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Title: MODELS FOR HYDROLOGIC DESIGN OF EVAPOTRANSPIRATION LANDFILL COVERS

Author
item HAUSER, V - MITRETEK SYSTEMS
item GIMON, D - MITRETEK SYSTEMS
item Bonta, James - Jim
item Howell, Terry
item Malone, Robert - Rob
item WILLIAMS, J - TEXAS AGRI EXP STATION

Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2005
Publication Date: 8/5/2005
Citation: Hauser, V.L., Gimon, D.M., Bonta, J.V., Howell, T.A., Malone, R.W., Williams, J.R. 2005. Models for hydrologic design of evapotranspiration landfill covers. Journal of Environmental Science and Technology. 39(18):7226-7233.

Interpretive Summary: Landfill covers are often used to minimize the movement of percolating rain water through soil so water that will not contact hazardous wastes that have been buried. This minimizes the opportunity for water to transport the wastes to ground water or a downstream point. Landfill covers typically use an artificial, impervious barrier to prevent water from coming in contact with the buried wastes. However, the technology used in landfill covers is changing, and an alternative cover called the evapotranspiration (ET) landfill cover is coming into use. This type of cover is specially designed to maximize evapotranspiration from the soil overlying the buried waste, precluding the need for an impervious barrier. The design of the cover accounts for the complex interaction of plants, soils, and climate. Important design requirements are prescribed by federal rules and regulations for conventional landfill covers but not for ET landfill covers. Also, there is no accepted hydrologic model for ET landfill cover design. This paper describes ET cover requirements, design issues, and assesses the accuracy of the EPIC and HELP hydrologic models when used for hydrologic design of ET covers. We tested the models against high quality field measurements available from lysimeters maintained by the Agricultural Research Service of the U.S. Department of Agriculture at Coshocton, Ohio and Bushland, Texas. The HELP model produced substantial errors in estimates of hydrologic variables. The EPIC model estimated ET and deep percolation with errors less than 7 percent and 5 percent, respectively, and accurately matched extreme events with an error of less than two percent of precipitation. The EPIC model is better suited for use in hydrologic design of ET landfill covers than the HELP model. The research will be useful to consulting engineers and regulators for designing and regulating ET landfill covers, with the potential to save millions of dollars compared with typical barrier type covers.

Technical Abstract: The technology used in landfill covers is changing, and an alternative cover called the evapotranspiration (ET) landfill cover is coming into use. Important design requirements are prescribed by federal rules and regulations for conventional landfill covers but not for ET landfill covers. There is no accepted hydrologic model for ET landfill cover design. This paper describes ET cover requirements, design issues, and assesses the accuracy of the EPIC and HELP hydrologic models when used for hydrologic design of ET covers. We tested the models against high quality field measurements available from lysimeters maintained by the Agricultural Research Service of the U.S. Department of Agriculture at Coshocton, Ohio and Bushland, Texas. The HELP model produced substantial errors in estimates of hydrologic variables. The EPIC model estimated ET and deep percolation with errors less than 7 percent and 5 percent, respectively, and accurately matched extreme events with an error of less than two percent of precipitation. The EPIC model is suitable for use in hydrologic design of ET landfill covers.