Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

Using a model as a management tool requires testing of the model against field measured data prior to its application for solving natural resource problems. This study was designed to calibrate and evaluate the subsurface drainage component of the Soil Water Assessment Tool (SWAT) model for three management systems at a research site near Nashua, Iowa: continuous corn - chisel plow, corn-soybean - no-till and soybean-corn - no-till. Each system was analyzed for two different research plots that varied in soil type and slope gradient. Calibration was performed with 1995 measured tile drain flows while validation was carried out using measured tile drain flows for 1993-1994 and 1996-1997. In general, SWAT adequately tracked the measured tile drain flows, except that the peak flows were consistently under-predicted. Differences of 2 to 11% between the predicted and measured values and model efficiencies ranging between 0.47 to 0.67 were determined for the average annual simulated tile flows. The r2 values determined for the simulated monthly tile drain flows ranged from 0.70 to 0.97 for the calibration period and 0.49 to 0.67 for the validation period. The overall evaluation of the SWAT model indicates that the model has the capability of predicting subsurface flows satisfactory for different soil, slope, and weather conditions.