SIMULATION OF PESTICIDE CONCENTRATIONS IN GROUNDWATER USING AGRICULTURAL DRAINAGE AND PESTICIDE TRANSPORT (ADAPT) MODEL

A water quality model for subirrigation and subsurface drainage, ADAPT (Agricultural Drainage And Pesticide Transport), was tested with fiel d data collected under various water table management practices near A mes, IA. Atrazine and alachlor concentrations at various soil depths f or water table depths of 30, 60, and 90 cm were simulated using ADAPT model for corn growing seasons of 1989 through 1991. Daily pesticide c oncentrations in groundwater predicted by the model were compared with available observed data for the same site. Predicted values of atrazi ne and alachlor concentrations in groundwater decreased when shallow w ater table depths were maintained in the lysimeters. Similar trends we re noticed with the observed data. Reasonable agreement was obtained b etween the observed and predicted values of atrazine and alachlor for 1989 to 1991. However, in few cases, results showed a wide variation b etween observed and predicted values. Because no observed data was ava ilable for pesticide concentrations in the unsaturated zone, predicted results could not be compared. Based on our investigation, it appears that ADAPT may be used for predicting subsurface water quality under water table management practices, however, further validation is neces sary with more field observed data from similar studies before wider a pplication of this model is made. (C) 1998 Elsevier Science B.V.