The use of artificial rainfall simulation (ARS) is a common method to study the interaction of soil and water (Strauss et al. 2000). Traditionally, precipitation simulation has been used as a tool to assess and determine the importance of surface runoff, usually with reference to soil erosion. Large-scale experiments are generally rare, although they are an efficient way to obtain directional soil hydraulic properties that functionally average local heterogeneities. Flow processes in the subsurface are usually measured indirectly. Such non-destructive methods for measuring subsurface flow processes often rely on soil moisture measurements or other indirect geophysical measurements (ERT, EMI, GPR,...) often accompanied by isotope or tracer analyses. Direct measurement of subsurface rainfall runoff involves considerable effort and cost, and in some cases, it is even impossible e.g., when it is not possible to dig a drainage ditch. At BFW - Department of Natural Hazards, about 150 representative plots in the Eastern Alps have been irrigated over the last 30 years using portable sprinkler systems for large plots (50 to 400 m²). In total, more than 350 rain simulation trials have been conducted. Specifically, this BFW rainfall simulation database contains data from 11 plots and 21 experiments where subsurface storm runoff was directly quantified. The results derived from these eleven test plots basically confirm the often-observed bimodal nature of subsurface flow, consisting of preferential/macropore flow and flow through the soil matrix (e.g., Weiler et al. 2005, Dasgupta et al. 2006, …). Preferential flow paths are mostly attributable to heterogeneities in the soil. Preferential macropore flow can be differentiated by means of such various types of heterogeneities. Four specific categories may be distinguished: phytogenic macropores (e.g. cavities left by decomposing roots); zoogenic macropores e.g. mole burrows, mouse holes); geogenic heterogeneities (e.g. periglacial cover beds, bedrock fissures and cracks) and anthropogenic heterogeneities (e.g. drainage systems, tillage pans). Each of these four categories is covered by at least one experiment in the BFW data record. The observed subsurface hydrographs provide insight into the process-dependent differences in precipitation-infiltration-subsurface runoff response. In a research group currently applied for at the DFG (SSF Research Unit), new and novel irrigation experiments for the measurement of subsurface stormflow will be carried out in four test areas and the existing ones from the BFW database will be reanalyzed and modeled. Keywords: infiltration, subsurface stormflow SSF, artificial rainfall simulation ARS
