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Research project (§ 26 & § 27)
Duration : 2017-04-01 - 2020-03-31

Soil erosion processes are highly dependent on the rainfall energy which is a function of the size and falling velocity of raindrops. Interactions between raindrop size, velocity and shape, wind speed and the intensity of the thunderstorm control the power of the erosive storm. As raindrops increase in size, their terminal velocity and momentum increase. Increasing raindrop size increases their kinetic energy which affects soil detachment and transport processes. Limited data on raindrop characteristics are available; most studies were performed in a laboratory or field setting covering only a few storms. Objectives of this study are to 1) quantify and compare drop size distributions of rainfall events at comparable locations in Austria, Czech Republic, and New Zealand, 2) derive rainfall kinetic energy (KE) - intensity (I) relationships for rainfall erosivity estimation, 3) evaluate temporal/seasonal distribution of the KE-I relationship, and 4) investigate the relationship between rainfall erosivity and soil erosion. At several sites in Austria, Czech Republic and New Zealand disdrometers will be installed to determine the erosive force of rainstorms. Relationships between rainfall kinetic energy and intensity will be determined with respect to seasonal/monthly variability. For those sites with measured wind data, the impact of wind speed and direction will be evaluated. Next to the disdrometers small erosion plots will be installed to register the erosive force of the rainfall events. Based on the obtained results we will check and possibly modify and adapt the existing correlations between rainfall energy and soil detachment and transport.
Research project (§ 26 & § 27)
Duration : 2015-10-01 - 2018-09-30

As the demand for agricultural products and the occurrence of extreme weather conditions increase, the resources soil and water are more attracted by the public. Therefore, an adaptive land use as a preventative element for soil and water conservation gains in importance. Planning of adaptation strategies are often based on the application of numerical models. With these models, the impact of hypothetical changes in land use under recent and changing climatic conditions on plant growth and water balance components can be estimated and evaluated. As a pre-requisite in existing models, soil hydraulic properties are seen to be temporally constant. However, previous studies have shown that soil structure and with it the soil water retention and hydraulic conductivity functions change significantly as a result of land use. If the dynamics of soil structure are neglected, the uncertainty of the model results increases. This could lead to incorrect planning and a more resources-consuming land use. Therefore, the objectives of this study are a) to measure landuse-induced changes in soil structure and in the soil hydraulic properties and b) the implementation of the results into hydrological models that quantify the changes using mathematical equations. These equations describe temporal changes of soil water retention and hydraulic conductivity based on the evolution in the soil pore-size distribution for different land use pratices (e.g., soil tillage, crop rotation, afforestation). To derive general principles for the influence of land use on hydrologically relevant soil properties, we will analyze comparable land use practices with similar soils along a climatic transect from Brandenburg to Styria. For the characterization of the soil hydraulic properties, field methods (hood infiltrometer and dye tracer experiments) will be combined with laboratory methods (transient evaporation experiments). This approach allows a better differentiation between macropore and matrix flow domains, which may be fundamental for the development of functions describing land use-induced changes of the soil pore space. We expect that the different land use measures will have a stronger influence on the macropores. The study will increase our knowledge about soil pore space changes under different land use pratices. Basing on a better understanding of the involved processes we will develop methods and models that are able to quantify the impact of an adaptive land use on the soil hydraulic properties, on components of the water cycle (soil water capacity, groundwater recharge, water quality), and on the production of biomass. This will be the basis for the development and assessment of sustainable land use systems.
Research project (§ 26 & § 27)
Duration : 2013-07-01 - 2014-06-30

Using the simulation model HYDRUS water movement from loamy to clayey soil, which is affected by preferential flow, will be simulated. In various depths moisture content and suction head will be measured by sensors. To complete the simulation with HYDRUS inverse modelling will be employed to estimate the unknown parameters and boundary conditions. The feasibility of detecting and quantifying the preferential flux at different depths during rapid percolation events will be explored. Further, the results of this research will make it possible to improve the estimate of water balance and water pollution risk in similar soils, especially in regions affected by intensive agriculture or mining.

Supervised Theses and Dissertations