A quasi-two-dimensional modeling program that simulates water movement into and out of landfills based on a waste management system=s particular design. The user can conduct water-balance analyses of solid waste disposal and containment facilities. The program allows comparison of proposed landfill designs by estimating runoff, evapotranspiration, drainage, leachate collection, and liner leakage. Modeling incorporates information on, for example, cover soils, waste cells, lateral drain layers, low permeability barrier soils, synthetic geomembrane liners, and weather. Results are expressed as daily, monthly, annual, and long-term water budgets. Although applicable to most landfills, HELP was developed specifically for modeling hazardous and municipal solid waste landfills as required by RCRA.