Grantee Research Project Results
2004 Progress Report: Evaluation of Hydrologic Models for Alternative Covers at Mine Waste Sites
EPA Grant Number: R829515C007Subproject: this is subproject number 007 , established and managed by the Center Director under grant R829515
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Human Models for Analysis of Pathways (H MAPs) Center
Center Director: Murphy, William L
Title: Evaluation of Hydrologic Models for Alternative Covers at Mine Waste Sites
Investigators: Shackelford, Charles D. , Benson, Craig H.
Institution: Colorado State University , University of Wisconsin - Madison
EPA Project Officer: Aja, Hayley
Project Period: October 1, 2002 through September 30, 2005
Project Period Covered by this Report: October 1, 2003 through September 30, 2004
Project Amount: Refer to main center abstract for funding details.
RFA: Hazardous Substance Research Centers - HSRC (2001) Recipients Lists
Research Category: Hazardous Waste/Remediation , Land and Waste Management
Objective:
The overall objective of this research project is to evaluate the accuracy of five different hydrologic models (HELP, UNSAT-H, VADOSE/W, H ydrus-2D, and LEACHM) commonly used for the design of cover systems using high-quality field data from large-scale test facilities of alternative covers, with the ultimate aim of developing an improved, easy-to-use, and field-verified model for long-term assessment of alternative covers at a variety of sites and climatic conditions. The research project has four specific objectives:
- a baseline assessment and comparison of the algorithms in existing hydrologic models when applied to a variety of meteorological conditions;
- an unbiased critical assessment of the predictive capabilities of existing hydrologic models for covers using field data from the Alternative Landfill Cover Demonstration, Alternative Cover Assessment Program, and Rocky Mountain Arsenal;
- improvement of the hydrologic model (or models) that have the most promise so that predictions made with the model are accurate;
- and incorporation of additional algorithms in the model that can be used to assess the impact of long-term processes such as plant secession, pedogenesis, and climatic change.
Progress Summary:
Simulations using the VADOSE/W model with the same input data have been performed at both the University of Wisconsin and Colorado State University to assess the consistency in the results. The comparison of output results includes volumetric water content as well as water balance mechanisms such as cumulative runoff, cumulative precipitation, cumulative surface evaporation, cumulative storage, and cumulative water balance. Comparison of simulation results with field data also have been made among predictions from HYDRUS-2D, UNSAT-H, VADOSE/W, and LEACHM with field data from field sites. Finally, systematic evaluations of input parameters using each of the models to assess the relative impact (i.e., high, modest, low) on the water balance predictions also have been performed. Similar sensitivity analyses have been performed to date primarily with the UNSAT-H and HYDRUS-2D models on all components of the water balance (soil water storage, surface runoff, evapotranspiration, and percolation) for a limited number of sites. Additional simulations have been performed to evaluate the lower (outflow) boundary condition (LBC) used in the simulations. For example, a seepage face LBC has been recommended in the literature and typically used in practice, but the results of our simulations to date suggest that a unit gradient LBC may provide better correlations with field data and more conservative predictions. These results will be updated and possibly expanded as additional models and sites are evaluated and compared.
Future Activities:
We will finalize the third and fourth objectives in Year 3 of the project. The activities will include continued assembly of input files and conducting further comparative simulations.
Publications/Presentations: See the list of publications/presentations included in the 2004 Annual Report Summary for R829515, which is the overall report for the Rocky Mountain Regional Hazardous Substance Research Center.