The Hydrologic Evaluation of Landfill Performance (HELP) Model
for Simulating the Water Balance of Landfill Liner Systems

The HELP Model

The "Hydrologic Evaluation of Landfill Performance" (HELP) model was developed since 1982 by Dr. Paul Schroeder (U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi) and several coauthors for the U.S. Environmental Protection Agency (EPA). HELP version 1 was released in 1984, version 2 in 1988 and version 3 in 1994 (Schroeder et al. 1994a,b), current original version (September 2012) is HELP 3.07.

The HELP model is a "quasi-two-dimensional" layer model for estimating the water balance of open and closed landfills and especially of liner systems. Primary purpose is the comparison of design alternatives as judged by the water balance under the climate of the particular site. HELP models several hydrologic processes using a one-day time step. Vertical and lateral processes are combined, but a two-dimensional flow actually is not modeled (quasi-two-dimensional). Required input data are daily values of precipitation, air temperature and solar radiation of at least 1 and up to 100 complete calendar years, parameters to calculate evapotranspiration, data of soil and material properties, and data of the layer design and the site. The only vegetation considered are grasses, alternatively the soil may be bare. The layer profile must be constant during a simulation run. However, since HELP 3.80 D soil and material properties and the vegetation parameters can be changed in a simulation run, and since HELP 3.50 D the model estimates the evapotranspiration of shrubs and trees more realistically.

For ease of use HELP incorporates a data base with default soil data and the weather generator WGEN (Richardson & Wright 1984) together with a data base with parameters to calculate evapotranspiration and to generate daily weather data for locations in the USA and in Germany.

For HELP version 3 (Schroeder et al. 1994a,b) an extensive validation study under German climate was performed and the model was adapted for usage in Germany (Berger 1998). In the validation study limitations of HELP and errors were shown, conclusions for the user were drawn and approaches for an enhancement and further investigations needed were pointed out (see Berger 2000, 2002).

In a working group of the German Society for Geotechnics which accompanied the validation study the so called GDA-recommendation E 2-30 "Modeling the water balance of surface cover systems for landfills" (only in German) was developed that deals with recommendations for the usage of HELP in Germany. Furthermore, the working group developed the GDA-recommendations E 2-31 and E 2-32 dealing with the design of top soil layers and the vegetation.

Based on the results of the validation study and further investigations in the following years the enhanced HELP versions 3.50 D (2001), 3.55 D (2002), 3.80 D (2004) and HELP 3.90 D (2011) were developed. In these versions some bugs were fixed, the model was enhanced, the user interface was completely reprogrammed and the documentation was revised.

Enhanced Version HELP 3.90 D

With the current version HELP 3.90 D from October 2011 HELP-D was completely adapted to Windows. The following list summarizes the main modifications compared to the previous version HELP 3.80 D and some "highlights" of HELP 3.90 D:

• The DOS user interface was replaced by a Windows user interface which is also executable under 64-bit versions of Windows.
  The HELP model was adapted to Windows (especially path and file names may be longer than in DOS) and the weather generator was recompiled to be executable also under 64-bit Windows.
  HELP 3.9 D runs under Windows XP Prof. and Windows 7 (32-bit and 64-bit). Currently no experience concerning Windows Vista has been reported; however, I expect no problems running the model.
• User interface and model output are in English; the user's guide is available in English and in German language.
• Data input and model output may be in metric as well as in customary units as in HELP 3.07 (USA).
• HELP-D uses the same input file formats as HELP 3.07.
• The calculation of leap years was modified according to the Gregorian calendar.
• The import routines of HELP 3.0x (USA) for daily weather data of North American providers (NOAA Tape, Climatedata(TM) and Canadian Climatological Data) are no longer available in HELP 3.9 D because their programs cannot be executed under 64-bit Windows.
• The option Default Precipitation (5 years historic precipitation data) of HELP 3.0x (USA) is no longer available in HELP 3.9 D.
• In HELP 3.9 D the same data base and the same locations to synthetically generate daily weather data and to calculate evapotranspiration are available as in HELP 3.0x (USA).
• Due to a program modification the weather generator of HELP 3.9 D generates slightly different weather data beginning with the fifth year.
• An option to import data from Visual HELP files with evapotranspiration parameters and daily weather data was added, developed for files of Visual HELP version 2.2.
• The conversion factor for solar radiation from US-customary to metric units was specified more precisely. Therefore, usage of solar radiation data in metric units leads to slightly different simulation results with HELP 3.9 D.
• The soil data bases for US-American soil textures and other materials and for user defined and German soil textures were merged. The option of the user interface to store new user defined soil textures in the soil data base is no longer available. However, the data base file can be edited outside the HELP user interface with an editor.
• Since HELP 3.80 D the model outputs the daily, monthly and yearly simulation results as tables in separate output files for further processing in graphic or spreadsheet programs. The daily output is no longer written into the standard output file.
• If you are familiar with the original HELP 3.0x you should find HELP 3.90 D easy to use.

