The program 'WHPA' is a modular, semi-analytical ground-water flow model designed to assist State and local technical staff with Well-head Protection Area (WHPA) delineation. The model, developed for U.S. EPA, consists of 4 independent computational modules that may be used to delineate capture zones. All of the modules contain semi-analytical capture zone solutions; they are applicable to homogeneous aquifers that exhibit two-dimensional, steady-state ground-water flow in an areal plane with the option to compute hydraulic heads. Multiple pumping and injection wells may be present. Barrier or stream boundary conditions which exist over the entire aquifer depth may be simulated. One of the modules is based on the Monte Carlo approach to determine uncertainty in the computed results. One of the modules is a general particle-tracking routine that may be used as a post-processor for two-dimensional numerical ground-water flow models. Because this module may use the hydraulic heads output from a numerical model to delineate capture zones, the hydrogeological scenarios that may be investigated are only limited by the capabilities of the numerical model.

Data input, computational control, and on-screen preview of graphic output is facilitated by a user-friendly, menu-driven interface with help screens. WHPA produces tabular and graphical output which can be printed or saved in HPGL format or XYZ format for use in commercial contouring packages. WHPA is distributed on DOS formatted diskettes containing executable image, and example data sets. The user's manual includes installation instructions and program documentation.

SYSTEM REQUIREMENTS

• Intel 80i86 based computer
• 640 Kb RAM (about 590 Kb free memory)
• CGA, EGA, VGA graphics
• at least 500 Kb free disk space
• DOS 2.1 or higher
• math coprocessor optional
• HPGL plotter

Author: T. N. Blanford, P.S. Huyakorn, and Wu-Shu Wu (HydroGeologic Inc.)