On the new Hydrologic Evaluation of Landfill Performance (HELP) model version 4 for the water balance simulation of landfill liner systems

Abstract

23 years after the last original US HELP version 3.07, in 2020 the US Environmental Protection Agency released a new version, called HELP 4. With this Excel-based version, the original HELP model has arrived in the modern Windows world. However, the model itself remains HELP 3.07. The papers deals with experiences of the author using HELP 4 and compares simulation results of four HELP versions (HELP 4.0.1, DOS HELP 3.07, and HELP 3.07 and HELP 3.95 D included in HELP 3.95 D) for two applications. First, the RCRA example of the original HELP version 3 in (US) customary units for 30 years of synthetically generated weather data for Nashville, TN. Second, the water balance test field F1 on the landfill Georgswerder in Hamburg, Germany, for 1988 to 1995 in metric units. The user interface is easy to use; however, it is more restrictive than necessary and not usable outside the USA without having weather data files of HELP 3.07 for import. The average annual totals of all tested HELP 3.07 model versions are close together. Differences occur probably due to computer numeric and because HELP 4.0.1 neglects the last day of leap years. The computing times of HELP 4.0.1 are for a factor of about 50 larger than for HELP 3.07 included in HELP 3.95 D. Despite reasonable criticism that may be made, the HELP model is a valuable tool for those who are aware of its limitations and merits enhancements to match the current state of the art.