Enhancements of the HELP-D model:

Some of the sub-models were enhanced or replaced (actual evapotranspiration, vegetative growth and decay, frozen soil, unsaturated/saturated vertical flow in vertical percolation layers). Furthermore, since HELP 3.80 D HELP-D allows the user to change vegetation and soil properties in a simulation run to simulate the aging of a landfill profile for example the succession of the vegetation or the deterioration of lateral drainage layers due to clogging or of mineral liners due to desiccation and shrinkage. The following list summarizes the enhancements; detailed descriptions are given in Berger (2002) and in the supplement to the Engineering Documentation of HELP 3.90 D on the CD:

• Two implementation errors in the sub-model of unsaturated/saturated flow in vertical percolation layers were fixed.
• The lowest water content for unsaturated vertical flow in the evaporative zone was set to field capacity.
• A systematic error that occurs in some designs with drainage nets directly above the uppermost liner does no longer occur in HELP since 3.55 D due to the changing of the lowest water content for vertical flow. This error leads to a drastic underestimation of evapotranspiration.
• The frozen soil sub-model was pragmatically enhanced (shorter periods with frozen soil for Germany, freezing and thawing of the soil for just one segment per day), leading to a more realistic estimation of surface runoff and a better time distribution of lateral drainage in the drainage layer below the topsoil during and after thawing.
• The sub-models of evapotranspiration and vegetative growth and decay were enhanced:
  • The interception sub-model was replaced by an adapted empirical model of von Hoyningen-Huene. This model was developed for several crops, includes interception storage and allows calculating the interception of vegetation with larger values of the maximum leaf area index than for grasses.
  • Some errors in the soil evaporation sub-model were fixed leading to a more realistic relation between soil evaporation and transpiration and a more realistic influence of the vegetation on evapotranspiration.
  • The implementation of the vegetative growth and decay model was completed and the decrease of plant growth due to short air (aeration stress) was added from the model EPIC. In HELP 3.80 D the vegetative decay model was enhanced.
• Subsurface inflow into layers is no longer allowed in some cases that lead to invalid water balance results. Since HELP 3.80 D the summary output is correct also if monthly and yearly output were not selected.
• Since version 3.80 D HELP allows the user to change vegetation and soil properties in a simulation run to simulate the aging of a landfill profile. However, the layer (type) sequence must be constant. The user can input up to 10 sets of evapotranspiration and/or soil and design data for a simulation run.

Output comparisons of HELP 3.07 and HELP 3.90 D are available for the RCRA example of HELP 3.07 for Nashville (TN) and for Hamburg (Germany) .

Order of HELP-D

HELP 3.90 D can be ordered on account formless or on an order form by e-mail, fax or letter to Dr. Klaus Berger, Institute of Soil Science, University of Hamburg, Allende-Platz 2, 20146 Hamburg, Germany; Fax: +49 / 40 / 42838-2024:

Order procedure:

1. Optional: You ask me for a quote (prices for HELP 3.90 D see below).
2. You send me a purchase order (formless or on an order form) by e-mail, fax or letter with the delivery address for the CD and, if different, also the billing address where the invoice shall be sent.
3. a) I send the CD to the delivery address. Usually the CD will be delivered within 1 or 2 working days except for periods when I am absent. If you order by e-mail these periods will be stated by a corresponding automatic reply.
   b) The administration of the University of Hamburg sends the invoice to the billing address.
4. After receipt of the invoice you transfer the invoiced amount preferably by bank transfer else by cheque (no credit cards).

