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AN EVALUATION AND ANALYSIS OF THREE DYNAMIC WATERSHED ACIDIFICATION CODES (MAGIC, ETD, AND ILWAS)
Citation:
Jenne, E., L. Eary, L. Vail, D. Girvin, A. Liebetrau, L. Hibler, T. Miley, AND M. Monsour. AN EVALUATION AND ANALYSIS OF THREE DYNAMIC WATERSHED ACIDIFICATION CODES (MAGIC, ETD, AND ILWAS). U.S. Environmental Protection Agency, Washington, D.C., EPA/600/3-89/045 (NTIS PB89006388), 1989.
Description:
The U.S. Environmental Protection Agency is currently using the dynamic watershed acidification codes MAGIC, ILWAS, and ETD to assess the potential future impact of acidic deposition on surface water quality by simulating watershed acid neutralization processes. The reliability of forecasts made with these codes is of considerable concern. The present study evaluates the process formulations (i.e., conceptual and numerical representation of atmospheric, hydrologic, geochemical and biogeochemical processes), compares their approaches to calculating acid neutralizing capacity (ANC), and estimates the relative effects (sensitivity) of perturbations in the input data on selected output variables for each code. Input data were drawn from three Adirondack (upstate New York) watersheds: Panther Lake, Clear Pond, and Woods Lake. Code calibration was performed by the developers of the codes. Conclusions focus on summarizing the adequacy of process formulations, differences in ANC simulation among codes and recommendations for further research to increase forecast reliability.