Influence of spatial variations of microtopography and infiltration on surface runoff and field scale hydrological connectivity

Surface runoff on agricultural fields arises when rainfall exceeds infiltration. Excess water ponding in and flowing through local microtopography increases the hydrological connectivity of fields. In turn, an increased level of hydrological connectivity leads to a higher surface runoff flux at the field boundaries. We investigated the functional hydrological connectivity of synthetical elevation fields with varying statistical properties. For this purpose, we developed an object-oriented ponding and redistribution model to which Philip’s infiltration model was coupled. The connectivity behaviour is determined by the presence of depressions with a large area and spatial organization of microtopography in rills or channels. The presence of microdepressions suppresses the effect of the spatial variation of infiltration properties. Connectivity behaviour of a field with a varying spatial distribution of infiltration properties can be predicted by transforming the unique connectivity function that was defined for a designated microtopography.

Research highlights
► The development of surface runoff in flat areas was investigated in a framework of hydrological connectivity.
► Ratios of statistical properties of microtopography and water level at a field can be interpreted as measures of hydrological connectivity in combination with simplified hydrographs.
► The development of hydrological connectivity on infiltrating surfaces is identical to that of non-infiltrating surfaces when the spatial distribution of soil hydraulic properties has smaller spatial correlation characteristics than the spatial distribution of microtopography.