EVALUATION OF THE HYDROLOGIC COMPONENT OF THE ADAPT WATER-TABLE MANAGEMENT MODEL

A subsurface, water table management model ADAPT (Agricultural Drainage and Pesticide Transport) has been developed by combining drainage and subirrigation algorithms from DRAINMOD with the GLEAMS model. In addition, the model incorporates improved snow melt and runoff algorithms, macropore flow due to cracking, and deep seepage. Theory for the hydrologic components of the model is presented together with an evaluation of the model using data from a long-term field experiment at Castalia in North Central Ohio. Predicted surface runoff, subsurface drainage, and combined surface and subsurface drainage are compared with the field observations. In general, the model predictions are within the range of the variations of the observed replications. Sensitivity analysis shows that surface runoff estimates are sensitive to changes in curve number, while subsurface drainage flows are sensitive to deep seepage estimates. Model input requirements are not excessive and the model gives reasonable estimates of the hydrologic component of water table management systems. ADAPT can be used in designing water table management systems and does not require extensive calibration. The pesticide component of ADAPT is currently being evaluated and development of a nutrient component has been initiated.