GLEAMS-WT Hydrology Submodel Modified to Include Subsurface Drainage

Abstract

The model GLEAMS-SWAT (GLEAMS with Subsurface drainage and WAter Table) is a modified version of GLEAMS that accounts for shallow water table fluctuations and subsurface drainage. The modification was accomplished by incorporating a subsurface drainage routine in GLEAMS-WT. Simulation performances of GLEAMS and GLEAMS-SWAT were evaluated by comparing their predictions with seven years (1981-1987) of measured data from a runoff-erosion-drainage experimental plot at Baton Rouge, Louisiana. Validations to test the accuracy of GLEAMS-SWAT predictions of surface runoff volume, subsurface drainage volume, total volume (surface runoff + subsurface drainage), and water table depth were satisfactory. Total predicted surface runoff volume for the seven-year period was 94% of the observed runoff volume, an improvement from GLEAMS underprediction of surface runoff volume which was 71% of the observed runoff. Subsurface drainage volume and total drainage (runoff + subsurface drainage) volume predictions were, respectively, 99% and 96% of the observed volumes. Water table depth prediction was deeper than the observed depth, especially during the pregrowing and growing seasons.