Plot scale continuous modelling of runoff in a maize cropping system with dynamic soil surface properties

The evaluation of the hydrological impact of crop management practices requires models sensitive to temporal changes in surface properties and especially to changes in surface roughness and saturated hydraulic conductivity. This study reports on the development and application of a new, continuous, physically-based, spatially-distributed and plot-scale runoff model that required only five adjusted parameters. The results of the model were compared with runoff measurements taken over two years on 90 m2 runoff plots in a continuous maize cropping system with and without winter cover crop. On the basis of the daily predicted runoff, the model gave good fits for the intercropping period (Nash–Sutcliffe efficiency coefficient from 0.80 to 0.94) and poor to reasonable fits for the maize period (Nash–Sutcliffe efficiency coefficient from less than 0 up to 0.33). The poor results are in part attributed to the fact that only decreases in hydraulic conductivity can be modelled at present, whereas this property may in reality increase over time in some cases. Moreover, runoff hydrograms for individual storms are relatively well predicted dynamically. The large impact of semi-permanent wheel tracks on runoff production is also pointed out. Finally, a sensitivity analysis is performed and the relevance of incorporating dynamic soil properties in continuous modelling of runoff is underlined.