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Watershed Assessment Model (WAM): Model Use, Calibration, and Validation

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 55(4): 1367-1383. (doi: 10.13031/2013.42248) @2012
Authors:   A. B. Bottcher, B. J. Whiteley, A. I. James, J. G. Hiscock
Keywords:   GIS, Grid based, Hydrology, Land use, Nitrogen, Nutrient assimilation, Nutrient sources and cycling, Phosphorus, Water quality, Watershed modeling

The Watershed Assessment Model (WAM) is a GIS-based model that simulates the complex hydrology and water quality responses within a watershed based on detailed characterization data. The watershed is represented by a spatially scalable grid, for which one of three field-scale models determines the constituent (water, total suspended solids, biological oxygen demand, nitrogen, and phosphorus) balances of each cell on a daily basis. The constituents leaving each cell are subsequently transported via surface and subsurface flow to stream reaches using a topographic routing algorithm, accounting for the assimilative processes along the paths. The constituents reaching a stream are then routed through the reach network to the basin outfall. This algorithm handles dynamic water control structures, point sources, and complex branching and convergence. The outputs are reported at the source cell, as delivery to reaches, and as output from reaches. The application and calibration of the model for the C-139 basin in south Florida resulted in good matches between simulated and observed flows and total phosphorus (TP) concentrations and loads at multiple outlet points around the basin, including multiple control structure operations and temporal TP concentration dynamics.

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