GLEAMS WT HYDROLOGY SUBMODEL MODIFIED TO INCLUDE SUBSURFACE DRAINAGE/

The model GLEAMS-SWAT (GLEAMS with Subsurface drainage and WAter Table ) is a modified version of GLEAMS that accounts for shallow water tabl e fluctuations and subsurface drainage. The modification was accomplis hed by incorporating a subsurface drainage routine in GLEAMS-WT. Simul ation performances of GLEAMS and GLEAMS-SWAT were evaluated by compari ng their predictions with seven years (1981-1987) of measured data fro m a runoff-erosion-drainage experimental plot at Baton Rouge, Louisian a. Validations to test the accuracy of GLEAMS-SWAT predictions of surf ace runoff volume, subsurface drainage volume, total volume (surface r unoff + subsurface drainage), and water table depth were satisfactory. Total predicted surface runoff volume for the seven-year period was 9 4% of the observed runoff volume, an improvement from GLEAMS underpred iction of surface runoff volume which was 71% of the observed runoff. Subsurface drainage volume and total drainage (runoff + subsurface dra inage) volume predictions were, respectively, 99% and 96% of the obser ved volumes. Water table depth prediction was deeper than the observed depth, especially during the pregrowing and growing seasons.