Project number: J2-4489
Project duration: 36 months (1. 5. 2023 – 30. 4. 2026)
Cofinancing: Slovenian Research And Innovation Agency (100 %)
Lead partner in Slovenia: Faculty of Civil and Geodetic Engineering, University of Ljubljana
The research project will bring together three research organisations, namely the Faculty of Civil Engineering and Geodesy of the University of Ljubljana (UL FGG), the Slovenian Forestry Institute (GIS) and the Technical University of Vienna (TUW), to pool their knowledge and experience in the field of interception and erosivity of rainfall and to use it for the successful implementation of the research project. The main objective of the project is to build on the knowledge of interception of rainfall by different vegetation types and the impact of interception on rainfall erosivity based on high frequency measurements on existing research plots. Knowledge on this topic will be particularly important in the future, when more frequent and intense rainfall events with high erosivity can be expected due to climate change. Research on rainfall interception is important in both natural and urban environments. Urban trees reduce surface runoff by intercepting rainfall, influence evaporation and infiltration of retained water, reduce CO2, etc. All of the above could lead to their increased use as part of green infrastructure in the future. In natural environments, precipitation interception and thus erosivity of precipitation is one of the most important parameters of soil erosion, which can have, among other things, negative impacts on agriculture due to the loss of fertile soils. However, many scientific questions are still open in the field of rainfall interception and erosivity, due to the different vegetation types and their unique characteristics and the influence of seasonality.
To achieve the objectives of the research project, extensive field measurements will be carried out in three different study plots, two in the urban environment of Ljubljana and one in a predominantly agricultural catchment in Lower Austria. The choice of these three sites will allow to build on existing research work and to combine the knowledge and experience of all three partners. In both locations in Ljubljana, trees play an important role as part of the green infrastructure. UL FGG is already carrying out measurements in an urban park, where we are measuring individual elements of rainfall interception under two tree species where the tree canopy does not overlap. GI is already taking measurements in a mixed urban forest. The project will additionally measure raindrop microstructure (DSD) above and below the tree canopy using optical disdrometers at both locations. As interception of precipitation depends on many factors, meteorological (e.g. air temperature, wind) and vegetation variables (e.g. leaf area index) will also be measured in parallel at both plots at different times of the year. In the Lower Austrian catchment, no rainfall interception measurements have been carried out so far. However, measurements of precipitation and meteorological variables have been carried out. Intensive sediment measurements are also already being carried out. As part of the project, measurements of raindrop microstructure (DSD) using optical disdrometers above and below selected crop plants and conventional measurements of intercepted precipitation will be added.
Based on the data and extensive analyses, we will try to answer a number of open scientific questions, such as the influence of different meteorological variables on the microstructure of precipitation and intercepted precipitation under different climatic conditions, the influence of the interception process on the DSD of intercepted precipitation under different vegetation types in different phenological phases, what is the influence of the interception process on the erosive power of raindrops. The collaboration of researchers from all three partners and the comparison of the results of the analysis of high frequency measurements under different natural conditions in terms of climate, vegetation and soil is certainly an innovative research approach.
The key objectives of the research project are:
- To identify the influence of different meteorological variables (e.g. rainfall amount, intensity and duration, wind speed and direction, air temperature, humidity) on the DSD of open and intercepted precipitation under different climatic conditions. For this purpose, simultaneous and high frequency (1-minute time step) measurements of meteorological variables and the microstructure (DSD) of precipitation above and below vegetation will be carried out in experimental plots/sub-basins in Slovenia and Austria.
- To identify the influence of interception of precipitation by different vegetation types (different tree and crop species) on the DSD of intercepted precipitation in different seasons or phenophases. For this purpose, simultaneous and high-frequency (1-minute time step) measurements of the microstructure (DSD) of precipitation above and below two tree species, namely birch (Betula pendula Roth. ) and black pine (Pinus nigra Arnold), above and below urban mixed forest trees, as well as above and below selected crops (e.g. maize, wheat, barley).