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About The HELP Model
The HELP model is a quasi-two-dimensional, deterministic, water-routing model for determining water balances. The following is a description of the
HELP model as derived from the HELP program reference manual:
The HELP program was developed by the U.S. Army Engineer Waterways Experiment Station (WES), Vicksburg, MS, for the U.S. Environmental Protection
Agency (EPA), Risk Reduction Engineering Laboratory, Cincinnati, OH, in response to needs in the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation and Liability
Act (CERCLA, better known as Superfund) as identified by the EPA Office of Solid Waste, Washington, D.C. The primary purpose of the model is to assist in the comparison of landfill design alternatives as judged by
their water balances.
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 original version of the HELP model was first developed at WES in 1984 (Schroeder et al., 1984a and 1984b). Since then there have been many
advances in the technology and scope of the model and many of the defects in the code have been corrected. The latest version of the HELP model is version 3.07 which contains many significant improvements and
enhancements over the previous versions. The following is a brief outline of the enhancements that have been made since Version 2 of the HELP model (Schroeder et al., 1988a and 1988b).
- The number of layers that can be modeled has been increased
- The default soil material texture list has been expanded to contain additional waste materials, geomembranes, geosynthetic drainage nets and
compacted soils
- The model now permits the use of customized soil textures
- Computations of leachate recirculation and groundwater drainage into the landfill have been added
- Leakage through the geomembranes due to manufacturing defects (pinholes) and installation mishaps (tears and punctures) is accounted for
- Estimation of surface runoff has been improved to account for large landfill surface slopes and slope lengths
- The snow-melt model has been replaced with an energy-based model
- The Priestly-Taylor potential evapotranspiration model has been replaced with a Penman method that incorporates wind and humidity effects as
well as long-wave radiation heat losses
- A frozen soil model has been added to improve infiltration and evapotranspiration predictions in cold regions
- The unsaturated vertical drainage model has also been improved to aid in storage computations
Visual HELP includes the latest version of the HELP model. Continued work with the original developer of the HELP model (Dr. Paul Schroeder) is
being done to improve it to suit the advancing technology requirements of landfill engineers.
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