Surface runoff is the fastest route from field to stream and the main transport route for sediment and adsorbed contaminants, and as such an important cause of surface water contamination in agricultural areas. The goals of the study were to explain differences in measured surface runoff volumes and nutrient loads of surface runoff between fields on the basis of characteristics of their meso- and microtopography, and to investigate the representativeness of plot scale measurements for the surface runoff behaviour of the whole field. The surface runoff measurements were performed at grassland, an arable field and a horticultural field. We combined these measurements with detailed topographic data at meso- and microscale. The nutrient concentrations measured in the surface runoff were high, especially on the grassland. The differences in nutrient loads were caused both by differences in surface runoff volume and in nutrient concentrations in the soils of the fields. However, the overall estimated yearly nutrient load from surface runoff was lower than expected from similar studies. The effect that microtopography has on flow route shapes in flat fields can be quantified with metrics from surface runoff curves. We performed simulations with the FAST-Runoff model for coupled instantaneous redistribution of water over a heterogeneous surface and infiltration and 2D groundwater flow. The simulations showed that ponding evolved unevenly throughout the fields, suggesting different times of activation of the flow routes within the fields. Unfortunately, this spatial variability could not be linked to the full meso- and microtopographies of the fields, because the non-linearities introduced by the dynamic specific yield, could only be treated at very small timesteps resulting in very long computation times
|Title of host publication||Water redistribution at the soil surface, ponding and surface runoff in flat fields|
|Place of Publication||Wageningen|
|Number of pages||154|
|Publication status||Published - 2013|
Appels, W. M., Noij, I. G. A. M., & Massop, H. T. L. (2013). Spatiotemporal variability of saturation excess surface runoff in flat fields due to interactions with meso- and microtopography. In W. M. Appels (Ed.), Water redistribution at the soil surface, ponding and surface runoff in flat fields (pp. 75-98).