Prices:

The pricing is a bit complex due to the German/European value added tax (VAT) regulations:

¹ Delivery to the EU without value added tax requires that you state your value added tax identification number with your order.

Udate-orders are only available for registered HELP-D-users.

The prices include handling and shipping. There are no discounts.

Scope of delivery:

HELP 3.90 D is only available on CD and includes the program, a Getting Started instruction, and the following electronic documents in English as PDF:

• Berger, K. & P. Schroeder, 2012: The Hydrologic Evaluation of Landfill Performance (HELP) Model. User's Guide for HELP-D (Version 3.9 D). 5th, completely revised edition for HELP 3.9 D. Institute of Soil Science, University of Hamburg, Germany, 70 pp.
• Berger, K., 2011: The Hydrologic Evaluation of Landfill Performance (HELP) Model. Engineering Documentation for HELP 3.90 D - Enhancements Compared to HELP 3.07 -. Institute of Soil Science, University of Hamburg, Germany, 10 pp.

The CD also includes the previous versions HELP 3.80 D and HELP 3.07 (USA, the current original version including the User's Guide and Engineering Documentation as PDFs).

Note on the installation: The user interface of HELP 3.90 D uses the Microsoft .NET Framework 4 which is automatically installed with HELP if it is not on the computer. An internet connection is required for downloading the framework!

HELP-D Support

I am offering support for registered HELP-D users, preferably by e-mail. If you encounter problems, unexpected results or errors please have a detailed description with you.

References

• Berger, K., 1998: Validierung und Anpassung des Simulationsmodells HELP zur Berechnung des Wasserhaushalts von Deponien für deutsche Verhältnisse [Validation and Adaptation of the Simulation Model HELP for Calculating the Water Balance of Landfills for German Conditions]. Umweltbundesamt, Fachgebiet III 3.6 (PT AWAS des BMBF), Berlin, 569 pp. (in German, out of print)
• Berger, K., 2000: Validation of the Hydrologic Evaluation of Landfill Performance (HELP) Model for Simulating the Water Balance of Cover Systems. Environmental Geology 39 (11), pp. 1261-1274 (Article in pdf format online available at Springer-Verlag)
• Berger, K., 2002: Potential and Limitations of Applying HELP Model for Surface Covers. Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management, Vol. 6, No. 3, July 2002, pp. 192-203
• Berger, K. & P.R. Schroeder, 2011/2012: The Hydrologic Evaluation of Landfill Performance (HELP) Model. Version HELP 3.90 D. Institute of Soil Science, University of Hamburg, Germany
  CD, including the HELP program and electronic documents as PDF; manuals in English:
  
  • Berger, K. & P. Schroeder, 2012: The Hydrologic Evaluation of Landfill Performance (HELP) Model. User's Guide for HELP-D (Version 3.9 D). 5th, completely revised edition for HELP 3.9 D, 70 pp.
  • Berger, K., 2011: The Hydrologic Evaluation of Landfill Performance (HELP) Model. Engineering Documentation for HELP 3.90 D - Enhancements Compared to HELP 3.07 -. 10 pp.
• GDA-Empfehlung E 2-30, 2003: Modellierung des Wasserhaushalts der Oberflächenabdichtungssysteme von Deponien. Current version (in German)
• Melchior, S.; Sokollek, V.; Berger, K.; Vielhaber, B.; Steinert, B., 2010: Results from 18 Years of In Situ Performance Testing of Landfill Cover Systems in Germany. Journal of Environmental Engineering, 136 (8), ASCE, 518-523
• Richardson, C.W. & Wright, D.A., 1984: WGEN: A model for generating daily weather variables. ARS-8, USDA Agricultural Research Service, 83 pp.
• Schroeder, P.R. et al., 1994a,b: The Hydrologic Evaluation of Landfill Performance (HELP) Model. 2 Volumes: (a) User's Guide for Version 3; (b) Engineering Documentation for Version 3; EPA/600/R-94/168a,b; US Environmental Protection Agency, Cincinnati, Ohio (free download of model (DOS version) and documentation from the WES website)