Version 3.04 (April 1995)
Order No: FOS 32
The Hydrologic Evaluation of Landfill Performance (HELP) model was developed to help hazardous waste landfill designers and regulators evaluate the hydrologic performance of proposed landfill designs. The model accepts weather, soil and design data and uses solution techniques that account for the effects of surface storage, snowmelt, runoff, infiltration, evapotranspiration, vegetative growth, soil moisture storage, lateral subsurface drainage, leachate recirculation, unsaturated vertical drainage, and leakage through soil, geomembrane or composite liners. Landfill systems including various combinations of vegetation, cover soils, waste cells, lateral drain layers, low permeability barrier soils, and synthetic geomembrane liners may be modeled. Results are expressed as daily, monthly, annual and long-term average water budgets.
The HELP model is a quasi-two-dimensional, deterministic, water-routing model for determining water balances. The model was adapted from the EPA HSSWDS model and various models of the U.S. Agricultural Research Service (ARS), including the CREAMS and SWRRB models, and the SNOW-17 routine of the National Weather Service River Forecast System (NWSRFS) and the WGEN synthetic weather generator.
Version 3 of the HELP model has been greatly enhanced beyond versions 1 and 2. The number of layers that can be modeled has been increased. The default soil/material texture list has been expanded to contain additional waste material, geomembranes, geosynthetic drainage nets and compacted soils. The model also permits the use of a user-built library of soil textures. Computations of leachate recirculation and groundwater drainage into the landfill have been added. HELP Version 3 also accounts for leakage through geomembranes due to manufacturing defects (pinholes) and installation defects (punctures, tears and seaming flaws) and by vapor diffusion through the liner. The estimation of runoff from the surface of the landfill has been improved to account for large landfill surface slopes and slope lengths. The snowmelt model has been replaced with an energy-based model; the Priestly-Taylor potential evapotranspiration model has been replaced with a Penman method, incorporating wind and humidity effects as well as long wave radiation losses (heat loss at night). A frozen soil model has been added to improve infiltration and runoff predictions in cold regions. The unsaturated vertical drainage model has also been improved to aid in storage computations. Input and editing have been further simplified with interactive, full-screen, menu-driven input techniques.
Version 3 of HELP comes with a new set of manuals. HELP is a public domain program which runs under MS-DOS. The user's manual includes installation instructions, theory, user's instructions, example problems, and data tables.
Intel 80i86 with math coprocessor, 640 Kb (conventional) RAM, DOS 3.1 or higher, 3 Mb free disk space for program and example files.
Authors: R. Lee Payton (Univ. Of Missouri-Columbia) and Paul Schroeder (U.S. Army Corps of Engineers)