Rainfall-runoff models compared for tile-drained agricultural fields in the Western Lake Erie Basin, Ohio

Simple models like the curve number method are commonly used to predict runoff volumes from agricultural fields, playing a key role in nutrient transport modeling and watershed management; however, the curve number method has not been evaluated for use in tile-drained fields and it may therefore produce erroneous runoff predictions if applied in these settings. In this study, we evaluate the curve number method at 12 tile-drained research sites in the Western Lake Erie Basin of Ohio. Rainfall and runoff observations at each of these sites were used to calculate curve numbers using six published variations of the curve number method. These were compared to published curve numbers, selected from NRCS tables to correspond to land use in the study sites. In addition to the curve number methods, the complacent-violent method was also used to develop runoff model parameters for the research sites. Methods were compared to one another using Nash-Sutcliffe efficiency, bias, and R-squared. The curve number methods often performed poorly, and sometimes altogether failed to produce a real solution. Of the rainfall-runoff models evaluated, the complacent-violent method produced the most accurate results and should be used in place of the curve number method to make runoff predictions from tile-drained fields.