Supplementing rainfall simulator studies with single drop measurements

Rainfall simulators are essential tools for geoscientific and hydrological research, e.g. water erosion processes, throughfall phenomenon, interception etc. They allow the creation of suitable and reproducible experimental conditions providing a large amount of information. However, in certain situations, e.g. the soil splash phenomenon, other research methods are needed to study the basic processes and mechanisms on a smaller scale, i.e. concerning the interaction of single drops. In such a case, single drop measurements used with raindrop generators can be a good complementary tool for rainfall simulators. They provide complete understanding and description of the investigated phenomenon. The aim of this study was to present selected measurement methods based on the single drop methodology which are used to investigate splash erosion and surface deformation, interaction of drops with leaves or conifers, and microorganism transportation. These include: a) a set of high-speed cameras with PTV (Particle Tracking Velocimetry) software used to identify, track, and characterize the splashed particles and water droplets; b) splash cup measurements for the determination of the mass ratio of splashed particles during the raindrop splash phenomenon; c) a 3D surface scanner and microtomography for the description of surface deformation after the drop impact; d) a laser diffraction method and light microscopy for the determination of the size of splashed particles; e) IRMS (Isotope-ratio mass spectrometry), i.e., deuterium-labelled water used to the define the origin of the splashed water.   This work was partly financed from the National Science Centre, Poland; project no. 2022/45/B/NZ9/00605.   References: Beczek M., Ryżak M., Sochan A., Mazur R., Polakowski C., Hess D., Bieganowski A.: Methodological aspects of using high-speed cameras to quantify soil splash phenomenon. GEODERMA 378, 2020 Mazur R., Ryżak M., Sochan A., Beczek M., Polakowski C., Przysucha B., Bieganowski A.: Soil deformation after one water-drop impact – The effect of texture and soil moisture content. GEODERMA 417, 2022 Ryżak M., Beczek M., Mazur R., Sochan A., Gibała K., Polakowski C., Bieganowski A.: The splash of a single water drop on selected coniferous plants. Forest Ecology and Management 541, 121065, 2023