturated zone model that models contaminant movement in heterogeneous and anisotropic media consisting of many geologic formations as desired, considers both distributed and point sources/sinks that are spatially and temporally dependent, and accept four types of boundary conditions.
Input and output are through files.

FEMWATER and LEWASTE (Three-Dimensional Lagrangian-Eulerian Finite Element Model of Waste Transport Through Saturated-Unsaturated Media) are related and can be used together to model flow and transport in three dimensional, variably-saturated porous media under transient conditions with multiple distributed and point sources/sinks. These models can be used to apply the assimilative capacity criterion to development of wellhead protection areas, as each U.S. state is required to do under the 1986 Amendments to the Safe Drinking Water Act. The complexity of 3DFEMWATER/3DLEWASTE numerical models requires that they be used by experienced numerical modelers with strong background in hydrogeology.

Both codes

  1. treat heterogeneous and anisotropic media consisting of as many geologic formations as desired,
  2. consider both distributed and point sources/sinks that are spatially and temporally dependent, and
  3. accept four 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 on 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, Freundlich, or Langmuir isotherm, dispersion, and first-order decay.

The complexity of 3DFEMWATER/3DLEWASTE numerical models requires that they be used by experienced numerical modelers with strong background in hydrogeology.
Femwater can be driven by the sophisticated (but rather expensive) graphic pre- and postprocessing enviroment GMS.

KEYWORDS

area: ground water
objectives: simulation
description: water flow, water quality, finite element method, first-order pollutant decay, transient conditions, stationary conditions

SOFTWARE AVAILABILITY

Center for Exposure Assessment Modeling (CEAM)
U.S. Environmental Protection Agency
Office of Research and Development
Environmental Research Laboratory
960 College Station Road
Athens, Georgia 30605-2720
Tel. 706/546-3549
The GMS-version of FEMWATER can be obtained from GMS Home Page.

The code can be downloaded at EPA CEAM Femwater site

AUTHORS

  • original code:
    G.T. (George) Yeh
    The Pennsylvania State University
    University Park, PA 16802

  • upgraded the code to EPA coding conventions:
    Robert Strobl
    The Pennsylvania State University
    University Park, PA 16802

  • reviewed the code and suggested modifications:
    John Kittle
    AQUA TERRA Consultants
    Mountain View, CA 94043

REFERENCES

  • Yeh G.T., S. Sharp-Hansen, B. Lester, R. Strobl and J. Scarbrough 1992: 3DFEMWATER/3DLEWASTE: NUMERICAL CODES FOR DELINEATING WELLHEAD PROTECTION AREAS IN AGRICULTURAL REGIONS BASED ON THE ASSIMILATIVE CAPACITY CRITERION Office of Research and Development, Environmental Protection Agency, Athens, GA. EPA/600/R-92/223 278 pp.
  • U.S. Environmental Protection Agency. 1987. Guidelines for Delineating Wellhead Protection Areas. EPA No. 440/6-87-010. Office of Groundwater Protection, U.S. Environmental Protection Agency, Washington, DC. NTIS No. PB88-111430-AS.
  • U.S. Environmental Protection Agency. 1989. Transport and Fate of Contaminants in the Subsurface: Seminar Publication. EPA/625/4-89/019. Center for Environmental Research Education, U.S. Environmental Protection Agency, Cincinnati, OH.

 

 

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