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Model Report

WELLHEAD ANALYTIC ELEMENT MODEL FOR WINDOWS

Last Revision Date: 08/25/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

WHAEM2000
Model Extended Name:

WELLHEAD ANALYTIC ELEMENT MODEL FOR WINDOWS
Model Overview/Abstract:
WhAEM2000 (wellhead analytic element model for Win 98/00/NT/XP) is a public domain, ground-water flow model designed to facilitate capture zone delineation and protection area mapping in support of the State's and Tribe's Wellhead Protection Programs (WHPP) and Source Water Assessment Planning (SWAP) for public water supply wells in the United States. WhAEM2000 provides an interactive computer environment for design of protection areas based on radius methods, well in uniform flow solutions, and geohydrologic modeling. Protection areas are designed and overlaid upon US Geological Survey Digital Line Graph (DLG) or other electronic base maps. Base maps for a project can be selected from a graphical index map for the State. Geohydrologic modeling for steady pumping wells, including the influence of hydrological boundaries, such as rivers, recharge, no-flow boundaries, and inhomogeneity zones, is accomplished using the analytic element method. Reverse gradient tracelines emanating from the pumping center of known residence time are used to delineate the capture zones. WhAEM2000 has on-line help and tutorials.

Keywords: Capture zone delineation, source water/wellhead protection, analytic element method
Model Technical Contact Information:
Stephen R. Kraemer, Ph.D.
U.S. EPA Ecosystems Research Division
(706) 355-8340
kraemer.stephen@epa.gov
Model Homepage: http://www.epa.gov/athens/software/whaem/index.html
Substantive Changes from Prior Version: Version 3.2.1 released September 2007.

User Information Back to Top
Technical Requirements
Computer Hardware
80486 PC with 16 MB RAM and 25 MB ROM (minimum)
Compatible Operating Systems
Windows 98, NT, XP
Other Software Required to Run the Model
Visual Basic (GUI), Fortran (Solver)
Download Information
The model is publicly available from the U.S. EPA, Office of Research and Development (ORD), National Exposure Research Laboratory (NERL), Center for Exposure Assessment Modeling (CEAM).
Using the Model
Basic Model Inputs
Binary base maps or equivalent maps (shapefile, dxf) for representing hydrography, roads, hypsography.

Also aquifer geometry, hydraulic conductivity, porosity, recharge, well discharge.

Basic Model Outputs
Wellhead protection zones, tracelines, hydraulic head contours.
User Support
User's Guide Available?
The User's Guide, Working with WhAEM2000 (EPA/600/R-00/022) can be downloaded.
Availability of User Support
General support from the EPA Center for Exposure Assessment Modeling (CEAM) http://www.epa.gov/ceampubl/.

Training classes facilitated by the EPA Drinking Water Academy http://www.epa.gov/ogwdw/dwa/course-sourceprotect.html#delineation.

User Qualifications
The model supports beginning to intermediate users. A background in geology and ground water hydrology is useful.

Model Science Back to Top
Problem Identification
WhAEM2000 ground-water flow model designed to facilitate capture zone delineation and protection area mapping in support of the State's and Tribe's Wellhead Protection Programs (WHPP) and Source Water Assessment Planning (SWAP) for public water supply wells in the United States.

WhAEM2000 modeling system consists of a User interface written in Visual Basic 6, a mapping window provided by ESRI Map Object LT2, and the Fortran analytic element solver GFLOW1.exe written by Henk Haitjema.

Summary of Model Structure and Methods
The analytic element method was developed at the end of the seventies by Otto Strack at the University of Minnesota. There are two books about the analytic element method. "Groundwater Mechanics" by O. D. L. Strack, Prentice Hall , 1989, contains detailed mathematical descriptions of the analytic elements and their numerical implementation. "Analytic Element Modeling of Groundwater Flow" by H. M. Haitjema, Academic Press, 1995, provides the basic theoretical framework for the analytic element method and focuses on its use.

This new method avoids the discretization of a groundwater flow domain by grids or element networks. Instead, only the surface water features in the domain are discretized, broken up in sections, and entered into the model as input data. Each of these stream sections or lake sections are represented by closed form analytic solutions: the analytic elements. The comprehensive solution to a complex, regional groundwater flow problem is obtained by superposition of all, a few hundred, analytic elements in the model.

Traditionally, superposition of analytic functions was considered to be limited to homogeneous aquifers of constant transmissivity. However, by formulating the groundwater flow problem in terms of appropriately chosen discharge potentials, rather than piezometric heads, the analytic element method becomes applicable to both confined and unconfined flow conditions as well as to heterogeneous aquifers.

The analytic elements are chosen to best represent certain hydrologic features. Areal recharge is modeled by areal source distributions (areal sinks with a negative strength). Streams and lakes that are not fully connected to the aquifer are modeled by line sinks or area sinks with a bottom resistance. Discontinuities in aquifer thickness or hydraulic conductivity are modeled by use of line doublets.

Model Evaluation
The EPA Quality Assurance Project Plan: Tools and Techniques for Source Water Protection of Public Water Supply Wells, April 2003 documents the project testing procedures. The document GFLOW1 Verifications by Henk Haitjema (2003) describes the details of the solver verifications.

Heather A Raymond, Michael Bondoc, John McGinnis, Kathy Metropulos, Pat Heider, Allison Reed, Steve Saines (2006) Using Analytic Element Models to Delineate Drinking Water Source Protection Areas Ground Water 44 (1) , 16–23 doi:10.1111/j.1745-6584.2005.00122.x

Richard M. Yager, Christopher J. Neville (2002) GFLOW 2000: An Analytical Element Ground Water Flow Modeling System Ground Water 40 (6) , 574–576 doi:10.1111/j.1745-6584.2002.tb02543.x

WR Dripps, RJ Hunt, MP Anderson (2006) Estimating Recharge Rates with Analytic Element Models and Parameter Estimation Ground Water 44 (1) , 47–55 doi:10.1111/j.1745-6584.2005.00115.x

Key Limitations to Model Scope
WhAEM2000 is limited to representing average flow conditions in aquifers (steady state). The conceptual model is limited to single layer aquifers with horizontal base under either confined, unconfined flow, or mixed flow conditions. Solutions are for unbounded domains, although no-flow line elements may be superimposed. Resistance to vertical flow is neglected under Dupuit assumptions; however, three-dimensional streamlines can be approximated assuming continuity of flow. Aquifer inhomogeneities in hydraulic conductivity, porosity, base elevation, recharge rate, are represented with piece-wise homogeneous polygons. Contaminant transport is represented by advective pathline analysis of water parcels; residence times do not account for sorption, retardation, or decay . Dispersion is not represented.
Case Studies
The EPA Report “Working with WhAEM2000” includes a case study for a public water system in a glacial outwash valley. http://www.epa.gov/ceampubl/gwater/whaem/User_Manual.PDF


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